Establishing Geochemical Constraints on Mass Accumulation Rates
Across the Cretaceous-Paleogene Boundary With Extraterrestrial
Helium-3
by
Marie Minh-Thu Giron
B.S. Geology
California Institute of Technology, 2009
SUBMITTED TO THE DEPARTMENT OF EARTH, ATMOSPHERIC AND
PLANETARY SCIENCES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
MASTER OF SCIENCE IN EARTH AND PLANETARY SCIENCES
at the
UILJh
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
SEPTEMBER 2013
©2013 Massachusetts Institute of Technology. All rights reserved.
Signature of Author:
Earth, At
Depart ef
eric and P anetary Science
13
August 26
Certified by:
(3
Roger E. Summons
Professor of Geobiology
Thesis Supervisor
Accepted by:
Robert van der Hilst
Department Head of Earth, Atmospheric and Planetary Sciences and
Schlumberger Professor of Geophysics
1
This page intentionally left blank.
2
Establishing Geochemical Constraints on Mass Accumulation Rates Across
the Cretaceous-Paleogene Boundary With Extraterrestrial Helium-3
by
Marie Minh-Thu Giron
Submitted to the Department of Earth, Atmospheric and Planetary Sciences
on August 26, 2013 in Partial Fulfillment of the Requirements for the
Degree of Master of Science in Earth, Atmospheric and Planetary Sciences
Abstract
Records of ocean biogeochemistry in marine sediments show shifts across the
Cretaceous-Paleogene boundary (K-Pg) that are simultaneous with the extinction event
and onset of the boundary clay deposition. However, the timescale of these records is
difficult to determine near the boundary because of fluctuating sedimentation rates and
the short duration of the event. In this study, we have used extraterrestrial helium-3 as a
constant flux proxy for instantaneous mass accumulation rates in four marine sections:
Caravaca, Spain; El Kef, Tunisia; and Hojerup and Kulstirenden, Denmark. These
sections are characterized by a thick boundary clay layer and, therefore, are more suitable
than many other proxies for high-resolutions studies. In order to better understand the
extent of the impact-related perturbations in different paleoenvironments, we performed a
high-resolution analysis at Caravaca and lower-resolution analyses at the other three
sections. We find that Hojerup and Kulstirenden are not suitable for this analysis due to
the probable variation in the flux of extraterrestrial helium-3 as a result of lateral changes
in sedimentation rate. Our results suggest that carbonate burial, and likely carbonate
production, were more severely affected with increasing paleolatitude. However, the
unique depositional environments are probably much more important than just
paleolatitude alone. We calculate boundary clay durations of Caravaca and El Kef of
6.45 (h 0.86) kyr and 6.28 (± 1.03) kyr, respectively. These results are consistent with
other studies and indicate a uniform, global deposition of the boundary clay and a rapid
recovery of carbonate burial in the marine ecosystem after the Cretaceous-Paleogene
extinction event.
Thesis Supervisor: Roger E. Summons
Title: Professor of Geobiology
3
This page intentionally left blank.
4
Acknowledgements
There are many people whom I need to thank for contributing to my growth as a scientist
and engaged citizen of the world. I would first like to thank my thesis supervisor, Roger
Summons, for giving me the opportunity to study at such a unique and stimulating
institution. I learned a great deal working in E25, and the lessons learned are not limited
to the earth sciences. I am grateful to my mentor, Julio Sepinlveda, for introducing me to
the wonderful world of the Cretaceous-Paleogene and patiently supporting and teaching
me. I am extremely thankful for the experiences I had in the field in Tunisia and Spain
that he made happen. I thank Sujoy Mukhopadhyay for advising me on this project,
analyzing my samples, and allowing me to expand my skill set. I would also like to
thank David McGee for being available as a resource and providing useful feedback.
I can say without a doubt that this thesis would not have been completed on time without
the support of my thesis-writing buddies, Sara Lincoln and Alex Evans. I am eternally
grateful that Sara has been my mentor, advocate, big sister, and friend, and I cannot
imagine having gone through this experience without her. I am thankful to Alex
introducing me to the MIT Graduate Student Council, an experience that has changed my
career plans if not my life. I thank him for showing me what true productivity and hard
work look like and for working by my side during the daytime and occasionally through
the night.
I thank my Graduate Student Council family for opening my eyes to the fulfillment that
results from passion and service. My experience serving on the GSC lit a fire in me, and
I hope that fire never dies. I especially thank my Activities Co-Chair, Alex Guo, for
being a friend and sister. I have never enjoyed working with a partner so much, and I
hope this is not the end of our partnership.
I am lucky to have such wonderful friends, and I thank all of them for making me smile
and take a break from perfecting my stress lines. I thank my roommates, Cristina
Camayd, Michelle Lira, and Monika Avello for their patience, love, and support. I thank
Bomy Lee Chung, Angela Laurance, Florence Schubotz, Helen Feng, Sharon Newman,
Ross Williams, Yodit Tewelde, and Ruel Jerry for being great friends, especially during
stressful times.
I finally thank my family for their support and unconditional love.
5
This page intentionally left blank.
6
Table of Contents
Chapter 1: Introduction..............................................................................................
Cretaceous-Paleogene M ass Extinction..................................................................
M arine Ecosystem Recovery ....................................................................................
Outline of Thesis...................................................................................................
Chapter 2: AnalyticalBackground...........................................................................
Extraterrestrial Helium -3 .......................................................................................
A pplication of the Extraterrestrial Helium -3 Proxy..............................................
Chapter 3: Experimental Procedures......................................................................
Sam ple Background...............................................................................................
Sample Preparation..............................................................................................
H elium Analysis...................................................................................................
Chapter 4: Cretaceous-PaleogeneSections .............................................................
Caravaca, Spain.........................................................................................................
El Kef, Tunisia
................................................
Stevns K lint, D enm ark..........................................................................................
Chapter5: Results and D iscussion..........................................................................
Caravaca, Spain.........................................................................................................
El Kef, Tunisia
................................................
Hojerup, Denm ark.................................................................................................
Kulstirenden, D enm ark ..........................................................................................
Conclusion....................................................................................................................
References.....................................................................................................................
Appendix .......................................................................................................................
7
9
9
12
14
15
15
18
21
21
23
24
27
28
30
32
37
41
46
50
52
65
67
73
This page intentionally left blank.
8
Chapter 1: Introduction
Cretaceous-PaleogeneMass Extinction
The Cretaceous-Paleogene (K-Pg) mass extinction event is the most recent of
Earth's 'big five' Phanerozoic mass extinction events and occurred 66 million years ago
(Figure 1) [1-3]. Evidence for the global K-Pg extinction event is clearly seen in the
fossil record with the disappearance of Mesozoic species and the appearance of Cenozoic
species, and it is estimated that at least 60% of all species went extinct within just a few
million years [4]. Groups that underwent severe extinction include calcareous
nannoplankton [5], planktic foraminifera [6], and dinosaurs [7]. This mass extinction
was a critical event in the history of the Earth and changed the course of biological
evolution.
The most significant trigger of the extinction is widely accepted to be a bolide
impact that struck near the present day Yucatan Peninsula and formed the Chicxulub
Crater (Figure 2) [4, 8]. Evidence for this catastrophic and contemporaneous impact is
seen worldwide in marine sediments and includes the famous iridium anomaly
discovered by Alvarez et al. [9]. The presence of ejecta spherules, Ni-rich spinels, and
shocked minerals also support an extraterrestrial impact, and they are found in the highest
concentrations nearest the Chicxulub Crater [4]. The prolonged eruption of the Deccan
Traps in India and the resulting environmental effects may have also contributed to the
mass extinction [10]. The extraterrestrial impact had global effects, the most immediate
of which was the injection of dust and aerosols into the atmosphere [11]. The impact
ejecta and the sulfur aerosols formed from volatilization of impacted anhydrite deposits
9
600
550
J
Late Ashgillian
0
Soo o
450 0
WC
0
2
Late Norian
(end Triassic)
4
Late Frasnian
(Late Devonian)
2
400
Maastrichtian
(end Cretaceous)
(end Permian)
(end Ordovician)
L
5
Djhulfian
50
0) 250
0
~20
150 0
IA
o
A
L EL
B M[
100
S00
11
~
0
~ ~
01~~~
S
Ord
o
o
q
Dev
0
q#~
~
0
t
C~30)
0
0
0* 0
Q
C
(0
0
N
N
0
N
0
N
01-
tO'*-0
-
-
-
Cret
Jur
Tri
Perm
Carb
0
-
.
.
0
0--
N
Pgn
N
Millions of Years Ago
Figure 1. Diversity throughout the Phanerozoic. Arrows point to the 'big five' mass
depletions and extinctions. Figure taken from Bambach et al., 2004 [12].
drastically reduced the intensity of solar insolation at the Earth's surface [11]. This
resulted in a transient devastation to primary productivity [11] and possible nutrient
scarcity at higher trophic levels [13], although this continues to be much debated [14].
Another proposed factor that contributed to decreased insolation was soot produced by
widespread wildfires [15]. The resulting 'nuclear winter' caused short-lived cooling [16],
contributing to ecosystem instability.
Another proposed effect of the impact was acid rain resulting from the regional
production of nitrous and nitric acid by both heating of the atmosphere [17] and wildfires
[18] and from the production of sulfuric acid from the sulfate aerosols mentioned above
[11]. Local weathering [17] and surface ocean acidification [14] may have increased as a
result of the acid rain, making some environments toxic. The immediate effects of the
10
impact lasted for a decade or less [11], but there were longer-lived catastrophic effects on
the biosphere that persisted for an extended period [19].
B
Very proxima
Guwal, S
x
MOmWi NE
,
Muad
4
Cheo
Unk
Ag
Sp n
4,
7
I
YAI kinior
~
0
3--~2
30
Ip1
1;u-IiIFL
(Mn)
WecCW
-Mad
Red Uunr clay
Clay
M*ri
Elass uuri
* shoSdud
mtwow
Limeskxne
* N~i-ch sPineis
o Ejeta spherules
Igneous cass
* Accrefony hapE
IddUM
I
Figure 2. A shows global distribution of K-Pg sites studied, and B shows typical
depositional sequences based on proximity to the Chicxulub crater. Figure taken from
Schulte et al., 2010 [4].
11
Marine Ecosystem Recovery
Several marine geochemical records across the Cretaceous-Paleogene boundary
(K-Pg) show pronounced shifts coincident with the extinction horizon, but they are
accompanied by varying rates of recovery back to pre-boundary values. Geochemical
changes at the boundary include a negative carbon isotopic excursion in bulk carbonates
[4] and in specific calcareous organisms [20], a minimum in calcium carbonate percent, a
maximum in total organic carbon (TOC), and a shift in the distribution of lipid
biomarkers (Figure 3) [21]. Carbon isotope records of planktic and benthic foraminifera
imply that the biological pump in the open ocean did not recover fully for at least 3
million years [20]. However, the biomarker record recovers more quickly, consistent
with the benthic foraminiferal [14] and biogenic barium records [22]. Current estimates
from the biomarker record suggest that marine primary productivity recovered in less
than 10,000 years, although the community distribution changed [21]. When
investigating changes on such short timescales, it is necessary to have a precise, highresolution geochronology.
In addition to constraining recovery intervals, it is also useful to understand the
recovery trends in the accumulation rates of sediments and other parameters, i.e. whether
they are linear, step-wise etc. The geochronology of the immediate aftermath of the
extinction event is not well constrained because mass accumulation rates are not likely to
be constant across the K-Pg [23]. Therefore, sedimentation rate estimates in the
underlying Cretaceous and overlying Paleogene sediments cannot be assumed for the
boundary interval. By comparing the trends of sediment, carbonate, and biomarker
12
accumulation rates in different depositional environments, we may be able to better
understand environmental changes and kill mechanisms in the ocean.
