Character, Distribution and Timing of Latest
Quaternary Mass-Transport Deposits
in Texas–Louisiana Intraslope Basins Based
on High-Resolution (3.5 kHz) Seismic Facies
and Piston Cores
H.C. Olson and J.E. Damuth
Abstract Systematic mapping of 3.5 kHz seismic facies (echo character) reveals the
geometry, scales and distribution of Late Quaternary mass-transport deposits (MTDs)
within the northern Gulf of Mexico (GOM) intraslope basin province and adjacent
Sigsbee Abyssal Plain. The 3.5 kHz seismic facies indicate that localized MTDs are
common in the intraslope mini-basins. MTDs of larger scale occur on the upper
continental slope (e.g. East Breaks Slide Complex) and seaward from the eastern
base of the Sigsbee Escarpment. Approximately 120 piston cores from these deposits
“ground truth” the seismic facies interpretations and reveal that the sedimentary facies
of the MTDs in intraslope basins contain a spectrum of slumps, slides and debris flows.
Most MTDs are muddy deposits, but sandy MTDs are also common. The presence
of sandy debris flows suggests that similar, more deeply buried MTDs may constitute
significant reservoir sands. Many piston cores containing MTDs were biostratigraphically and chemically zoned using G. menardii complex and calcium carbonate fluctuations to determine the timing and sourcing of MTDs in relation to glacio-eustatic
sea-level changes associated with the Last Glacial and Holocene. This stratigraphic
analysis indicates that the majority of downslope transport (including sandy turbidites,
sandy and muddy debris flows, and slumps) occurred during the Last Glacial cycle.
Downslope transport of MTDs during the Holocene Interglacial was rare.
Keywords Mass-transport deposits • slumps • slides • debris flows • intraslope
basins • Gulf of Mexico • Late Quaternary glacio-eustatic sea-level changes • piston
cores • seismic facies • planktonic foraminifera
H.C. Olson ()
Institute for Geophysics, Jackson School of Geosciences, The University of Texas,
10100 Burnet Rd., Bldg. 196 (ROC), Austin, TX 78758, USA
e-mail: olson@ig.utexas.edu
J.E. Damuth ()
Department of Earth and Environmental Sciences, University of Texas, 500 Yates St.,
107 Geoscience Bldg., Arlington, TX 76019, 817-272-2976
e-mail: damuth@uta.edu
D.C. Mosher et al. (eds.), Submarine Mass Movements and Their Consequences,
Advances in Natural and Technological Hazards Research, Vol 28,
© Springer Science + Business Media B.V. 2010
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1
H.C. Olson and J.E. Damuth
Introduction
The northern Gulf of Mexico is one of the best studied hydrocarbon provinces in
the world. However, the majority of studies have focused on Cenozoic sedimentation
and tectonic history, and relatively few studies have focused on the latest Quaternary
sediments and their depositional processes in intraslope basins. Studies of Late
Quaternary or “Modern” analogues can potentially provide excellent exploration
models for predicting sediment facies and sand-body geometries of more deeply
buried productive deposits. A better understanding of the depositional processes
and lithology of the uppermost seafloor (upper 10–50 m) also promotes better
risk assessment in selecting the safest locations for the placement of seabed
structures related to the exploitation of hydrocarbons, including templates, piles
and pipelines.
From 1998 to 2006 the industry-sponsored Gulf of Mexico Intraslope Basins
(GIB) Project (Phases 1 and 2) produced a detailed, comprehensive and integrated
synthesis of the late Quaternary depositional processes and facies in intraslope
basins of the northern Gulf of Mexico (Olson and Damuth 2000, unpublished proprietary study; Damuth et al. 2006, unpublished proprietary study) (Fig. 1). These
studies revealed that mass-transport deposits (MTDs) are very common throughout
the study area (Fig. 1). Here, we present an overview of these mass-transport deposits
based on interpretation of high-resolution (3.5 kHz) seismic facies, sedimentology
and biostratigraphy to describe the distribution and lithologies of these MTDs, and
to understand the influence of glacio-eustatic sea-level changes on control of masstransport deposition. In this paper we use the term mass-transport deposits (MTDs)
to include slides (brittle deformation), slumps (plastic deformation) and debris
flows (plastic flow), as well as a combination of these deposits.
