Geologist Indonesia

1. Paleoceanography
Is a study of development of ancient
ocean system based on the information
available from the sedimentary material
including microfossils.

2. Material
• Most paleo-information taken from sediment cores
• Extremely expensive to collect, hence valuable
• Deep Sea Drilling Program (DSDP), Ocean Drilling
Program (ODP)
• International Ocean Drilling Program (IODP),
Glomar Explorer
• Ocean sediment record limited to about 180 million
years.
• Study of paleoceanography is based on microfossils
especially foraminifera, nannofossils and isotope
(Oxygen and carbon).

3. History
• Beginning in 1968, an enormous amount of effort in this
subject, especially through the work of the CLIMAP
group in Pleistocene oceanography, and through the
extensive drilling in the deep sea by Glomar Challenger.

4. Nature of paleoceanography
• Paleoceanography includes:-
– Study of water circulation (surface and
bottom currents)
– Planktic and benthic development and
evolution
– History of biogenic productivity and its effect
on sediment distribution
– History of Carbonate and silica deposition and
dissolution.

5. Proxies in paleooceanography
• Microfossils
• Remnants (inorganic structures or organic chemicals) of
specific species.
• Modern day activity of these species is extrapolated to
the past (warm-water species vs. cold, specific diversity,
coiling directions and productivity of microfossils.
• Isotopic Composition of carbon and oxygen isotopes
• - Measure how much of the heavy and light isotope
there is in the sediments .
• -The relative abundance of the heavy and light isotope
(i.e. the isotopic composition) depend on ocean
conditions….especially climate
• -

6. Oxygen Isotopes and climate
• Perhaps no tool has been more highly utilized for
paleoclimate reconstruction than δ O18. Early work by
Sam Epstein at Caltech opened the field of quantitative
paleoclimate research.
– O16 - 99.8% of the oxygen present
– O18 accounts for most of the rest. O18/O16 ~ 1/400.
• The changes in Oxygen isotope 18 is expressed by
• δO18 = [(O18/O16)sample – (O18/O16)standard] X 1000
(O18/O16)standard
• Standard is taken from CaCO3 from Cretaceous
belemnite obtained from Pee Dee Formation, South
Carolina

7. • The utility of oxygen isotopes as paleothermometers has
to do with the fractionation that occurs during
evaporation and condensation of water and in the
formation of CaCO3.
• During evaporation, δO18 of the vapor is less than that of
the source because the heavier isotope is preferentially
retained.
• When this water condenses, again, the heavier isotope
is preferentially condensed and the vapor becomes ever
lighter.
• The net movement of water vapor poleward by the
atmospheric hydrological cycle produces a latitudinal
gradient in δ O18 with the heavier isotope preferentially
retained in the tropics. Snow falling at high latitude is
very depleted in O18 and thus formation of glaciers leads
to enrichment in oceanic O18 while melting of the ice
caps reduces this enrichment.

8. Paleothermometry – using
carbonates
• Epstein Equation:
• T= 16.9 – 4.2 (δO18c – δO18w)
• where δO18c is from the calcite shells of foraminifera
• δO18w is the mean value of ocean water when the shells
formed.
• t (ºC) = 16.9 – 4.14(δ 18Ocalcite – δ 18Owater) + 0.13(δ 18Ocalcite – δ 18Owater)2

9. Paleoclimate curve

10. δO18c in benthic foraminifera record the longterm
cooling of the deep ocean. K.G. Miller et al.,
Paleoceanography 2, 1, 1987.

12. Types of climate
• There are two modes of climate
– Warm (green-house)
– Cold (ice-house)
– Paleoceanographic conditions can be divided
into two types.
Polytaxic
Oligotaxic

13. Polytaxic condition
• Develop during the warm period, No glacier in the
polar regions.
• Ocean less stratified
• Poorly developed thermocline
• Paleogeographic provinces not well-developed
• Bottom currents weak
• No thermohaline circulation
• Ocean bottom poorly oxygenated
• Development of black shale due to reducing
condition at the sea-bottom.
• Relatively higher number of species

14. Oligotaxic condition
• Develop during the glacial period the oceans are
stratified warm water near the surface and cold water at
the bottom.
• Well developed thermocline
• Paleogeographic provinces are well developed.
• Strong cold dense bottom currents developed.
Oxygenated bottom of the ocean.
• Development of thermohaline circulation. Strong bottom
currents
• A lot of erosion and hiatuses
• Relatively low number of species.
• Nunber of species higher in Tropic and reducing towards
the poles

15.  A drastic increase in oxygen isotope values in
benthic foraminifera between 15 and 13 million
years ago.
• This increase reflects both
growth of ice on Antarctica
and a world wide cooling of
abyssal waters.
• A substantial carbon
isotope excursion toward
heavy values
• Synchronous with the onset
of abundant sedimentation
of organic-rich sediments in
the margins of the Pacific.