% TOC
0.0 0.5
1.0
C/C2 Steranes
8'6 N, (%)
1.5
-5
5
0
0.5 0.6 0.7 0.8
10
i* &
~
401~
4
4
L
C
B
A
I
D
E
F
E
31
0
0
E
9
0
0
21
I
I
0
-5
H-28
~3MftcbyL~mmnmnesofl.
I--i-26
6'C,
-24
0.1I 0.2 0.3 0.4
S/(S+H)
(%o)
2
4
6
8
10
2-MeHI (%)
Figure 3. Geochemical and lipid biomarker records through the K-Pg boundary at
Kulstirenden, Denmark. The percent of total organic carbon (A) returns to preboundary
values much slower than the S/(S+H) ratio (D), which measures the relative changes of
eukaryotic and bacterial contributions to biomarker profile. S/(S+H) is an abbreviation
for C27-29 steranes/(C 27-29 steranes + C30-35 hopanes). Figure taken from Sepdlveda et al.,
2009 [21].
13
In order to study these trends, we studied four Cretaceous-Paleogene boundary
sections with different marine paleoenvironments: Caravaca, Spain; El Kef, Tunisia; and
Hojerup and Kulstirenden, Denmark. We measured the extraterrestrial helium-3 content
in samples from these sections and used it as a constant flux proxy for instantaneous mass
accumulation rates (MARs) in order to constrain the intervals of boundary clay
deposition and post-impact timescales. We performed a high-resolution analysis of
helium isotope ratios within the boundary clay at Caravaca and lower-resolution analyses
at El Kef, Hojerup, and Kulstirenden.
Outline of Thesis
The following sections detail the use of the extraterrestrial helium-3 constant flux
proxy for studying the Cretaceous-Paleogene boundary interval at four sections with
different paleoenvironments. Chapter 2 describes how the proxy works and why it is
suitable to use at the Cretaceous-Paleogene boundary. Chapter 3 describes the
experimental procedures and methods used for sample preparation and analysis.
Chapter 4 describes the sections studied, and the results are presented in Chapter 5.
Finally, I summarize my findings and present conclusions with future directions.
14
Chapter 2: Analytical Background
ExtraterrestrialHelium-3
When Alvarez et al. (1980) investigated iridium in the boundary clay of various
K-Pg sections, the intent was to employ Ir concentrations as a proxy for mass
accumulation rates (MARs) in order to determine the length of time represented by the
boundary clay [9]. It had previously been suggested that meteoric dust was a potential
source of platinum group elements (PGEs), including iridium, in sediments [24].
Additionally, concentrations of Ir in marine red clay were shown to be inversely
proportional to sedimentation rates suggesting that there was a homogeneous flux of Ir to
sediments [25]. The Alvarez team discovered an Ir anomaly that was coincident with the
K-Pg boundary and mass extinction, therefore making Ir concentrations unusable as a
proxy for MARs. It is now known that this anomalous Ir originated from the bolide
impactor that triggered the mass extinction [4]. However, the concept of inferring MARs
from elemental concentrations is usable if there is a constant flux of the element or
isotope with no spike from the asteroid impact or other sources within the time interval of
interest. Such proxies are referred to as constant flux proxies (CFPs) and include helium3 derived from extraterrestrial sources [26, 27]. Extraterrestrial helium-3 is delivered to
the Earth via interplanetary dust particles [28].
Interplanetary dust particles (IDPs) derive from asteroid and comet debris, and
IDP sizes range from 0.1 to 1 mm [29, 30]. Drag from the Poynting-Robertson effect and
the solar wind causes IDPs to spiral towards the sun with a lifetime of about 104 to 101
years [31, 32]. As they orbit, IDPs are exposed to solar wind, solar flares, and solar
energetic particles, which implant helium with high isotope ratios ( 3He/ 4He) into the
15
4
3
surface of the IDPs [28, 33, 34]. IDPs have significantly higher He/ He values (on the
order of 10~4) than those of terrestrial helium sources (on the order of 10-8) [35, 36], and
3
we refer to the implanted 3He as extraterrestrial helium-3, or HeET- It is important to
note that although asteroids are prone to helium implantation, they are very unlikely to
deliver 3HeET to Earth's surface because they release volatiles during atmospheric entry
and impact breakup and the
3He
is not retained in the Earth's atmosphere [26, 37].
IDPs continuously enter the Earth's atmosphere and rain down to the surface, but
only a small fraction retains 3HeET due to size-dependent atmospheric entry heating [37].
Helium loss has been experimentally shown to occur between -550 and -700'C, and
modeling suggests that -0.5% of integrated IDP surface area is heated to less than 600'C
during atmospheric entry, likely retaining trapped volatiles [35, 37]. Sieving experiments
suggest that at least 80% of 3 HeET is delivered to the Earth by IDPs less than 53 Pm in
diameter [37-39]. This is consistent with a theoretical peak mass flux of IDPs entering
the atmosphere below 650'C at a diameter of-20 pm [37]. Some IDPs settle out on the
seafloor where they are incorporated into the sediment, and those that are He-bearing
impart their 3 He-enrichment to the sediments [37]. Seafloor sediments dating back tens
of millions of years and even to the Ordovician (-480 Ma) have proven to be effective at
retaining 3 HeET, and this allows the utility of helium isotope ratios in studying sediments
near the K-Pg boundary [26, 40]. Because 3HeET is predominantly delivered to Earth by
IDPs, 3 HeET concentrations can be considered a record of IDP flux [26, 38, 41].
Furthermore, since the flux of 3 HeET to marine sediments is relatively constant over -Myr
intervals, 3 HeET can be used as a constant flux proxy [42, 43].
16
Marine sediments also contain terrigenous helium enriched in 4He, and proposed
sources include the mantle, atmosphere, and crust [44-47]. The mantle and atmosphere
likely contribute insignificant amounts of 3He to marine sediments [44, 45]. Spallation
reactions between cosmic rays and surface rocks can also produce 3He, although this also
makes a negligible contribution [46]. Radiogenic helium with relatively low 3 He/ 4 He
values is produced in crustal rocks through radioactive decay, where 3 He is produced by
the reaction 6 Li(na) 3H-
3
He, utilizing neutrons from the U and Th decay reaction that
produces 4He [40]. This is thought to be the most significant terrestrial source of helium
[47]. Therefore, we assume that helium in the sediments studied represents mixing of
two isotopic end-members, the contributions of which can be determined by simple
binary modeling [40]. The 3He/ 4He value of the extraterrestrial end-member can be
estimated using the average measured helium isotope ratios of the solar wind (4.3x1 04
[48]) and of stratospheric IDPs (2.4x10- 4 [49]), and the 3 He/ 4He value of the terrestrial
end-member can be estimated from crustal rocks (<2.23x10- [26, 47]).
Assuming a constant flux of IDPs to the Earth, the concentration of 3 HeET in
sediments will be sensitive to fluctuations in MARs, which makes the 3 HeET constant flux
proxy ideal for studying the MAR changes through the K-Pg. This proxy can provide
high-resolution records of instantaneous mass accumulation rates in sediments that were
deposited in dynamic environments. Mass accumulation rates change across the K-Pg
within a short amount of time as a result of the mass extinction, and this proxy allows us
to see details in the K-Pg boundary clay that would be erroneous if we assumed average
MARs determined by age models. MARs can also be determined using the
which uses the excess
23 0
230
Thxs proxy,
Th (formed from 2 3 4 U in the water column) measured in
17
3
sediments to determine MARs, and this proxy is consistent with the HeET proxy [27].
However, due to the relatively short half-life of 23 0Th, this proxy is unusable for studying
3
sediments older than 500 ka [36, 50]. On the other hand, He is a stable isotope that can
be used to study sediments that are millions of years old, e.g. at the Cretaceous-Paleogene
boundary at 66 Ma [23] and the Paleocene-Eocene Thermal Maximum at 55 Ma [51].
The 3HeET proxy is also ideal for our study because there is no increase in 3 HeET flux
around the K-Pg [23], unlike the Ir record [26].
Application of the ExtraterrestrialHelium-3 Proxy
In order to use 3 HeET as a proxy for instantaneous MARs, several assumptions
3
must be made. First, we must assume that the flux of HeET to the seafloor,fHe, in the
area of interest was constant during the entire interval being studied.
3
HeET fluxes in K-
Pg-age pelagic limestones in the Italian Apennines remain constant across the boundary,
allowing us to make this assumption for our study [44]. Second, we assume that the
retentivity of 3 HeET in sediments was also constant during the K-Pg interval because
HeET has been detected in -480-Ma-old sediments and retentivity is unlikely to change
3
over a few million years [32, 40]. The final assumption is that there are only two
contributing sources of helium, extraterrestrial and terrigenous, and, therefore, helium in
sediments can be represented by mixing of these two end-members.
When using this proxy to estimate MARs in a particular section, it is necessary to
estimate the product
OffHe,
the flux of 3 HeET, and R, the retentivity of 3 HeET, in addition
to measuring He isotope ratios (Equation 1). We refer to this product as impliedfHe, and
18
because we have assumed that both the flux and retentivity of 3HeET are constant across
the K-Pg, then we assume that impliedfHe at each site is also constant. However, implied
fHe is expected to vary between sites due to differences in sediment focusing and
retentivity. Since MARs fluctuate through the K-Pg boundary clay, we calculated the
impliedfHe at each site within the better constrained Maastrichtian stage at the end of the
Cretaceous, where average MARs can be determined using age models, and used that
estimate for the Danian stage at the beginning of the Paleogene. Because lateral transport
of sediments in the ocean can result in varying amounts of sediment focusing or
winnowing,fHe varies depending on the locality. This can present a significant challenge
in determining MARs and impliedfHe if the amount of sediment focusing or winnowing
in a particular section changes throughout the interval of interest. If the flux of 3 HeET
fluctuates due to changes in lateral advection of sediments, then the implied flux
calculated in the constrained interval and used in the more dynamic interval will not
result in comparable MARs for all parts of the section and the relative changes will not be
accurate. This problem will be expanded on further below.
19
The following relationships are necessary for using this proxy [43],
fHe - R
= a - [3HeET]
Equation I
Equation 2
a = SR - p
3
[ 3 HeET] =
4
He/ HeTERR
13 He/ 4 Hemeas
1
3
)
[3 Hemeas]
Equation 3
4
He/ HeRDP
where fHe is the flux of 3HeET to the sediment (cc STP cm-2 kyrI),
R is the dimensionless retentivity of 3HeET, varying between 0 and 1,
a is the sediment mass accumulation rate (MAR) (g cm-2 kyr-1),
3
[ 3HeET] is the concentration of HeET (cc STP g-1),
SR is the sedimentation rate (cm kyr'),
is the in situ sediment density (g cc'),
He/4 He is the helium isotope ratio,
and [3 Hemeas] is the measured concentration of 3He in the sample (cc STP g-1).
The subscripts 'TERR' and 'IDP' refer to the terrigenous and extraterrestrial endmembers. In order extract the contributions of the extraterrestrial and terrigenous endmembers, we must assume values for the end-member helium isotope ratios, 3He/HeTERR
and 3 He/ 4HeIDP, which, by convention, are normalized to the atmospheric helium isotope
ratio, RA
3
=
1.39 x 10-6. In this study, we have chosen 3He/HeTERR to be 0.03 RA and
He/ 4HeIDP to be 290 RA as has been done in previous studies [23, 44].