2
Data and Methods
A wide variety of very high-resolution data sets (seismic reflection, side-scan sonar,
swath bathymetric maps, shallow piston cores) were utilized to effectively examine
the details of latest Quaternary intraslope basin deposits (Fig. 1; contact the authors
for a map showing data coverage). We described 432 piston cores and interpreted
their depositional processes. The cores were collected and archived by the Institute
for Geophysics, The University of Texas at Austin (UTIG) and by the U.S.
Geological Survey. Core lengths range up to 12 m and average 4 to 5 m. The
71,000 km of 3.5 kHz seismic data interpreted were short ping (<5 ms) echograms
acquired by UTIG during a large number of cruises conducted since the mid-1970s
and by the U.S. Geological Survey during their survey of the U.S. Exclusive
Economic Zone with the GLORIA long-range side-scan sonar (EEZ-SCAN 85
Scientific Staff 1987). These echograms complement our piston-core studies in the
GIB study area because the 3.5 kHz records can resolve beds on the order of 12 cm,
and thus reflections can sometimes be directly correlated with discrete beds, physical
Fig. 1 Bathymetric map of the GIB Phase 1 study area in the northern Gulf of Mexico Intraslope Basin Province. The distribution of mass-transport deposits
on the seafloor as mapped with 3.5 kHz seismic data is shown by the orange (Facies 1) and red (Facies 2) patterns (Olson and Damuth 2000) (see text for
details). Bathymetric Data Sources: Shaded Swath Bathymetry (Sea Beam) from NOAA (NGDC). Bathymetric contours (blue) from Smith and Sandwell
(1997) (Contour Interval = 100 m). Inset map shows location (Seafloor Relief Map compiled by Liu and Bryant (2000). Locations of piston cores (dots) and
seismic profiles (lines) illustrated in Figs. 2–5 are shown above and identified by figure number (e.g. 2A)
Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits
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H.C. Olson and J.E. Damuth
properties, or other deposits (e.g. slumps, debris flows, sand beds, etc.) in the cores.
To interpret the regional distribution of MTDs and other depositional processes,
we constructed an echo character map of various 3.5 kHz seismic facies or ‘echo
types’ of bottom echoes following the methodology of Damuth (1975a, 1980, and
references therein).
Stratigraphic analysis of the latest Quaternary stratigraphy of a subset of 131
piston cores, including 58 with MTDs, was undertaken to determine the relationship
of MTDs and other depositional processes to glacio-eustatic sea-level fluctuations.
Foraminiferal biostratigraphy, especially fluctuations of G. menardii complex,
along with fluctuations of coarse-fraction and carbonate contents were used to
determine the latest Quaternary glacial/interglacial cycles in the cores (Kennett and
Huddlestun 1972a, b; Ericson and Wollin 1968; Damuth 1975b; Prell and Hays
1976; Prell and Damuth 1978; Martin et al. 1990). These zonations and curves
provide a stratigraphic framework that permits correlation of cores and glacial/
interglacial cycles from basin to basin throughout the study area, as well as
determination of the timing of mass-transport deposition.
3
3.1
Results
Seismic Character and Regional Distribution of MTDs
Seismic facies representing mass-transport deposits are very common throughout
the study area. These MTDs return two distinctive 3.5 kHz seismic facies: Facies 1
returns sharp to prolonged bottom echoes with transparent internal character, commonly bounded by irregular wedge, mound, fill or lens shaped external forms
(Fig. 1, orange pattern; Fig. 2a–c) and Facies 2 returns regular, overlapping to
singular hyperbolic bottom echoes with varying vertex elevations (Fig. 1, red
pattern; Fig. 2c and d). Numerous studies have documented that these two facies,
especially Facies 1, are characteristic of MTDs imaged by 3.5 kHz profiling (e.g. see
Damuth 1980 for review and references). These two facies are sometimes intergradational (e.g. Fig. 2c). Many additional areas of Facies 1 and 2 were observed and
mapped in the intraslope-basin floors, but they cannot be displayed on Fig. 1
because of the small figure size.