16. Paleogeography
 All through the Tertiary, changes in geography due
to plate motions affect the configuration of exchange
between ocean basins.
 The gateways control access to the Arctic Ocean
(east and west of Greenland), connnect the global
ocean along the Equator ("Tethys Ocean" between
Africa and Eurasia, Panama Straits, Indonesian
Seaway between Borneo and New Guinea), and
control the evolution of the Circumpolar Current
(Tasmanian Passage, Drake Passage).

17. The Great Partitioning
Fig.9.12 Geography of the middle Eocene (ca 45 Ma) and major critical valve
points for ocean circulation. Tropical valves are closing (filled rectangles),
high latitude valves and opening up (open rectangles) throughout the
Cenozoic.[Base map from B. U. Haq, Oceanologica Acta, 4 Suppl.:71]

18. Example of using microfossils to ‘reconstruct’ change in ocean current pattern
Warm water surface circulation cut off between N. and S. America.

19. Tertiary Oxygen Isotope Record
• An overall cooling trend since the Cretaceous, from the
increase of oxygen-18 in benthic foraminifera.

20. T°C
Cretaceous
Pleistocene
Plio-
Paleo. Eocene Oligocene Miocene
"ice free"
-1 Antarctic Ice Sheets 14
12
0 10
N Hem
. isphere Ice Sheets
8
δ18O ä
1 6
possibly ice free 8
4
2 2
6
ice sheets
4
3 2
0
4 modern
70 60 50 40 30 20 10 0
Age Ma
Modified after Miller et al.,
Paleoceanography, 2, 1-19, 1987.

21. (A) 1-My means for planktic foraminiferal assemblage sizes95/5 from tropical and subtropical sites
(squares) and from temperate and subpolar sites (triangles). The vertical line shows the mean
size95/5 (389 µm) of all assemblages. Light blue and orange shading shows ±1 standard deviations for
mean sizes95/5. Plio., Pliocene; Plt., Pleistocene. (B) The global deep-sea oxygen isotope record
representing Cenozoic polar cooling and ice accumulation (23). (C) The total number of planktic
foraminiferal species globally known per 1-My interval (18).
Correlation
based on
foraminifera

22. Atlantic and Pacific
CCD Fluctuations
• The CCD stood high in
the late Eocene,
dropped in the earliest
Oligocene, rose in the
Miocene when it
reached a peak
between 10 and 15
years ago, and then
fell to its present depth
near 4.3 km.
Fig.9.18 Reconstructions of CCD fluctuations for various oceanic regions.
Solid and dashed lines. Reconstructions of Tj. H. van Andel et al., 1977, J
Geol 85:651. Dotted line Reconstructions of W. H. Berger, P. H., 1975, Rev
Geophys Space Phys 13:561. The reconstructions agree in the general
patterns of the fluctuations, which appear correlated with sealevel changes

23. CCD Fluctuation
• An overall similarity in the CCD fluctuations of
Pacific and Atlantic: a sign that the chemical climate
of the ocean is changing on a global scale.
• Eocene and Miocene have a shallower CCD than
Oligocene and Plio-Pleistocene.
• A certain parallelism of this pattern with oxygen
isotope variations and with sea-level variations.
• Periods of high sea level are characterized by
shallow CCD and warm high latitudes; periods of
low sea level have a deep CCD and cold high
latitudes (and deep waters).

24. "Anoxic Events" and Volcanism
• The widespread occurrence of Cretaceous organic-rich
sediments
• Distinct positive excursions in the δ13C record
Fig.9.21 "Oceanic Anowic Events" of Schlanger and Jenkyns, and δ 13 C record of
pelagic marine limestones, showing coincidence of the "events" with positive δ 13 C
excursions (generated through the lock-up of 12 C-rich carbon). Width of blank band
reflects uncertainty in the value of δ 13 C . Lower part; Cretaceous stages from
Berrassian (right) to Maastrichtian (left). OAEs are centered in the Aptian,
Cenomanian/Turonian and Santonian/Campanian

25. Two Modes of Circulation
• Warm Mode
– N. Atlantic Deep Water
– Shallow Compensation
• Cold Mode
– N. Atlantic
Intermediate and
Upper Deep Water
– Deep Compensation