20
Chapter 3: Experimental Procedures
Throughout all experimental procedures, measures were taken to minimize the
risk of contamination. All non-sterile materials were cleaned with organic solvents, and
ceramic and glassware were combusted at a minimum of 450'C for 8 hours. All
materials were handled with clean nitrile or latex gloves.
Sample Background
Caravaca - Samples from Caravaca were obtained from Prof. Laia Alegret
(Universidad de Zaragoza). The stratigraphic height of the samples ranged from 850 cm
below to 20 cm above the K-Pg with 19 Cretaceous samples and 12 Paleogene samples, 8
of which were within the 10-cm boundary clay. Samples that were received as large
rocks (tens of grams) were broken with a hammer, and the smaller pieces were pulverized
with a mortar and pestle. Other samples had been previously filed, and in the absence of
rock samples, we used the filings from the previous study. Pulverization should not have
resulted in any He loss from the sediment samples [41]. Other researchers determined
the carbonate content in two different ways due to the availability of particular samples in
different laboratories. In all Paleogene samples and the two Cretaceous samples nearest
the boundary, the carbonate content was determined gravimetrically after HCl treatment
by Dr. Julio Sepulveda (MIT). Approximately 1 g of powdered sample was weighed and
treated with diluted HCl for at least 24 hours until no bubbling was observed. The
samples were then neutralized with water, centrifuged, dried at 60'C, and weighed. The
carbonate fraction was calculated as the difference between the initial and final weights
21
divided by the initial weight. The carbonate fraction of the remaining Cretaceous
samples was determined by measuring the amount of CO 2 produced from treating 1 g of
sediment with 50% HCl in the laboratory of Prof. Laia Alegret.
El Kef - Samples from El Kef were obtained from Prof. Laia Alegret. The
stratigraphic height of the samples ranged from 540 cm below to 120 cm above the K-Pg
with 3 Cretaceous samples and 7 Paleogene samples, 4 of which were within the 50-cm
boundary clay. Most of the samples were received either as filings or as powder
previously pulverized by a mortar and pestle. Remaining samples were received as large
rocks and were broken with a hammer before pulverization with a mortar and pestle. The
carbonate fraction for all samples was determined gravimetrically after HCl treatment by
Dr. Julio Sepnlveda.
Stevns Klint - Samples from Stevns Klint were obtained from Dr. Julio
Sepnlveda and were collected from two sites 8.5 km apart [52], Hojerup and Kulstirenden.
From Hojerup, we had 2 Cretaceous samples and 6 Paleogene samples, the stratigraphic
range of which was 51 cm below to 8.25 cm above the K-Pg. Of the Paleogene samples,
4 were from the 5.5-cm boundary clay. From Kulstirenden, 3 Cretaceous samples and 8
Paleogene samples spanned a range of 105 cm below to 45 cm above the K-Pg. Of the
Paleogene samples, 6 were from the 37-cm boundary clay. As with the other sections,
some samples were received as large rocks, and others were previously filed or
pulverized. Rock samples were crushed and pulverized with a mortar and pestle. Dr.
Julio Sepnilveda had previously determined the carbonate fractions for both sections
gravimetrically after HCl treatment.
22
Sample Preparation
Aliquots of the powdered samples were weighed on a Mettler Toledo AG204 0.1
mg-readability digital scale and transferred to sterile 50 mL centrifuge tubes for
decalcification. Due to the physical constraints of the sample injection system on the
isotope ratio mass spectrometer, we aimed for a target post-decalcification mass of 200
mg. The target pre-decalcification mass was calculated using the carbonate fraction, and
initial sample masses ranged from approximately 200 mg to 6 g. We prepared at least
two replicates of each sample.
Carbonate was removed from samples in order to analyze the maximum amount
of He-bearing sediment possible. Powdered samples were incrementally decalcified in
50 mL centrifuge tubes by the stepwise addition of 5 to 10 mL aliquots of 10% acetic
acid, which was chosen because acetic acid leaching does not have an effect on measured
3
He [40, 44]. After each aliquot of acetic acid was added, the centrifuge tubes were
capped and agitated either manually or by a vortex mixer until the sediment and solution
had mixed thoroughly. With the caps loosened to accommodate CO2 release, the tubes
were placed in an ultrasonic bath for 45 min to facilitate the reaction. These steps were
repeated at least 6 more times until carbonate digestion was visibly completed.
The tubes were centrifuged at 2750 rpm for 30 min, and the supernatant was
removed with a sterile plastic pipette. The sediment was washed twice with
approximately 50 mL of deionized water in order to dilute the remaining acid-water-salt
mixture. After each wash, the tubes were centrifuged and decanted as described above.
Occasionally, samples with extremely high carbonate content went through two rounds of
23
decalcification to ensure thorough carbonate digestion. Samples were considered to be
fully decalcified when sonication no longer produced CO 2 bubbles.
The sediment pellets were then frozen by dipping the centrifuge tubes in liquid
nitrogen and were transferred to pre-weighed tin foil cups using spatulas, which were
inserted into the pellets before the freezing process. The spatula-and-pellet 'popsicles'
were removed from the tubes, and with the assistance of tweezers, the pellets melted off
of the spatulas and fell into the tin cups. In order to recover any residual sediment in the
tubes, a few milliliters of deionized water was added to the empty tubes. The tubes were
placed in the ultrasonic bath for 30 min, and the second 'popsicle' was frozen and
transferred as described above. Tin cups and pellets were placed into an oven at 70-80*C
for 5-9 hrs so that residual water could be removed. As the samples dried, the tin cups
were crimped and packed to reduce the potential for sharp sediment edges that could
puncture the foil. Once dry, the tin cups were compacted into smooth balls and weighed.
Helium Analysis
Helium isotope ratios were measured in Prof. Sujoy Mukhopadhyay's lab at
Harvard University with a Nu Noblesse Noble Gas Isotope Ratio Mass Spectrometer
equipped with a multi-collector. The analytical methodology is very similar to that of
4
3
previous studies [40, 53]. An electron multiplier and Faraday cup measured He and He
abundances, respectively. Tin balls were fused in a radiatively heated vacuum furnace
heated up to 1400*C, and extracted gas was filtered with a charcoal trap and SAES
getters. A cryogenic cold-finger was used to trap the filtered gas, and He was released by
24
heating the cold-finger to 32 K and was directed to the mass spectrometer for helium
detection. Only 39% of the extracted gas was analyzed in order to avoid saturation of the
detectors.
Blanks were also analyzed in this manner in order to test for background
contamination. High Helium 3, an isotopic standard with a helium isotopic ratio of 8.8
RA, was measured and used to convert signals from the detectors into total amounts of
He and 4He. For each sample of a particular stratigraphic height, 3 He/ 4He was
3
determined by dividing the sum of 3He in all replicates by the sum of 4He in all replicates.
The concentration of 3 HeET was calculated using Equation 3 and used to estimate
instantaneous MARs using the impliedfHe determined by Cretaceous samples.
ImpliedfHe estimates were determined for each site by multiplying the mean Late
Maastrichtian [3 HeET] by the independently determined MAR. The l
[ 3 HeET] iS equal to
20,
uncertainty of
where N is the number of replicates analyzed per sample [44].
The error of mean [3 HeET was calculated by the following,
6mean
Equation 4
.2
where (T is the 1y uncertainty of [3 HeET] for a given sample and n is the number of
samples [23]. Average Maastrichtian sedimentation rates were calculated using different
age models in each of the sections, which are discussed below.
25
This page intentionally left blank.
26
Chapter 4: Cretaceous-Paleogene Sections
The marine sections investigated in this study are Caravaca, Spain; El Kef,
Tunisia; and Stevns Klint (Hojerup and Kulstirenden), Denmark. These three localities
vary in paleolatitude and paleodepth, allowing us compare our results in sections with
different paleoenvironments (Figures 4-5).
Figure 4. Paleogeography of sections studied. Map modified after Scotese [54].
atmosphere
Stevns Klint (100-150m)
El Kef (200m)
Caravaca (600-1000m)
continent
ocean
Figure 5. Relative paleodepths of study sections [55-57].
27
W-
Caravaca,Spain
The K-Pg section at Caravaca in southeastern Spain (Figure 6) is one the most
complete sections that is studied [58] and was deposited in a middle-bathyal
paleoenvironment at a paleolatitude of 27*N [59]. The paleodepth is estimated to be 6001000 m based on the benthic foraminifera record [55]. The section is predominantly
characterized by marls, except for the 10-cm K-Pg boundary clay layer (Figure 7) [59].
As with other sections, the K-Pg transition at Caravaca is accompanied by a drop in
percent carbonate, a negative excursion in the fine fractions of 813 C [59], and a decrease
in species richness [55]. Additionally, there are elevated concentrations of pyrosynthetic
polycyclic aromatic hydrocarbons (PAHs), indicative of burned biomass, within the first
0.5 cm of the boundary clay [60].
SPAIN
2030
-
Agost
SDhm
0
Mficante
10
Caravaca
Murcia
10
To Granada
TOCkkaa
ora
-1-
50km
Figure 6. Location of Caravaca within Spain. Figure
taken from Alegret et al., 2003 [61].
-30
Figure 7. Stratigraphy at
Caravaca (K-Pg is at 0 cm).
Figure taken from Kaiho et al.
(1999) [59].
28
In order to determine the average MAR in the Late Maastrichtian at Caravaca, we
combined magnetostratigraphy with astronomically calibrated cyclostratigraphy. The
base of C29r is reported to be 11.7 m below the K-Pg [59, 62], and the time in between
the start of C29r and the K-Pg is estimated to be 328.425 (±7.248) kyr based on the
preferred cyclostratigraphic tuning option presented by Westerhold et al. [63]. From
these values, we calculate an estimated Late Maastrichtian sedimentation rate of 3.56
(+0.08) cm kyr-1. We have estimated the density of all samples from this section to be
2.23 g cm-3 by averaging the measured densities for four samples of different heights
with varying carbonate content. These values were calculated by dividing the rock mass
by the volume measured when the rock was placed into a graduated cylinder partially
filled with water. Problems with density determination will be discussed below.
Multiplying the density by the sedimentation rate gives us an average Late Maastrichtian
MAR of 7.9x10 4 g m-2 kyr-1.
29
El Kef; Tunisia
The K-Pg section at El Kef in northwestern Tunisia (Figure 8) is not only one of
the most complete but also one of the most expanded sections due to the shallow
depositional depth and high sedimentation rates [56, 64]. As a result, El Kef has been
designated the Global Boundary Stratotype Section and Point (GSSP) for the K-Pg
transition by the International Commission on Stratigraphy (ICS) [64]. The section was
deposited in an outer neritic setting [58] near the Kasserine Island at an approximate
paleodepth of 200 m [56] and paleolatitude of 20'N [65]. The boundary clay is 50 cmthick and is bounded by Maastrichtian marl and Danian marly clay (Figure 9) [21].
ITrr
AOY
TUNIS
Z
I
I
Os*
Figure 9. Stratigraphy at El Kef (K-Pg is 0
A
cm). The hatched pattern denotes marl, the
horizontal stripes denote marly clay, and the
solid gray denotes clay. Figure from
Arenillas et al., 2002 [66].
Figure 8. Location of El Kef (starred)
within Tunisia. Figure modified after
Molina et al., 2006 [64].
30
Within the clay layer, there is a decrease in percent carbonate, maximum in TOC, and
negative excursion in
8 13 C
in the fine fraction of carbonate [67], and species turnover
[66].
The Late Maastrichtian sedimentation rate at El Kef was determined by matching
the Sr isotope record with the record at Bidart, France, where cyclostratigraphic data is
available, and it is estimated to be 8.5 cm kyr'1 [68]. As with Caravaca, we have assumed
the densities of all samples to be the same at 1.91 g cm-1 based on averaging measured
densities in 3 samples of varying stratigraphic height. From these estimates, we calculate
an estimated Late Maastrichtian MAR of 1.6x1 05 g m-2 kyr'.
