The Record of Pliocene SeaSea-Level Change At
Enewetak Atoll
Bruce W. Wardlaw and Terrence M. Quinn
Quarternary Science Reviews, Vol. 10, pp. 247247-258, 1991.
Steven Scyphers
Geological Oceanography
3/20/2008
When?
„
Pleistocene: 1.8 Ma to 11.5 Ka
„
Pliocene: 5.3 Ma to 1.8 Ma
Where is PEACE?
Purpose
Reconstruct sea level based upon stratigraphic
distribution of major disconformities that
coincide with resolvable age differences in the
biochronology
„
Stratigraphy=
Stratigraphy= study of distributions,
deposition, and age of sedimentary
rocks
„
Litho= physical and petrographic properties
„
Chemo= dating marine sediments/rocks using trace
elements, molecular fossils, isotopic ratios
„
Seismic= Reflection character analysis
„
Bio= based upon fossil content
Overview
„
„
„
„
Disconformities= surface between successive
strata, representing a missing interval in
geologic time
Previous studies:
Single Bore Hole
Single Isotope (Sr
(Sr))
Discrepancies due with intraintra-lagoon variability when
compared with biochronology
This study: Six Bore Holes
Multiple Approaches
- Sequence Stratigraphy Model
- Isotope Model
1
Seismic Stratigraphy
Seismic Stratigraphy
„
Results:
9 Major Disconformities in
PEACE Boreholes
„
„
6 within the PlioPlio-Pleistocene
2 Shallow Reflections correlate exactly with
disconformities
-utilizes equipment that produces vibrations and allows their behavior in the
substrate to be recorded
Chemostratigraphy
„
Literature on sediments states:
„
„
„
„
Chemostratigraphy
Holocene = unaltered aragonite
PlioPlio-Pleistocene= mixed mineralogy of
aragonite/calcite
Pliocene= altered calcite
Low δ13 C and δ18 O relate to meteoric
calcitization
Biostratigraphy
Sea Level HighStand Models
------ Upper and Lower
Paleo Lines of
Correlation
_____ Line of Correlation
Windows of Correlation
define distance between
disconformities
25 and 40 m/Ma Subsidence Rates for Isotope Proxy Model and Sequence
Stratigraphy Model
2
Sea Level Estimates
Considering minor disconformities, Sea Level Falls were probably less than the
depth of the Lagoon.
PlioPlio-Pleistocene Ice Volume, Antarctic
Climate, and the Global δ18 O Record
M.E. Raymo,
Raymo, L.E. Lisiecki,
Lisiecki, K.H. Nisancioglu
Science. Vol. 313. 28 July 2006
Objectives
„
Steven Scyphers
Geological Oceanography
3/20/2008
„
Present a simple model of ice volume
change that predicts sea level change and
δ18 O that matches geological record.
Evaluate the relative importances of
obliquity and precession to cyclicity.
cyclicity.
Assertions
„
„
23k year orbital precession cancels out
globally.
41k year inin-phase obiquity is the
component of insolation that dominates
the records.
Obliquity
„
The angle of axial tilt
„
Lower Obliquity
Lower Solar Radation
at Poles
Increased Glaciation
3
-dV/dt = (i + V)/ t
Precession
„
Relationship of
accumulation and
abrasion
Milankovitch Model Output
Conclusions
„
Obliquity and Precession are both factors
„
„
„
Obliquity in phase between poles
Precession out of phase between poles
LongLong-term cooling could transition
primarily land based to marine based East
Anarctica Ice Sheet
Conclusion
„
„
Small Changes in Anarctic Ice Mass could
cancel out much larger changes in N.H.
The TerrestrialTerrestrial-Marine Shift could result in
strengthening of the 23k cycle in the
marine δ18 O
4