The majority of MTDs found on intraslope-basin floors, along the upper continental slope, within portions of the East Breaks Slide Complex, east of the base of
the Sigsbee Escarpment and on the southwestern portion of the Mississippi Fan
(Fig 1) are Facies 1 (Fig. 2a–c). This facies is interpreted as deposits of mainly
debris flows and some slumps. This facies has been cored at numerous locations
and the cores confirm this interpretation (e.g. Figs. 3 and 4; see discussion below).
The large area of Facies 1 in the southeast corner of the study area (Fig. 1) represents the toe of a much larger MTD on Mississippi Fan, which was first identified
and mapped by Walker and Massingill (1970).
Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits
611
Fig. 2 Examples of 3.5 kHz seismic records from the northern Gulf of Mexico Intraslope Basin
Province (Fig. 1) showing examples of seismic facies (1 and 2) interpreted as mass-transport
deposits. (a, b) Mass-transport deposits in intraslope basin displaying characteristics of Facies 1
(orange pattern in Fig. 1). (c) Mass-transport deposits in an intraslope basin that return both Facies
1 and 2. (d) Mass-transport deposits from the East Breaks Slide Complex that return Facies 2 (red
pattern in Fig. 1). Locations of profiles shown in Fig. 1
The distribution of Facies 2 is less common throughout the study area (Fig. 1).
The most extensive area is returned from the East Breaks Slide Complex in the
northwestern part of the study area (Figs. 1 and 2d). In this area, Facies 2 is associated
with Facies 1. Facies 2 is also interpreted as gravity-controlled mass-transport
deposits, which are mainly slumps and slides. Coherent or deformed blocks of
various sizes that make up these deposits produce a rough sea-floor microtopography,
which, in turn, is recorded as a series of small overlapping to single hyperbolae of
slightly variable sizes on 3.5 kHz profiles (Fig. 2c and d). Cores recovered from
areas returning Facies 2 confirm the interpretation of this facies as mass-transport
deposits (see below).
3.2
Lithology of MTDs in Piston Cores
A large number of cores were taken from areas of 3.5 kHz Facies 1 and 2 (Fig. 1).
Mass-transport deposits occur in the majority of these piston cores as evidenced by
the presence of chaotic deposits that can clearly be interpreted as slumps, slides
and debris flows (Figs. 3–5). These cores provide confirmation or “ground truth”
0
300
200
100
P
CSFMCG
Isoclinal
Folds
100
0
400
300
200
P
P-Location of Photographs
P
C SFMCG
5 cm
5 cm
Fig. 3 Examples of piston cores from intraslope basins with mass-transport deposits. (a) Core IG36-3 showing close-up photographs of mud-rich debris-flow
deposits composed of highly deformed and folded exotic-colored mud clasts. Graphic core log at left. (b) Core IG45-20 showing close-up photographs of
sandy mass-transport deposit with large exotic mud clasts. Graphic core log at left. Locations of cores shown in Fig. 1
P-Location of Photographs
700
600
500
400
Centimeters
b
Centimeters
a
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H.C. Olson and J.E. Damuth
Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits
613
Fig. 4 (a) Core IG38-26 showing close-up photographs of a slump deposit in an intraslope basin.
The 3.5 kHz seismic line shows that the core was taken from Facies 1 typical of slump/debris flow.