31
Stevns Klint, Denmark
The Stevns Klint area in eastern Denmark consists of several kilometers of
seaside cliffs with well-exposed Cretaceous and Paleogene outcrops (Figure 10) [57].
Stevns Klint is well known for its Cretaceous coccolith chalk [57], and the darker
boundary clay, known as the Fish Clay, is conspicuous against the chalk background.
Several outcrops in this area have been studied, with Hojerup being the most common
[52, 57]. However, other seemingly more expanded sections exist, including
Kulstirenden, which is 8.5 km to the north of Hojerup [52]. In this study, we analyzed
samples from both Hojerup and Kulstirenden. The sections at Stevns Klint were
deposited at a paleolatitude of 48'N [13] in an inner shelf setting with a depth around
100-150 m, although there is evidence that shallowing occurred through the K-Pg [57].
These sections were located in the Danish Basin, which did not have a true continental
shelf [69].
The oldest exposed Maastrichtian sediments are flat-lying wackestones made of a
white, bryozoan-rich coccolith chalk matrix (Figure 12) [57]. This unit is truncated by
two incipient hardgrounds, which sit below the Grey Chalk. The Grey Chalk appears as
small mounds and contains more macrofossils than the white chalk below. At
Kulstirenden, the Grey Chalk is very thin and in some places nonexistent, but it appears
much thicker at Hojerup. Because of the mounds, the upper boundary of the Grey Chalk
undulates. The overlying Fish Clay is found in the troughs of the mounds, and, at the
crests, the Fish Clay occasionally disappears so that the overlying Cerithium Limestone is
directly on top of the Grey Chalk. As a result, the thickness of the Fish Clay varies
throughout the region. At some outcrops in Kulstirenden, the Fish Clay expands to be 37
32
cm-thick (Figure 11) [21], whereas at Hojerup, the thickness is around 5.5 cm. The K-Pg
in both sections is associated with a decrease in the percent carbonate [57], an increase in
TOC [21], decrease in
8 13 C
in the fine fraction of carbonate, and species turnover [57].
Based on carbon isotope stratigraphy and correlation with cyclostratigraphy [70,
71], I have estimated the Late Maastrichtian sedimentation rate at Kulstirenden to be 8.89
cm kyr~1. Assuming a density for all samples of 1.75 g cm-3, based on averaging
measured densities, we calculate a Late Maastrichtian MAR of 1.56x 05 g M-2 kyr 1 .
Owing to a lack of more accurate published estimates, we have used a Late Maastrichtian
sedimentation rate of 7 cm kyr-' for Hojerup, based on comparison between Danish
sections and an assumed maximum sedimentation rate [72]. Using the same densities as
for Kulstirenden, we have calculated a Late Maastrichtian MAR of 1.23x10 g M-2 kyr- 1.
Figure 10. Locations of
*,a.
Kulstirenden and
Basdv
"
Hojerup in Denmark
from Hart et al.,
2005 [57, 73].
Store
Heddinge
40
35
"
20
1s
10
s~ne
Figure 11.
Stratigraphy at-
,from
Sepdmlveda
at.yayeml
-taigah
etbal., [21]
33
m~a
.f,~
'1
'I
II
'I'
I'
scIrtigah
'~
'
'
l~
S
I.
\
'~
Wi0
I
I'
~
~
2'
I '.1:
I
/
\\
I.
IS
i
1/
I
1,
I
sa1I
B
I
&
.. ,
,~
'Fo
'N'
.0
j
1~
II
~h
*
~
a
II
In
~
1310J
0;5
isV
11W
J.La
V
bi
3
215K
Si
~
I.
u~
I
~
'I
*
j
II
ID
'S
~
~
imI
CM
oil
3
I%
V
ISOY
:
.
C
*
*
,
*1SI
I'
I
.:i
SI
I
I
I
I
I "I I
~~
to]II III l
fromu Har et a.,0053574
34
'
'I
II
1'~
~
~
b 19
~I
I
~
It is important to note that these are average estimates and that two incipient hardgrounds
exist near the top of the Cretaceous sediments, implying a hiatus [57]. Therefore, these
MAR estimates may not produce reliable 3 HeET flux values. Other problems with Stevns
Klint will be discussed below.
35
This page intentionally left blank.
36
Chapter 5: Results and Discussion
We used helium isotope measurements to calculate the flux of 3 HeET to the
sediments in each of the sections. From this, we determined instantaneous mass
accumulation rates, which allowed for the estimation of sedimentation rates and
accumulation rates of carbonate fractions, non-carbonate fractions, and sterane
biomarkers. A summary of the 3 HeET results is shown in Table 1-2. All sections have
comparable mean Maastrichtian
3HeET
concentrations and fluxes. Table 1 also shows the
minimum percent of 3 He that was extraterrestrial in origin within the entire sample set at
each section. The 3 He in the Danish sections is almost all extraterrestrial, while at
Caravaca and El Kef, the extraterrestrial percent ranges from ~34-85% and -14-57%,
respectively. For all sections, we have assumed constant density, therefore resulting in
identical trends in sedimentation rates and mass accumulation rates. In all figures below,
the gray shading signifies the boundary clay layer, and the K-Pg is located at a height of 0
cm.
37
Table 1. Comparison of 3HeET results from all sections.
Mean Maastrichtian
S3HeETI
(10-1 cc STP g )
ImpliedfHe
(10-" cc STP m-2 kyr~
Approximate Range
of Extraterrestrial
Percent Of He(%)
Caravaca
115.4 (±4.75)
91.7 (±3.8)
34-85
El Kef
117.8 (±9.92)
191.2 (±16.1)
14-57
Hojerup
303.5 (±30.4)
374.0 (±37.4)
95-98
Kulstirenden
173.3 (±11.7)
271.1 (±18.3)
93-97
38
Table 2. He concentrations and ratios for all samples in this study. Stratigraphic height is
relative to the K-Pg at Ocm.
Stratigraphic
Height (cm)
[3He]
(10-15 cc STP g-')
±1G
I4He]
(10~9 cc STP g-)
3
±lg
He/4He
(RA)
Caravaca
-850
-740
-680
-650
-580
-550
-500
-400
-350
-300
-200
-175
-125
-77.5
-52.5
-26.5
-16.5
-11
-2
1.25
2.5
3.5
4.5
5.5
6.5
8.5
9.5
12
15
17
20
13.7
15.8
13.3
11.0
14.4
17.7
15.7
24.8
18.9
10.9
14.9
13.5
11.4
12.8
11.8
11.9
19.9
41.4
72.2
68.9
81.3
68.1
75.2
36.5
38.7
38.9
51.1
104.5
34.9
51.1
71.7
1.9
1.6
1.9
1.6
2.0
2.5
2.2
3.5
2.7
1.5
2.1
1.9
1.6
1.8
1.7
1.7
2.8
5.9
8.3
8.0
9.4
7.9
7.5
4.2
5.5
5.5
7.2
12.1
4.9
7.2
8.3
139.3
126.3
145.2
139.4
186.4
265.2
324.6
169.2
221.7
149.3
141.2
110.9
151.1
116.2
126.4
114.7
112.6
429.8
347.6
1074.7
902.7
883.0
604.3
409.1
546.9
528.1
718.6
643.5
529.9
464.1
264.9
Table 2. (continued)
39
19.7
12.6
20.5
19.7
26.4
37.5
45.9
23.9
31.4
21.1
20.0
15.7
21.4
16.4
17.9
16.2
15.9
60.8
40.1
124.1
104.2
102.0
60.4
47.2
77.3
74.7
101.6
74.3
74.9
65.6
30.6
0.07
0.09
0.07
0.06
0.06
0.05
0.03
0.11
0.06
0.05
0.08
0.09
0.05
0.08
0.07
0.07
0.13
0.07
0.15
0.05
0.06
0.06
0.09
0.06
0.05
0.05
0.05
0.12
0.05
0.08
0.19
Stratigraphic
Height (cm)
El Kef
-540
-240
-10
0.5
5
10
20
70
100
120
[3 He]
(10-15 cc STP
3He/4He
[4He]
g-1)
(10-9 cc STP g-)
(RA)
28.3
22.9
24.7
30.6
24.9
28.0
25.3
33.3
25.4
26.0
4.0
3.2
3.5
4.3
5.0
4.0
3.6
4.7
3.6
3.7
336.3
366.4
270.0
317.3
291.5
350.9
344.1
359.6
388.7
342.8
47.6
51.8
38.2
44.9
58.3
49.6
48.7
50.9
55.0
48.5
0.06
0.04
0.07
0.07
0.06
0.06
0.05
0.07
0.05
0.05
31.9
30.7
132.3
130.8
165.6
162.2
130.8
76.2
4.5
4.3
15.3
15.1
19.1
22.9
18.5
10.8
23.0
22.4
112.9
143.0
202.6
157.2
123.4
28.4
3.2
3.2
13.0
16.5
23.4
22.2
17.4
4.0
1.00
0.98
0.84
0.66
0.59
0.74
0.76
1.93
29.9
11.6
13.0
276.4
219.3
237.3
205.2
219.5
191.7
11.8
18.4
3.0
1.6
1.3
39.1
31.0
33.6
29.0
31.0
38.3
1.7
2.1
23.5
13.2
21.9
398.4
356.3
327.4
274.4
303.8
243.7
13.7
13.6
2.4
1.9
2.2
56.3
50.4
46.3
38.8
43.0
48.7
1.9
1.6
0.91
0.63
0.43
0.50
0.44
0.52
0.54
0.52
0.57
0.62
0.98
Hojerup
-51
-10
1
2
3
5
6
8.25
Kulstirenden
-105
-6
-3
0.5
1.95
4.45
10.65
16.65
23.65
40
45
40
Caravaca,Spain
At Caravaca, there is an initial drop in the instantaneous sedimentation rate at the
K-Pg (Figure 13a). Within the first 5 cm of the boundary clay, the sedimentation rates
are generally lower than in the last 5 cm of the clay and are noticeably lower than the
Maastrichtian sedimentation rate. The sedimentation rate appears to increase in the
second half of the boundary clay although there is scatter. The sedimentation rates are
also scattered in the 5 cm above the boundary clay. Both the mass and carbonate
accumulation rates display trends similar to the sedimentation rate, suggesting that the
changes in deposition are dominantly driven by changes in carbonate burial (Figure 13c).
A decrease in carbonate burial is generally expected at the K-Pg due to the extinction of
many calcareous organisms, possibly as a result of transient ocean acidification [14]. The
non-carbonate accumulation rate shows a slow and subtle decrease from the K-Pg to the
youngest Danian sample, although there is no drastic change within the boundary clay.
This suggests that terrestrial input was roughly uniform through the mass extinction event.
Figure 13b shows that the upper half of the boundary clay was deposited slightly faster
than the lower half. We calculate that the 10-cm boundary clay was deposited in 6.45 (
0.86) kyr.
Within the boundary clay, there is scatter in the accumulation rates of C2 6-C 30
sterane biomarkers, which are proxies for algal productivity (Figure 14). The biomarker
data was provided by Dr. Julio Sepnllveda. However, there is a noticeable decrease from
the Maastrichtian to the Danian, which is expected for mass extinctions. Figure 15 shows
the carbonate fraction, '8 3 C (bulk carbonate), and
6180
(bulk carbonate) at Caravaca, also
provided by Dr. Julio Sepulveda. All three records show a decrease at the K-Pg with a
41
gradual recovery. The carbonate content returns to pre-boundary values within ~6 kyr,
and the
6180
values return to pre-boundary values within 5 kyr. The
return to pre-boundary values within our stratigraphic range.
