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The Record of Pliocene SeaThe Record of Pliocene Sea--Level Change At Level Change At EnewetakEnewetak AtollAtoll
Bruce W. Bruce W. WardlawWardlaw and Terrence M. Quinnand Terrence M. QuinnQuarternaryQuarternary Science ReviewsScience Reviews, Vol. 10, pp. 247, Vol. 10, pp. 247--258, 1991.258, 1991.
Steven Steven ScyphersScyphersGeological OceanographyGeological Oceanography
3/20/20083/20/2008
When?When?
Pleistocene: 1.8 Ma to 11.5 KaPleistocene: 1.8 Ma to 11.5 Ka
Pliocene: 5.3 Ma to 1.8 MaPliocene: 5.3 Ma to 1.8 Ma
Where is PEACE?Where is PEACE?PurposePurpose
Reconstruct sea level based upon Reconstruct sea level based upon stratigraphicstratigraphicdistribution of major distribution of major disconformitiesdisconformities that that coincide with resolvable age differences in the coincide with resolvable age differences in the biochronologybiochronology
StratigraphyStratigraphy= study of distributions, = study of distributions, deposition, and age of sedimentary deposition, and age of sedimentary rocksrocks
Litho= physical and Litho= physical and petrographicpetrographic propertiesproperties
Chemo= dating marine sediments/rocks using trace Chemo= dating marine sediments/rocks using trace elements, molecular fossils, isotopic ratioselements, molecular fossils, isotopic ratios
Seismic= Reflection character analysisSeismic= Reflection character analysis
Bio= based upon fossil content Bio= based upon fossil content
Disconformities= surface between successive Disconformities= surface between successive strata, representing a missing interval in strata, representing a missing interval in geologic timegeologic time
OverviewOverview
Previous studies: Previous studies: Single Bore HoleSingle Bore HoleSingle Isotope (Single Isotope (SrSr))
Discrepancies due with intraDiscrepancies due with intra--lagoon variability when lagoon variability when compared with compared with biochronologybiochronology
This study: Six Bore HolesThis study: Six Bore HolesMultiple ApproachesMultiple Approaches
-- Sequence Sequence StratigraphyStratigraphy ModelModel-- Isotope ModelIsotope Model
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Seismic Seismic StratigraphyStratigraphy
-utilizes equipment that produces vibrations and allows their behavior in the substrate to be recorded
Seismic Seismic StratigraphyStratigraphy
Results:Results: 9 Major Disconformities in 9 Major Disconformities in PEACE BoreholesPEACE Boreholes
6 within the 6 within the PlioPlio--Pleistocene Pleistocene
2 Shallow Reflections correlate exactly with 2 Shallow Reflections correlate exactly with disconformitiesdisconformities
ChemostratigraphyChemostratigraphy
Literature on sediments states:Literature on sediments states:Holocene = unaltered aragonite Holocene = unaltered aragonite PlioPlio--Pleistocene= mixed mineralogy of Pleistocene= mixed mineralogy of aragonite/calcitearagonite/calcitePliocene= altered calcite Pliocene= altered calcite
Low Low δδ1313 C and C and δδ1818 O relate to meteoric O relate to meteoric calcitizationcalcitization
ChemostratigraphyChemostratigraphy
BiostratigraphyBiostratigraphy
------------ Upper and Lower Upper and Lower PaleoPaleo Lines of Lines of CorrelationCorrelation
_____ Line of Correlation_____ Line of Correlation
Windows of Correlation Windows of Correlation define distance between define distance between disconformitiesdisconformities
Sea Level Sea Level HighStandHighStand ModelsModels
25 and 40 m/Ma Subsidence Rates for Isotope Proxy Model and Sequence Stratigraphy Model
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Sea Level EstimatesSea Level Estimates
Considering minor disconformities, Sea Level Falls were probably less than the depth of the Lagoon.
PlioPlio--Pleistocene Ice Volume, Antarctic Pleistocene Ice Volume, Antarctic Climate, and the Global Climate, and the Global δδ1818 O RecordO Record
M.E. M.E. RaymoRaymo, L.E. , L.E. LisieckiLisiecki, K.H. , K.H. NisanciogluNisanciogluScience. Science. Vol. 313. 28 July 2006Vol. 313. 28 July 2006
Steven Steven ScyphersScyphersGeological OceanographyGeological Oceanography
3/20/20083/20/2008
ObjectivesObjectives
Present a simple model of ice volume Present a simple model of ice volume change that predicts sea level change and change that predicts sea level change and δδ1818 OO that matches geological record.that matches geological record.
Evaluate the relative Evaluate the relative importancesimportances of of obliquity and precession to obliquity and precession to cyclicitycyclicity..
AssertionsAssertions
23k year orbital precession cancels out 23k year orbital precession cancels out globally.globally.
41k year in41k year in--phase phase obiquityobiquity is the is the component of component of insolationinsolation that dominates that dominates the records.the records.
ObliquityObliquity
The angle of axial tiltThe angle of axial tilt
Lower Obliquity Lower Obliquity
Lower Solar Lower Solar RadationRadationat Polesat Poles
Increased Increased GlaciationGlaciation
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PrecessionPrecession--dV/dtdV/dt = (i + V)/ = (i + V)/ t
Relationship of Relationship of accumulation and accumulation and abrasionabrasion
Milankovitch Model Output
ConclusionsConclusions
Obliquity and Precession are both factorsObliquity and Precession are both factorsObliquity in phase between polesObliquity in phase between polesPrecession out of phase between polesPrecession out of phase between poles
LongLong--term cooling could transition term cooling could transition primarily land based to marine based East primarily land based to marine based East AnarcticaAnarctica Ice SheetIce Sheet
ConclusionConclusion
Small Changes in Small Changes in AnarcticAnarctic Ice Mass could Ice Mass could cancel out much larger changes in N.H.cancel out much larger changes in N.H.
The TerrestrialThe Terrestrial--Marine Shift could result in Marine Shift could result in strengthening of the 23k cycle in the strengthening of the 23k cycle in the marine marine δδ1818 O O