(b) Core IG41-24 showing close-up photographs of a sandy mass-transport deposit with a matrix
of fine to medium sand and large mud and rock clasts. The 3.5 kHz seismic line shows that the
core was taken from Facies 1 typical of slump/debris flow. Locations of cores shown in Fig. 1
for the seismic interpretations. These MTDs contain thick intervals of disturbed,
deformed bedding and layers that show variable dips, discordance, truncations,
soft-sediment flowage and folds. Exotic colored (e.g. brick reddish brown) layers
and variable lithologies are common and many intervals contain angular to rounded
mud clasts of various sizes, shapes and colors. We generally interpret the dipping,
discordant and folded intervals as slump or slide deposits (e.g. Fig. 4a) and the
deposits of mud or rock clasts as debris flows (e.g. Figs. 3, 4b and 5). Of the 432
cores described, 123 contain mass-transport deposits. The depositional facies distribution is: debris flows in 96 cores, slumps in 51 cores, and slides in 8 cores (Figs.
3–5). Combinations of two or more of these processes were observed in 36 cores.
The majority of slumps and debris flows are muddy deposits (Figs. 3a, 4a, and 5),
but sandy debris flows are also present (Figs. 3b and 4b). Muddy mass-transport deposits are commonly cored on the East Breaks Slide Complex (Fig. 5).
Several cores taken in mass-transport deposits recovered sandy debris-flow
deposits that consist of medium- to coarse-sand matrix with large exotic mud or
rock clasts (Figs. 3b and 4b). The 3.5 kHz seismic facies at some of these core sites
return 3.5 kHz Facies 1 consistent with mass-transport deposits (e.g. Fig. 4b);
however, there currently are no criteria for predicting muddy versus sandy slump/
debris-flow deposits based solely on the 3.5 kHz seismic facies character alone.
614
H.C. Olson and J.E. Damuth
a
90L566-11
G.menardii Index
Lithology
C SFMCG
0.4
0.0
0.8
1.2
0
Z
Mass
Transport
Deposit
DEPTH (CM)
50
100
Y
150
200
G.flexuosa displaced from
x Zone or older sediments
by mass-transport processes
250
East Breaks Slide Complex--Western Lobe
166-210 cm
b
91L575-9
Lithology
G.menardii Index
0.0
C SFMCG
0.4
0.8
1.2
0
Void
Void
DEPTH (CM)
Z
100
200
Y
300
295-311 cm
265-282 cm
East Breaks Slide Complex--Western Lobe
Fig. 5 Lithology, G. menardii index stratigraphy and close-up photos of cores from the East Breaks
Slide Complex showing the timing of deposition of mass-transport deposits in relation to latest
Quaternary climatic cycles. (a) The G. menardii Index curve for Core 90L566-11 shows that a
muddy debris flow with large exotic mud clasts was emplaced during the latest part of the Y zone
or Last Glacial. Note that G. flexuosa, which was deposited in sediments of the Last Interglacial (X
zone) or older interglacials, were entrained in the MTD. (b) The G. menardii Index curve for Core
91L575-9 shows that a muddy debris flow followed by a sandy turbidite were deposited during the
latest Y zone or Last Glacial. See text for additional discussion. Locations of cores shown in Fig. 1
The occurrence of sandy MTDs in modern intraslope basins has important implications
for hydrocarbon exploration because these modern analogues imply that sand bodies consisting of mass-transport deposits may be present in deeply buried productive
Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits
615
zones of the GOM. MTD sand bodies will probably exhibit much different reservoir
geometries than ponded turbidite reservoirs or small submarine fans in intraslope
basins because plastic debris flows tend to “freeze” in place and produce thick sand
bodies of irregular shape. These MTD sand bodies will have much different reservoir geometries than laterally extensive turbidites, and so, must be properly imaged
and identified to accomplish efficient hydrocarbon production.