42
8 13 C
values do not
Caravaca
a
b
25
100
-0-
U)
E 20
80
8
Z 15
060
X
10
-V
-0p
40
0
5
20
010
0
I
1
2
3
Sedimentation Rate (cm kyr')
0
C
25
-0--
0
4
0
2
4
6
Time Elapsed (kyr)
I
8
+ Total Mass
* Carbonate
SANon-carbonate
20
-0--4--
E
2-15
'C
A
U--4-
10
R~
______
'C
5
~
0
I
I
A
I
U
-5
0
1
2
3
4
5
6
2
Accumulation Rate (104 g m- kyr')
7
8
9
Figure 13. a) Instantaneous sedimentation rates of Danian samples at Caravaca with the
boundary clay shaded. Average Maastrichtian value is plotted at a height of 0 cm (no
error bars) for comparison. b) The percent of the boundary clay deposited at Caravaca
versus the time elapsed. c) The instantaneous accumulation rates of total mass, carbonate,
and non-carbonate portions at Caravaca.
43
25
20
p
15
E
0
10
0)
5
0
I
I
I
I
'U
-5
-10
0
-15
0
20
40
60
80
100
2
C26-C30 Sterane Accumulation Rate (mg m- kyr')
Figure 14. Accumulation rate of C26-C 30 steranes at Caravaca, indicative of algal
productivity.
44
120
20
15
+
-
-
110
I
it
~5
C.,'
0
f
+
T4
T-
--
S
0
0
0
-5
0
0.2
0.4
0.6
0.8
Carbonate Fraction
1
0
0.5
11
1.5
5 3C (%$)
2
2.5 -4
-3
-2
6130 (%0)
-1
3C (bulk carbonate), and 6180
Figure 15. Carbonate fraction, V'
(bulk carbonate) at Caravaca, where the K-Pg is
at 0 kyr.
0
El Kef Tunisia
The sedimentation rate at El Kef shows a possible short-lived decrease at the KPg, but within the lower half of the boundary clay, rates return to pre-extinction values
(Figure 16a). However, only samples from the lower portion of the boundary clay were
available for analysis, so the trends through the upper part of the clay are unknown.
Based on the samples analyzed, it is likely that the majority of the boundary clay was
uniformly deposited (Figure 16b), and the sedimentation rate does not vary by more than
a factor of 2. The instantaneous mass accumulation rates have large error and are
scattered with no clear trends other than a possible short-lived decrease at the boundary
(Figure 16c). The carbonate accumulation rate appears to decrease at the K-Pg and stay
constant through the boundary clay, with values recovering at some point in the overlying
layers. The non-carbonate accumulation rate increases in the first half of the boundary
clay, suggesting that terrestrial input might have increased after the extinction.
We calculate that the boundary clay was deposited in 6.28 (± 1.03) kyr. The C2 6C3 0 sterane accumulation rate appears to increase at the K-Pg, although the values are
scattered (Figure 17). Biomarker data was provided by Dr. Julio Sepulveda. Figure 18
shows the carbonate fraction, 8 13 C (bulk carbonate), and 6180 (bulk carbonate) records
for El Kef, also provided by Dr. Julio Sepulveda. All three records show a decrease at
the boundary. Only the
6180
record returns to pre-boundary values within the
stratigraphic range of our samples, and this return occurs within roughly 12 kyr.
46
El Kef
a
b
100
14U
120
00
-100
0D
60
80
p
C60
a
40
8
t ep
p
40
20
0
0
0
10
5
Sedimentation Rate (cm kyr')
0
0
15
2
4
8
6
Time Elapsed (kyr)
C
140
*Total Mass
*Carbonate
120
ANon-carbonate
p
100
E
0
2 80
0>
:a:
.
60
.2 40
U)
20
*
_
_
_
_
_
_
_
0
-20
0
5
10
15
20
Accumulation Rate (104 g M-2 kyr')
25
30
Figure 16. a) Instantaneous sedimentation rates of Danian samples at El Kef with the
boundary clay shaded. Average Maastrichtian value is plotted at a height of 0 cm (no
error bars) for comparison. b) The percent of the boundary clay deposited at El Kef
versus the time elapsed. c) The instantaneous accumulation rates of total mass, carbonate,
and non-carbonate portions at El Kef.
47
140
120
E
100
80
4-
60
40
20
-4----
0
-20
0
10000
30000
20000
40000
2
C2 6-C30 Sterane Accumulation Rate (mg m- kyr')
Figure 17. Accumulation rate of C26-C 30 steranes at El Kef, indicative of algal
productivity.
48
50000
20
+
15
'I
+f
.10
F
'1 5
+
&----------
A
0
-
- T
0
-5
0
0.1
0.2
0.3
0.4
Carbonate Fraction
Figure 18. Carbonate fraction,
where the K-Pg is at 0 kyr.
0.5
513 C
0.6 -2
-1
0
51C
1
)
2
-5
-4
(bulk carbonate), and 6180 (bulk carbonate) at El Kef,
-3
-
o )
-1
0
Hojerup, Denmark
The sedimentation and mass accumulation rates at Hojerup decrease significantly
at the K-Pg, stay roughly constant through the boundary clay, and rise slightly in the
overlying sediments (Figure 19a,c). However, the values don't recover within the range
of samples we analyzed. The carbonate accumulation rate drops even more drastically at
the boundary and increases through the boundary and overlying sediments to values
approaching the total mass accumulation rate. The non-carbonate accumulation rate
increases at the K-Pg and decreases through the boundary clay and overlying sediments
to pre-boundary values. The carbonate and non-carbonate accumulation rates have an
inverse relationship, and the results suggest terrestrial input increased at the boundary at
the same time that carbonate burial decreased. The boundary clay appears to have been
deposited at a uniform rate (Figure 19b). We have calculated that the 5.5-cm boundary
clay was deposited in 3.70 (± 0.71) kyr.
50
Hojerup
a
b
9
100
.8
0
E
80
2 7
.26
a
0
=5
60
0
4
0(3L3
-o
40
0
S2
20 i
0
01
0
IL
0
C
2
4
6
Sedimentation Rate (cm kyr')
8
0
0
2
4
Time Elapsed (kyr)
10
6
* Total Mass
A
no.
M
IN
U Carbonate
A Non-carbonate
0
*
5
-c
E,
0
0E
ca
-5
-10
-15
0
2
4
6
8
10
2
Accumulation Rate (104 g m- kyr')
12
14
Figure 19. a) Instantaneous sedimentation rates of Danian samples at Hojerup with the
boundary clay shaded. Average Maastrichtian value is plotted at a height of 0 cm (no
error bars) for comparison. b) The percent of the boundary clay deposited at Hojerup
versus the time elapsed. c) The instantaneous accumulation rates of total mass, carbonate,
and non-carbonate portions at Hojerup.
51
Kulstirenden,Denmark
Kulstirenden shows the most dramatic effects at the K-Pg in terms of sedimentary
changes. The sedimentation, mass accumulation, and carbonate accumulation rates all
decrease drastically at the boundary and stay depressed throughout the Fish Clay with
values recovering in the overlying Cerithium Limestone (Figure 20a,c). The noncarbonate accumulation rate stays low and constant throughout the range of our samples,
implying that carbonate burial is the controlling factor of the sediment accumulation at
Kulstirenden and that there is low terrestrial input. The boundary clay was deposited
roughly uniformly (Figure 20b). We calculate that the 37-cm boundary clay was
deposited in 41.54 (± 2.67) kyr. Figure 21 shows the carbonate fraction, 6 13 C (bulk
carbonate), and 6180 (bulk carbonate) records at Kulstirenden, provided by Dr. Julio
Sepulveda. The carbonate fraction decreases at the boundary and returns to pre-boundary
values within -42 kyr. The 613C values increase just above the K-Pg and quickly
approach the pre-boundary values within 15 kyr, never quite reaching them. The 6180
values initially decrease but subsequently increase and remain constant. Within -3 kyr,
the record steadies out at a value slightly higher than pre-boundary values.
52
Kulstirenden
b
a 50
.-- 45
E
B40
S35
Z 30
* 25
20
.
p
*I
~
C.
80
L
60
-o
40
~
4
.15
0
20
S10
5
0
0
0
C
""
100
op
5
10
15
Sedimentation Rate (cm kyr')
+
0
0
0
20
20
40
Time Elapsed (kyr)
60
50
-U
-
40
+*Total Mass
E
2- 30
OCarbonate
ANon-carbonate
.2 20
0
U0
M
A
-10
0
5
10
15
20
2
Accumulation Rate (104 g m- kyr')
25
30
Figure 20. a) Instantaneous sedimentation rates of Danian samples at Kulstirenden with
the boundary clay shaded. Average Maastrichtian value is plotted at a height of 0 cm (no
error bars) for comparison. b) The percent of the boundary clay deposited at
Kulstirenden versus the time elapsed. c) The instantaneous accumulation rates of total
mass, carbonate, and non-carbonate portions at Kulstirenden.
53
50
45
40
35
S30
25
20
15
10
I.
5
a
0
0.2
-5
0.4
0.6
0.8
1 0.5
C-Fraction
Figure 21. Carbonate fraction, 5 13C (bulk carbonate), and
Kulstirenden, where the K-Pg is at 0 kyr.
1I
1.5
513C (%.)
6180
(bulk carbonate) at
2 -2.5
-2
-1.5
-1
813 (%.)
-0.5
0
The Caravaca data set contains the most samples, and we are confident in the
estimatedfHe because of the number and height distribution of the Maastrichtian samples.
The boundary clay is also well sampled, allowing us to see trends. The other three
sections only have a few Maastrichtian background samples, and so we are less confident
infHe estimates. Regardless of our estimates forfHe, which are constant at each site, the
relative trends in accumulation rates would remain the same at each of the sections, and
only the absolute rates would change.
Given the data we have, El Kef shows the least amount of changes in
sedimentation, evidenced by the negligible changes in MAR from the Maastrichtian to
the boundary clay (Figure 16c, Table 4). However, we lacked samples from the upper
half of the boundary clay at El Kef, making it difficult to form conclusions about the
trends. More apparent changes in sedimentation are seen at Caravaca, though they are
not as drastic as the changes at Hojerup and Kulstirenden. El Kef has the highest amount
of terrigenous influx with a non-carbonate accumulation rate an order of magnitude
greater than the other three sections. There is only a small drop in the carbonate
accumulation rate at El Kef, and despite the lower percent of carbonate, the carbonate
accumulation rates in the boundary clay at El Kef are still comparable if not higher than
at the other sections. The high terrigenous influx is a result of the paleogeography of the
section, which was deposited on a continental shelf proximal to the Kasserine Island [56].
The island presumably was the source of the non-carbonate sediment found in this
section. El Kef may have had higher terrigenous input than the other three sections
because its location was closer to the continent; Caravaca had a deeper paleodepth, and
55
the Stevns Klint sections, though shallow, were part of a continental basin and may have
been far from the continent.
Caravaca shows changes at the K-Pg that are more obvious than changes at El Kef,
but they are not as drastic as at Stevns Klint (Figure 13c, Table 4). Caravaca had a
smaller amount of carbonate accumulation within the boundary clay compared with El
Kef but more than at either of the Danish sections, which suggests that the mass
extinction of calcareous organisms was most disastrous at Stevns Klint followed by
Caravaca and El Kef. Caravaca has lower non-carbonate accumulation rates than El Kef
because the section was deposited farther from the continent and at a lower depth.
The two sections at Stevns Klint show the most severe changes in sedimentation
with large decreases in the mass and carbonate accumulation rates, although changes at
Hojerup are less extreme than at Kulstirenden (Figures 19c, 20c; Table 4). Though
Hojerup and Kulstirenden are part of the same depositional system, they show different
trends in the carbonate and non-carbonate accumulation rates. At Hojerup, the carbonate
and non-carbonate accumulation rates have inverse trends, with the non-carbonate
accumulation rate decreasing gradually and the carbonate increasing. At Kulstirenden,
the non-carbonate fraction is low and constant throughout, and the carbonate fraction
drops and remains depressed through the boundary clay. Low terrigenous input is
expected because of the arid climate and lack of continental margins in the Danish Basin
[69]. Additionally, these sections may have been deposited far from the continent.
The depositional environment of Stevns Klint is unique, and stratigraphy varies
among different sections. The Fish Clay at Stevns Klint was deposited on the Grey Chalk
56
layer, which is composed of mounds [57]. The upper boundary of the Grey Chalk
undulates through the region, and the Fish Clay was deposited in its troughs. Therefore,
some outcrops have expanded boundary clay sections, and in others, the Fish Clay thins
out. The Grey Chalk likely formed in a manner similar to that of the older Maastrichtian
chalk mounds lower in the section [69]. These mounds are thought to have been made
from migrating mounds formed by biological and physical processes. The complexity in
the mechanics of deposition at Stevns Klint makes it difficult to calculate sedimentation
rates, which have lateral variations as we have seen in the differences between Hojerup
and Stevns Klint. We suspect that during the deposition of the Fish Clay, sediment
focusing occurred in the troughs of the Grey Chalk. Therefore, the highest sedimentation
rates of the Fish Clay would be found above sections of the Grey Chalk with the lowest
sedimentation rates, as the mound crests grew at a faster rate [69]. This leads us to
believe that the [3HeET] flux estimates in Danish Maastrichtian sections are not the same
as for the overlying Danian sediments. Therefore, we conclude that the sections at Stevns
Klint are not suitable for a high-resolution study using 3 HeET and that our absolute
boundary clay age estimates are incorrect. The estimates of sedimentation and mass
accumulations rates in the Maastrichtian and boundary clay layer are shown in Table 4.
The estimated durations of boundary clay deposition at all four sections are
summarized in Table 3. The estimates for both Caravaca and El Kef are on the same
order of magnitude as those from other studies. Mukhopadhyay et al. (2001) used the
3
HeET constant flux proxy to infer mass accumulation rates at the K-Pg and estimated the
duration of boundary clay deposition to be 7.9 (+1.0) kyr at Gubbio, Italy; 10.9 (±1.6) kyr
at Monte Conero, Italy; and 11.3 (+2.3) kyr at Ain Settara, Tunisia [23]. Based on the
57
sedimentation rate estimates of Arinobu et al. (1999), the sedimentation rate of the
boundary clay at Caravaca is 0.8 cm kyr-1, and the duration is 12.5 kyr, which is twice
our value [60]. Based on estimates of Arenillas et al. (2002), the sedimentation rate of
the boundary clay at El Kef is 10.7 cm kyr-1, and the duration is 4.7 kyr. This agreement
supports the notion of a cosmopolitan boundary clay layer that was deposited during the
same interval worldwide. Hojerup has a smaller duration estimate, while Kulstirenden
has an estimated duration that is an order of magnitude larger than the others. As stated
above, we assume that these values are not valid estimates given the complicated and
heterogeneous sedimentation at Stevns Klint.
Since carbonate accumulation rates reflect changes in carbonate burial and are
correlated to calcareous productivity, we cannot evaluate the effects of the mass
extinction on non-calcareous organisms from the carbonate record. Therefore, we
calculated accumulation rates of C26-C3 0 sterane biomarkers at Caravaca and El Kef.
This record reflects the productivity of both calcareous and non-calcareous algae, and we
observe different trends at each site. Accumulation rates at Caravaca are scattered and
possibly decrease at the K-Pg while those at El Kef increase. However, with
Maastrichtian biomarkers measured in only two samples at Caravaca and one at El Kef, it
is difficult to be sure of the trends. The decrease at Caravaca may be due to the
extinction of calcareous algae that had contributed to the sterane records. Because El Kef
suffered a less severe decrease in the carbonate accumulation rate than did Caravaca, we
might expect to see a smaller decrease in the accumulation rate of algal biomarkers.
However, we see an increase at El Kef on a scale three orders of magnitudes larger than
the scale at Caravaca. Therefore, another factor separate from the extinction of
58
calcareous organisms must have contributed to the change in sterane accumulation rates
and inferred changes in algal productivity. The increase in the sterane biomarker
accumulation rate at El Kef could be consistent with the increase in non-carbonate
accumulation rate observed if a portion of the steranes is terrestrial in origin. It is
possible that the increase in sterane accumulation rates at El Kef may be related to the
increase in the non-carbonate fraction. Perhaps increased weathering as a result of acid
rain or sea level change prompted algal blooms. However, there is also evidence of
increased terrestrial input at Caravaca seen in the fatty acid biomarker records [74], and
using the same reasoning as with El Kef, we would expect an increase in sterane
biomarkers. Therefore, we cannot explain the differences in these records.
In this study, we have made several assumptions, which were presented above.
We assumed constant values for the sedimentation and mass accumulation rates at the
end of the Maastrichtian. We assumed a constant density for all samples and may have
overestimated the value due to the method we used to calculate it. We measured the
volume change when a rock was placed in a graduated cylinder partially filled with water.
Though the volume was recorded as quickly as possible after the rock was added, it is
likely that some water filled the pore spaces in the rock, resulting in an underestimate of
rock volume and overestimate of density. However, this overestimation does not affect
the timescale calculation. Rearranging and combining Equations 1-2 after applying them
to the Cretaceous and Paleogene produces the following equation:
59
SRp =p. SRK' 3 [
g
p_[
Equation 5
3
HeETK)
HeET] I
where SRpg is the instantaneous sedimentation rate for a given sample (cm kyr-),
SRK is the average sedimentation rate for the Maastrichtian (cm kyr-1),
p is the in situ sediment density for all samples at a given section (g cc-'),
3
[3 HeETK] is the mean Maastrichtian concentration of HeET (c STP g-),
1
3
3
[ HeET] is the concentration of HeET for a given sample (cc STP g- )
p cancels out, implying that our choice of density does not affect calculated Paleogene
timescales. Density estimates only affect the Maastrichtian and Danian MARs.
We chose helium isotope ratios of 0.03 RA and 290 RA for the terrigenous and
extraterrestrial end-members, which have yielded a low percent of extraterrestrial
contribution. The end-member values affect the absolute timescales and sedimentation
rates but do not affect the relative trends in sedimentation rate. Changing 3 He/ 4 He of the
extraterrestrial end-member to 190 RA resulted in a nearly imperceptible change in the
fraction of 3He that is extraterrestrial and does not change our results. However, the
calculated extraterrestrial fraction of 3He is greatly affected by the choice of 3 He/ 4 He of
the terrestrial end-member.
When we changed the terrestrial helium isotope ratio to a lower bound of 0.01
and kept the extraterrestrial value at 290
RA,
RA
the fraction of extraterrestrial 3He increased
drastically at Caravaca (minimum 71%) and El Kef (minimum 77%), which have lower
3
He/4He ratios than the Danish sections and are therefore more sensitive to the choice of
the terrigenous end-member. Decreasing the terrestrial end-member helium isotope ratio
increases the Danian timescales, and the greatest change is seen at Caravaca where the
boundary clay interval increases by ~1.4 kyr to 7.9 kyr. The magnitude of the changes at
other sections are smaller. When the terrigenous end-member ratio was increased to
0.0348 RA and the extraterrestrial end-member kept at 290 RA, the extraterrestrial
60
component of 3 He and the Danian timescales decrease. The most significant change is
also seen at Caravaca, where the interval of boundary clay deposition decreases by -550
yr to 5.9 kyr. The of 0.0348
RA
as an upper bound for the terrigenous end-member was
based on the lowest 3He/ 4He value for our entire data set, which belongs to a
Maastrichtian sample at Caravaca. 0.01
RA
and 0.0348
RA
are both extreme estimates for
the terrestrial end-member, and their effects do not change the order of magnitude of the
results. Therefore, we are comfortable using our relatively conservative value of 0.03
RA
for the terrigenous end-member despite the low contributions of extraterrestrial He.
Another choice we made was to calculate carbonate and non-carbonate
accumulation rates using the carbonate fraction measured by other researchers. We
decided to use their values as opposed to the values we measured after acetic acid
treatment because our method was not as accurate. Acetic acid does not remove
carbonate as thoroughly as does HCl, and with our method, samples were dried in an
oven after acid treatment for less than 24 hrs. Therefore, we cannot be completely sure
that all water was removed, and this might have produced slightly higher end weights and
lower carbonate fractions. In order to see if the choice of carbonate fraction
determination affected our results, we used the values calculated in this study to calculate
alternative carbonate and non-carbonate accumulation rates. The results are very similar
to those presented above. The trends are generally the same, and, therefore, we conclude
that while absolute carbonate and non-carbonate accumulation rates may change with the
method of carbonate fraction determination, the relative changes in carbonate and noncarbonate accumulation rates are not very different. We feel confident with the carbonate
data we have used and presented.
61
Table 3. Comparison of boundary clay thickness and duration of boundary
clay deposition.
Thickness of
Duration of Boundary
Boundary Clay (cm)
Clay Deposition (kyr)
Caravaca
10
6.45 (L0.86)
El Kef
50
6.28 ( 1.03)
Hojerup
5.5
3.70(
Kulstirenden
37
0.71)
41.54 ( 2.67)
62
Table 4. Average sedimentation and mass accumulation rates in the
Maastrichtian and boundary c lay layers.
Ave age Boundary Clay
Sedimentation Rate (em
Average Boundary Clay
Mass Accumulation Rate
kyr )
(104 g m-2 kyrt)
7.94
1.55 (*0.21)
3.46 (*0.46)
8.5
16.24
7.96 (*1.30)
15.20 (*2.48)
Hojerup
7
12.32
1.49 (+0.29)
2.62 (A0.50)
Kulstirenden
8.89
15.65
0.89 (*0.06)
1.57 (A0.10)
Maas
ge
Sedimentation Rate
Sedieti(om kyr
a)
Average Maastrlchtian
Mass Accumulation Rate
Caravaca
3.56
El Kef
(10' g in
2
kyrI)
This page intentionally left blank.
64
Conclusion
In this study, we used extraterrestrial helium-3 as a constant flux proxy for
instantaneous mass accumulations rates at four Cretaceous-Paleogene sections: Caravaca,
Spain; El Kef, Tunisia; and Hojerup and Kulstirenden, Denmark. We found that though
the He isotope ratios at Hojerup and Kulstirenden are favorable for this proxy, the
stratigraphy at the sections is not uniform. Sediment focusing of the Fish Clay in the
troughs of the Grey Chalk mounds resulted in variable 3 HeET fluxes to each layer, and we
cannot determine how the flux changed.
Our estimates at Caravaca and El Kef agree with published boundary clay
estimates, and this supports a global deposition of the boundary clay within the same
interval. Carbonate accumulation rates show that Kulstirenden and Hojerup were the
most affected by the mass extinction followed by Caravaca and El Kef. However,
carbonate accumulation reflects burial and not necessarily calcareous productivity. In
order to evaluate the productivity of both calcareous and non-calcareous algae, we
calculated accumulation rates of C2 6-C 30 steranes at Caravaca and El Kef. The El Kef
results show an increase in the algal sterane accumulation rate at the boundary, and this
may correlate with the increase in the non-carbonate fraction, suggesting an increase in
terrestrial input. However, there is scatter and a possible decrease at Caravaca, where we
also expected to see evidence for increased terrestrial input. At this time, we cannot
explain the different trends in biomarker accumulation rates at Caravaca and El Kef. A
higher-resolution and more comprehensive biomarker study at all sections would
complement this work.