3.3
Relationship of MTDs to Glacio-eustatic Sea-Level Changes
Stratigraphic analysis of cores containing MTDs using the methods described
above reveals the timing of mass-transport events within the intraslope basins in
relation to glacial/interglacial cycles. Mass-transport deposition during the Holocene
(Z zone) is very rare. The majority (99%) of cores stratigraphically analyzed show
that mass-transport events occurred mainly during the Last Glacial cycle (Y zone)
(e.g. Fig. 5). Most of the Y zone mass-transport deposits indicate that sediments
were not only deposited during the glacial cycle, but were likely derived from
glacial deposits (Y zone) because they do not contain G. menardii complex (only
present during interglacials). However, in the East Breaks Slide Complex sediments
originally deposited during the Last Interglacial (X zone) were remobilized during
the Last Glacial (Y zone) as evidenced by the presence of G. flexuosa (which does
not occur in sediments younger than the Last Interglacial) in some Y-zone age
MTDs (e.g. Fig. 5a).
Several cores in the study area show a pattern of Y zone slumps and debris flows
directly overlain by sandy turbidites (e.g. Fig. 5b). Both the mass-transport deposits
and the overlying turbidites were deposited in the Y zone and do not contain any
G. menardii components. In these cores, a single event may have triggered a slump
or debris flow followed by a turbidity flow (e.g. Fig. 5b).
4
Conclusions
1. Interpretation of 3.5 kHz seismic facies in the Gulf Intraslope Basin Provence
shows that localized MTDs, including slumps, slides and debris flows, are very
common throughout the intraslope mini-basins of the region. In addition, large
areas along the upper continental slope, portions of the East Breaks Slide
Complex, seafloor east of the base of the Sigsbee Escarpment, and the southwestern portion of the Mississippi Fan have extensive MTDs.
2. Numerous piston cores taken from these MTD-interpreted seismic facies, especially in the intraslope basins, contain a variety of debris flows, slumps and
slides, and provide “ground truth” of the seismic data. These chaotic deposits
display thick intervals of disturbed, deformed bedding and layers that show
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H.C. Olson and J.E. Damuth
variable dips, discordance, truncations, flowage and folds, and are interpreted as
slumps and slides. Exotic colored layers and lithologies and intervals containing
angular to rounded mud clasts of various sizes, shapes and colors are interpreted
as debris flows.
3. Sandy debris flows composed of fine- to medium-sand with mud and rock clasts
are also present but much less common. However, the occurrence of sandy
MTDs in modern intraslope basins has important implications for hydrocarbon
exploration because these modern analogues imply that sandy MTDs form sand
bodies in deeply buried productive zones of the GOM and will have different
geometries than laterally extensive turbidite deposits.
4. Stratigraphic analysis and zonations of many cores containing MTDs show that
nearly all MTDs were deposited during glacio-eustatic sea-level lowstands such
as the Last Glacial (Y zone). Deposition of MTDs during glacio-eustatic highstands such as the Holocene (Z zone) or perhaps even the Last Interglacial
(X zone) has been extremely rare.
Acknowledgments We thank the following companies who supported the Gulf of Mexico
Intraslope Basins (GIB) Project Phases 1 and 2: ENI (AGIP), Anadarko, BP, Amoco, Vastar,
Conoco-Phillips, Marathon, Spirit Energy/Unocal, Texaco, Repsol YPF, Statoil, Norsk Hydro and
TotalFinaElf. Patty Ganey-Curry was extremely effective as our project manager/industry representative. The U.S. Geological Survey provided financial support to study the USGS 97G06 cores.
Peter Thompson, Graham Moss, Adam Skarke, George Sayre, Ilene Rex Corbo, and Bill Abbott
helped with biostratigraphic analyses. We thank Shana Wells and W.A. Balsam at The University
of Texas at Arlington for assistance with carbonate analyses. Tim Whiteaker, David Dunbar and
Lisa Bingham provided assistance with GIS compilation of the database. Laurie Powery, Gwen
Watson, Randy Schmitz and Peter Abel provided helpful support with graphics, drafting and mapping. Lisa Gahagan provided computer and technical support throughout the project.
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