65
It appears as though the severity of carbonate reduction increases with
paleolatitude, and if we assume that carbonate burial does reflect calcareous productivity,
then the calcareous extinction was more drastic at higher paleolatitudes. We do not have
enough information to draw conclusions about the effects of paleodepth on extinctions
and recovery because these sections have unique depositional environments. Hojerup
and Kulstirenden were located in the Danish Basin, and perhaps being located in this
constricted body of water exacerbated the mass extinction. There is evidence for regional
acidification in other locations, and this may have occurred in the Danish Basin [14].
The effects would have been worse than acidification at sections like Caravaca and El
Kef where the ocean was not constricted.
Further geochemical and biogeochemical studies at higher resolution will improve
this work and our understanding of how different paleoenvironments responded to the KPg mass extinction event. Extending our sample sets to larger stratigraphic heights at
greater resolution will provide a high-resolution timescale that captures marine recovery
and the recovery to pre-boundary values in the records of carbonate accumulation and
isotopes. Additionally, we can calculate accumulation rates of biomarkers and
microfossils to better understand biological changes in the oceans. Though there is much
work to be done, this study is one small step in the right direction.
66
References
1.
Raup, D.M., and Sepkoski, J.J. (1982). Mass Extinctions in the Marine Fossil
Record. Science 215, 1501-1503.
2.
Gradstein, F.M. (2012). The geologic time scale 2012, 1st Edition, (Amsterdam;
Boston: Elsevier).
3.
Renne, P.R., Deino, A.L., Hilgen, F.J., Kuiper, K.F., Mark, D.F., Mitchell, W.S.,
4.
Morgan, L.E., Mundil, R., and Smit, J. (2013). Time Scales of Critical Events
Around the Cretaceous-Paleogene Boundary. Science 339, 684-687.
Schulte, P., Alegret, L., Arenillas, I., Arz, J.A., Barton, P.J., Bown, P.R.,
Bralower, T.J., Christeson, G.L., Claeys, P., Cockell, C.S., et al. (2010). The
Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene
Boundary. Science 327, 1214-1218.
5.
Pospichal, J.J. (1996). Calcareous nannoplankton mass extinction at the
Cretaceous/Tertiary boundary: an update. The Cretaceous,AiTertiary Event and
Other Catastrophes in Earth History: Geological Society of America Special
Paper 307, 335-360.
6.
7.
Keller, G. (1988). Extinction, Survivorship and Evolution of Planktic
Foraminifera across the Cretaceous Tertiary Boundary at El-Kef, Tunisia. Mar
Micropaleontol 13, 239-263.
Sheehan, P.M., Fastovsky, D.E., Hoffmann, R.G., Berghaus, C.B., and Gabriel,
D.L. (1991). Sudden Extinction of the Dinosaurs - Latest Cretaceous, Upper
8.
Great-Plains, USA. Science 254, 835-839.
Hildebrand, A.R., Penfield, G.T., Kring, D.A., Pilkington, M., Camargo, A.,
Jacobsen, S.B., and Boynton, W.V. (1991). Chicxulub Crater - a Possible
Cretaceous Tertiary Boundary Impact Crater on the Yucatan Peninsula, Mexico.
Geology 19, 867-871.
9.
10.
Alvarez, L.W., Alvarez, W., Asaro, F., and Michel, H.V. (1980). Extraterrestrial
Cause for the Cretaceous-Tertiary Extinction - Experimental Results and
Theoretical Interpretation. Science 208, 1095-1108.
Li, L.Q., and Keller, G. (1998). Abrupt deep-sea warming at the end of the
Cretaceous. Geology 26, 995-998.
11.
12.
Pope, K.O., Baines, K.H., Ocampo, A.C., and Ivanov, B.A. (1994). Impact Winter
and the Cretaceous-Tertiary Extinctions - Results of a Chicxulub Asteroid Impact
Model. Earth Planet Sc Lett 128, 719-725.
Bambach, R.K., Knoll, A.H., and Wang, S.C. (2004). Origination, extinction, and
mass depletions of marine diversity. Paleobiology 30, 522-542.
13.
Aberhan, M., Weidemeyer, S., Kiessling, W., Scasso, R.A., and Medina, F.A.
(2007). Faunal evidence for reduced productivity and uncoordinated recovery in
Southern Hemisphere Cretaceous-Paleogene boundary sections. Geology 35, 227-
230.
14.
15.
Alegret, L., Thomas, E., and Lohmann, K.C. (2012). End-Cretaceous marine mass
extinction not caused by productivity collapse. P Natl Acad Sci USA 109, 728-
732.
Wolbach, W.S., Gilmour, I., Anders, E., Orth, C.J., and Brooks, R.R. (1988).
Global Fire at the Cretaceous Tertiary Boundary. Nature 334, 665-669.
67
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
Wolbach, W.S., Lewis, R.S., and Anders, E. (1985). Cretaceous Extinctions Evidence for Wildfires and Search for Meteoritic Material. Science 230, 167-170.
Prinn, R.G., and Fegley, B. (1987). Bolide Impacts, Acid-Rain, and Biospheric
Traumas at the Cretaceous-Tertiary Boundary. Earth Planet Sc Lett 83, 1-15.
Crutzen, P.J. (1987). Mass Extinctions - Acid-Rain at the K/T Boundary. Nature
330, 108-109.
Kring, D.A. (2007). The Chicxulub impact event and its environmental
consequences at the Cretaceous-Tertiary boundary. Palaeogeogr Palaeocl 255, 421.
D'hondt, S. (1998). Organic carbon fluxes and ecological recovery from the
Cretaceous-Tertiary mass extinction (vol 282, pg 276, 1998). Science 282, 105 11051.
Sepulveda, J., Wendler, J.E., Summons, R.E., and Hinrichs, K.U. (2009). Rapid
Resurgence of Marine Productivity After the Cretaceous-Paleogene Mass
Extinction. Science 326, 129-132.
Hull, P.M., and Norris, R.D. (2011). Diverse patterns of ocean export productivity
change across the Cretaceous-Paleogene boundary: New insights from biogenic
barium. Paleoceanography 26.
Mukhopadhyay, S., Farley, K.A., and Montanari, A. (2001). A short duration of
the Cretaceous-Tertiary boundary event: Evidence from extraterrestrial helium-3.
Science 291, 1952-1955.
Goldschmidt, V.M. (1954). Geochemistry, (Oxford,: Clarendon Press).
Barker, J.L., and Anders, E. (1968). Accretion Rate of Cosmic Matter from
Iridium and Osmium Contents of Deep-Sea Sediments. Geochim Cosmochim Ac
32, 627-&.
Farley, K.A. (1995). Cenozoic Variations in the Flux of Interplanetary Dust
Recorded by He-3 in a Deep-Sea Sediment. Nature 376, 153-156.
Mcgee, D., Marcantonio, F., McManus, J.F., and Winckler, G. (2010). The
response of excess Th-230 and extraterrestrial He-3 to sediment redistribution at
the Blake Ridge, western North Atlantic. Earth Planet Sc Lett 299, 138-149.
Ozima, M., Takayanagi, M., Zashu, S., and Amari, S. (1984). High He-3-He-4
Ratio in Ocean Sediments. Nature 311, 448-450.
Love, S.G., and Brownlee, D.E. (1993). A Direct Measurement of the Terrestrial
Mass Accretion Rate of Cosmic Dust. Science 262, 550-553.
Brownlee, D.E. (1985). Cosmic Dust - Collection and Research. Annu Rev Earth
P1 Sc 13, 147-173.
Burns, J.A., Lamy, P.L., and Soter, S. (1979). Radiation Forces on Small Particles
in the Solar-System. Icarus 40, 1-48.
McGee, D., and Mukhopadhyay, S. (2013). Extraterrestrial He in Sediments:
From Recorder of Asteroid Collisions to Timekeeper of Global Environmental
Changes. In The Noble Gases as Geochemical Tracers, P. Burnard, ed. (Springer
Berlin Heidelberg), pp. 155-176.
Merrihue, C. (1964). Rare Gas Evidence for Cosmic Dust in Modern Pacific Red
Clay. Ann Ny Acad Sci 119, 351-&.
68
34.
Wieler, R., Baur, H., and Signer, P. (1986). Noble-Gases from Solar Energetic
Particles Revealed by Closed System Stepwise Etching of Lunar Soil Minerals.
Geochim Cosmochim Ac 50, 1997-2017.
35.
36.
Nier, A.O., and Schlutter, D.J. (1992). Extraction of Helium from Individual
Interplanetary Dust Particles by Step-Heating. Meteoritics 27, 166-173.
Marcantonio, F., Higgins, S., Anderson, R.F., Stute, M., Schlosser, P., and
Rasbury, E.T. (1998). Terrigenous helium in deep-sea sediments. Geochim
Cosmochim Ac 62, 1535-1543.
37.
38.
Farley, K.A., Love, S.G., and Patterson, D.B. (1997). Atmospheric entry heating
and helium retentivity of interplanetary dust particles. Geochim Cosmochim Ac
61, 2309-2316.
Mukhopadhyay, S., and Farley, K.A. (2006). New insights into the carrier
phase(s) of extraterrestrial (3)He in geologically old sediments. Geochim
Cosmochim Ac 70, 5061-5073.
39.
Stuart, F.M., Harrop, P.J., Knott, S., and Turner, G. (1999). Laser extraction of
helium isotopes from Antarctic micrometeorites: Source of He and implications
for the flux of extraterrestrial (3)He to earth. Geochim Cosmochim Ac 63, 2653-
40.
Patterson, D.B., Farley, K.A., and Schmitz, B. (1998). Preservation of
extraterrestrial He-3 in 480-Ma-old marine limestones. Earth Planet Sc Lett 163,
2665.
41.
42.
43.
44.
315-325.
Takayanagi, M., and Ozima, M. (1987). Temporal Variation of He-3/He-4 Ratio
Recorded in Deep-Sea Sediment Cores. J Geophys Res-Solid 92, 12531-12538.
Marcantonio, F., Anderson, R.F., Stute, M., Kumar, N., Schlosser, P., and Mix, A.
(1996). Extraterrestrial He-3 as a tracer of marine sediment transport and
accumulation. Nature 383, 705-707.
Marcantonio, F., Kumar, N., Stute, M., Anderson, R.F., Seidl, M.A., Schlosser, P.,
and Mix, A. (1995). Comparative-Study of Accumulation Rates Derived by He
and Th Isotope Analysis of Marine-Sediments. Earth Planet Sc Lett 133, 549-555.
Mukhopadhyay, S., Farley, K.A., and Montanari, A. (2001). A 35 Myr record of
helium in pelagic limestones from Italy: Implications for interplanetary dust
accretion from the early Maastrichtian to the middle Eocene. Geochim
Cosmochim Ac 65, 653-669.
45.
Farley, K. (2001). Extraterrestrial Helium in Seafloor Sediments: Identification,
Characteristics, and Accretion Rate Over Geologic Time. In Accretion of
Extraterrestrial Matter Throughout Earth,As History, B. Peucker-Ehrenbrink and
B. Schmitz, eds. (Springer US), pp. 179-204.
46.
47.
Fukumoto, H., Nagao, K., and Matsuda, J.I. (1986). Noble-Gas Studies on the
Host Phase of High He-3/He-4 Ratios in Deep-Sea Sediments. Geochim
Cosmochim Ac 50, 2245-2253.
Andrews, J.N. (1985). The Isotopic Composition of Radiogenic Helium and Its
Use to Study Groundwater Movement in Confined Aquifers. Chem Geol 49, 339-
48.
351.
Geiss, J., BTohler, F., Cerutti, H., Eberhardt, P., and Filleux, C. (1972). Apollo
16 preliminary science report. NASA SP-315 14, 1-14.
69
49.
Nier, A.O., and Schlutter, D.J. (1990). Helium and Neon Isotopes in Stratospheric
50.
Particles. Meteoritics 25, 263-267.
Winckler, G., Anderson, R.F., Fleisher, M.Q., Mcgee, D., and Mahowald, N.
51.
52.
(2008). Covariant glacial-interglacial dust fluxes in the equatorial Pacific and
Antarctica. Science 320, 93-96.
Farley, K.A., and Eltgroth, S.F. (2003). An alternative age model for the
Paleocene-Eocene thermal maximum using extraterrestrial He-3. Earth Planet Sc
Lett 208, 135-148.
Surlyk, F., Damholt, T., and Bjerager, M. (2006). Stevns Klint, Denmark:
53.
Uppermost Maastrichtian chalk, Cretaceous-Tertiary boundary, and lower Danian
bryozoan mound complex. B Geol Soc Denmark 54, 1-+.
Parai, R., Mukhopadhyay, S., and Lassiter, J.C. (2009). New constraints on the
HIMU mantle from neon and helium isotopic compositions of basalts from the
Cook-Austral Islands. Earth Planet Sc Lett 277, 253-261.
54.
55.
Scotese, C. PALEOMAP Project.
Coccioni, R., and Galeotti, S. (1994). K-T Boundary Extinction - Geologically
Instantaneous or Gradual Event - Evidence from Deep-Sea Benthic Foraminifera.
56.
Geology 22, 779-782.
Guasti, E., Kouwenhoven, T.J., Brinkhuis, H., and Speijer, R.P. (2005). Paleocene
sea-level and productivity changes at the southern Tethyan margin (El Kef,
Tunisia). Mar Micropaleontol 55, 1-17.
57.
Hart, M.B., Feist, S.E., Hakansson, E., Heinberg, C., Price, G.D., Leng, M.J., and
Watkinson, M.P. (2005). The Cretaceous-Palaeogene boundary succession at
Stevns Klint, Denmark: Foraminifers and stable isotope stratigraphy. Palaeogeogr
Palaeocl 224, 6-26.
58.
Canudo, J.I., Keller, G., and Molina, E. (1991). Cretaceous Tertiary Boundary
Extinction Pattern and Faunal Turnover at Agost and Caravaca, Se Spain. Mar
Micropaleontol 17, 319-341.
59.
Kaiho, K., Kajiwara, Y., Tazaki, K., Ueshima, M., Takeda, N., Kawahata, H.,
Arinobu, T., Ishiwatari, R., Hirai, A., and Lamolda, M.A. (1999). Oceanic
primary productivity and dissolved oxygen levels at the Cretaceous/Tertiary
boundary: Their decrease, subsequent warming, and recovery. Paleoceanography
60.
61.
62.
63.
14, 511-524.
Arinobu, T., Ishiwatari, R., Kaiho, K., and Lamolda, M.A. (1999). Spike of
pyrosynthetic polycyclic aromatic hydrocarbons associated with an abrupt
decrease in delta C- 13 of a terrestrial biomarker at the Cretaceous-Tertiary
boundary at Caravaca, Spain. Geology 27, 723-726.
Alegret, L., Molina, E., and Thomas, E. (2003). Benthic foraminiferal turnover
across the Cretaceous/Paleogene boundary at Agost (southeastern Spain):
paleoenvironmental inferences. Mar Micropaleontol 48, 251-279.
Smit, J. (1982). Extinction and evolution of planktonic foraminifera after a major
impact at the Cretaceous/Tertiary boundary, Volume 190, (Geological Society of
America).
Westerhold, T., Rohl, U., Raffi, I., Fornaciari, E., Monechi, S., Reale, V., Bowles,
J., and Evans, H.F. (2008). Astronomical calibration of the Paleocene time.
Palaeogeogr Palaeocl 257, 377-403.
70
64.
Molina, E., Alegret, L., Arenillas, I., Arz, J.A., Gallala, N., Hardenbol, J., von
Salis, K., Steurbaut, E., Vandenberghe, N., and Zaghbib-Turki, D. (2006). The
Global Boundary Stratotype Section and Point for the base of the Danian Stage
(Paleocene, Paleogene, "Tertiary", Cenozoic) at El Kef, Tunisia - Original
definition and revision. Episodes 29, 263-273.
65.
Petrizzo, M.R. (2003). Late cretaceous planktonic foraminiferal bioevents in the
tethys and in the southern ocean record: An overview. J Foramin Res 33, 330-337.
66.
Arenillas, I., Alegret, L., Arz, J.A., Liesa, C., Melendez, A., Molina, E., Soria,
A.R., Cedillo-Pardo, E., Grajales-Nishimura, J.M., and Rosales-Dominguez, C.
(2002). Cretaceous-Tertiary boundary planktic foraminiferal mass extinction and
biochronology at La Ceiba and Bochil, Mexico, and El Kef, Tunisia. Geol S Am S,
67.
253-264.
Keller, G., and Lindinger, M. (1989). Stable Isotope, Toc and Caco3 Record
across the Cretaceous Tertiary Boundary at El-Kef, Tunisia. Palaeogeogr Palaeocl
73, 243-265.
68.
69.
Vonhof, H.B., and Smit, J. (1997). High-resolution late Maastrichtian early
Danian oceanic Sr-87/Sr-86 record: Implications for Cretaceous-Tertiary
boundary events. Geology 25, 347-350.
Anderskouv, K., Damholt, T., and Surlyk, F. (2007). Late Maastrichtian chalk
mounds, Stevns Klint, Denmark - Combined physical and biogenic structures.
Sediment Geol 200, 57-72.
70.
Thibault, N., Husson, D., Harlou, R., Gardin, S., Galbrun, B., Huret, E., and
Minoletti, F. (2012). Astronomical calibration of upper Campanian-Maastrichtian
carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean
(ODP Hole 762C): Implication for the age of the Campanian-Maastrichtian
boundary. Palaeogeogr Palaeocl 337, 52-71.
71.
Thibault, N., Harlou, R., Schovsbo, N., Schioler, P., Minoletti, F., Galbrun, B.,
Lauridsen, B.W., Sheldon, E., Stemmerik, L., and Surlyk, F. (2012). Upper
72.
73.
Campanian-Maastrichtian nannofossil biostratigraphy and high-resolution carbonisotope stratigraphy of the Danish Basin: Towards a standard delta C- 13 curve for
the Boreal Realm. Cretaceous Res 33, 72-90.
Hansen, H.J.6., Rasmussen, K.L., Gwozdz, R., and Kunzendorf, H. (1987).
Iridium-bearing carbon black at the Cretaceous-Tertiary boundary. Bull. Geol.
Soc. Denmark 36, 305-314.
Hart, M.B., Feist, S.E., Price, G.D., and Leng, M.J. (2004). Reappraisal of the KT boundary succession at Stevns Klint, Denmark. J Geol Soc London 161, 885-
74.
892.
Arinobu, T., Ishiwatari, R., Kaiho, K., Lamolda, M.A., and Seno, H. (2005).
Abrupt and massive influx of terrestrial biomarkers into the marine environment
at the Cretaceous-Tertiary boundary, Caravaca, Spain. Palaeogeogr Palaeocl 224,
108-116.
71
This page intentionally left blank.
72
Table 5. Carbonate fraction, sample weights, and measured He. Stratigraphic height is relative to the K-Pg at 0cm. Carbonate fraction
values were provided by Dr. Julio Sepilveda and Prof. Laia Alegret. Sample weights and measured He reflect the sum of values for
all replicates. Initial and final weights were measured before and after treatment with acetic acid.
LA)
3
4
Stratigraphic
Height (cm)
Number of
Replicates
Carbonate
Fraction
Initial Weight
(3)
Final Weight
(3)
He
(10-15 cc STP)
He
(10-' cc STP)
Caravaca
-850
-740
-680
-650
-580
-550
-500
-400
-350
-300
-200
-175
-125
-77.5
-52.5
-26.5
-16.5
-11
2
4
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
0.69
0.69
0.38
0.71
0.75
0.77
0.74
0.80
0.67
0.65
0.51
0.72
0.67
0.73
0.68
0.69
0.64
0.79
2.1812
4.0739
2.0470
2.0472
2.0493
2.0268
2.0351
2.2495
2.0282
2.2322
2.2934
2.3244
2.3455
2.2504
2.2495
2.2404
2.2851
1.9420
0.4760
0.7932
0.4391
0.3630
0.5355
0.5822
0.8278
0.5375
0.5771
0.5060
0.6321
0.6001
0.7233
0.6051
0.5641
0.5415
0.6041
0.5175
29.9
64.5
27.2
22.5
29.6
35.9
32.0
55.9
38.3
24.2
34.2
31.3
26.8
28.7
26.5
26.7
45.4
80.3
303.8
514.5
297.3
285.3
381.9
537.6
660.6
380.5
449.7
333.3
323.7
257.8
354.5
261.5
284.3
256.9
257.4
834.6
;0
Table 5. (continued)
Stratigraphic
Height (cm)
3
He,
4He
Number of
Carbonate
Initial Weight
Final Weight
Replicates
Fraction
(3)
(3)
(10-1 cc STP)
(10-' cc STP)
2
a/a
n/a
0.7839
22.2
18.2
24.8
19.3
12.5
263.6
292.0
13.9
173.8
175.0
199.5
El Kef
-540
-240
-10
0.5
5
10
20
70
100
120
0.49
0.37
0.7970
1.0059
Q.6304
0.28
0.5015
2
0.19
0.21
0.4952
0.5086
0.5206
0.6586
0.5646
0.4877
0.4358
0.4369
0.4730
2
2
2
0.28
0.29
0.37
0.5548
0.5623
0.8176
0.4608
0.44360.5953
12.9
18.5
14.3
21.3
2
2
3
3
3
2
2
2
U/a
6.1190
0.0489
195.5
140.6
0.97
0.12
0.0607
1.2399
125.2
91.7
178.0
0.7500
162.4
151.9
177.5
0.77
0.83
4.0855
1.3461
1.2415
1.8839
1.6369
2.0855
312.0
265.6
0.96
6.0964
0.6859
0.3534
0.3343
0.2083
2
2
2
1
2
271.6
200.0
146.2
218.6
280.2
Hojerup
-51
-10
1
2
3
5
6
8.25
0.36
0.60
272.7
464.6
381.7
257.3
257.3
173.0
Table 5. (continued)
Number of
Replicates
Carbonate
Fraction
Initial Weight
Final Weight
3He
4He
(3)
(3)
(10-15 cc STP)
(10-' cc STP)
-105
-6
-3
4
2
p/a
16.1096
379.1
12.0084
138.8
158.3
4
0.96
209.7
354.3
0.5
1.95
4.45
10.65
16.65
2
2
2
0.13
16.1932
0.4598
1.0835
0.2111
0.1301
0.3766
0.3038
0.3607
0.3685
481.9
va
127.1
198.6
257.1
309.0
355.3
183.2
322.7
354.7
413.2
491.9
23.65
40
1
2
3
187.3
238.1
172.2
122.5
Stratigraphie
Height (cm)
Kulstirenden
45
2
2
0.56
0.63
0.73
0.75
0.9058
1.5057
1.6189
0.3802
0.3755
0.79
0.96
0.9769
12.5862
0.99
9.0141
0.1848
1.0086
0.1337
148.5
166.0