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Eolian dust preserved in deep-sea pelagic sediments can be used as a proxy indicator of paleoclimate. Analyses of the particle size, composition, and mass accumulation rate of dust grains provide independent evidence of the intensity of atmospheric circulation and the availability of material in the eolian source region. These data provide information on atmospheric circulation and on the climate of the source area at time scales ranging from 103 to 108 years and have the potential to test computer-generated global circulation models.

A major change in Cenozoic deep-sea benthic foraminifera occurred in the Atlantic, Indian, and Pacific oceans near the Paleocene/Eocene boundary. Benthic foraminiferal abundance changes began at about 61.5 Ma at Pacific Deep Sea Drilling Project (DSDP) Site 577. A major extinction event followed at 58-57 Ma (between Zones P6a and P6b), and a series of first appearances continued until circa 55.5 Ma (Zone P6c). These faunal changes occurred during a 6øC warming of Pacific bottom water and may indicate that the primary cause was changing temperature. Other potential causes of the faunal turnover include global changes in surface ocean productivity and changing bottom water source regions. Comparison of benthic and planktonic •513C records requires no change in the ratio of oceanic phosphorous to carbon during the late Paleocene to early Eocene, which weakens the case for (but does not disprove) a change in surface ocean productivity at this time. Interbasinal comparisons of benthic foraminiferal /513C records document that water with high/5•3C values filled the Cape Basin during the late Paleocene and possibly the early Eocene (circa 61-57 Ma), but apparently did not extend into the western basins of the Atlantic. This pattern suggests a supply of Antarctic source water for the Cape Basin and possible tectonic isolation of the western Atlantic basins during at least part of the late Paleocene. Carbon isotope comparisons show that bottom water supply to the Cape Basin was reduced in the early Eocene. Eolian grain size data suggest that a decrease in zonal wind intensity occurred at the end of the Paleocene. These late Paleocene climatic changes (bottom water warming and decreased wind intensity) correspond with evidence for an important global tectonic reorganization and extensive subaerial volcanism, which may have contributed to climatic warming through increased supply of CO2. BACKGROUND The early Paleogene high latitudes were the warmest of the Cenozoic, with peak warming in the early Eocene. Evidence for this includes low Paleocene-Eocene •5•80 values measured in deep-sea benthic foraminiferal tests [e.g., Shackleton and Kennett, 1975; Savin et al., 1975; Miller et al., 1987], low surface water •5180 values near the Antarctic coast [Barrera et al., 1987], and the presence of thermophilic terrestrial species at high latitudes [Wolfe, 1978]. Equatorial surface water temperatures may have been several degrees cooler than at present [Shackleton et al., 1985a], and latitudinal thermal gradients were lower [Shackleton and Boersma, 1981]. In addition to paleotemperature constraints obtained from stable isotope data, planktonic microfossils reflect fluctuating surface conditions for this interval. Following the cataclysmic planktonic extinctions at the end of the Cretaceous, surface water microfossils radiated into distinct latitudinal bioprovinces in the Paleocene. The bioprovinces alternately expanded and contracted in response to surface water warmings and coolings during the early Paleogene, with the warmest condit...

Scientific drilling in the high-latitude North Pacific during ODP Leg 145 has resulted in a new and detailed insight into the paleoceanographic and paleoclimatic record of this important region. Many of these accomplishments were made possible by the development of a new, much more aggressive, piston coring technique. This new technique resulted in very long APC cores which, in turn, allowed the construction of long and continuous magnetic reversal stratigraphies. Results fall into four categories, events of the Plio-Pleistocene, the Neogene, the Paleogene, and a special events category. The first category is the important changes at 2.6 Ma, the time of the onset of major Northern Hemisphere glaciation (timescale of Cande and Kent, 1992). Dropstones appear in abundance at 2.6 Ma and document sources in both Siberia and Alaska. The input of continentally derived, fine-grained elastics into the deep sea increases several fold at this time, and in the northwestern Pacific abyssal reworking of bottom sediments also begins at about 2.6 Ma and continues to the present. Finally, volcanic ash layers suddenly become abundant in sediments younger than 2.6 Ma all across the North Pacific, a volcanic event that dwarfs anything found earlier in the Cenozoic record. One of the important objectives of Leg 145 was to define better the onset and character of silica sedimentation in the North Pacific. We were able to document that opal fluxes began to increase about 12 Ma, with a pronounced maximum between about 6 and 3 Ma. Also starting in the early portion of the middle Miocene the calcite compensation depth becomes 1.5 km shallower, in marked contrast to a deepening of the CCD since the early Miocene found everywhere else in the world. Leg 145 recovered Oligocene and Eocene carbonate sediments at Detroit Seamount. The middle and upper Eocene sediments are characterized by episodes of downslope transport, reworking and slumping, the timing of which matches that of similar events in the central Pacific Basin. Several Eocene ash horizons occur, adding further definition to the poorly known Eocene volcanism history. The Meiji sediment tongue on the northeast flank of Detroit Seamount was an important drilling target. Leg 145 was able to show that the Meiji tongue is an Atlantic-type drift deposit that has been forming continuously since the early Oligocene. Many paleoceanographic implications follow this important discovery, the most important of which is the continual presence of southward thermohaline flow from the Bering Sea to the North Pacific for the past 35 million years. Leg 145

We conclude that the putative link between Ba accumulation and export production may be obscured by changes in particle composition even within a dominantly biogenic sedimentary regime, as well as by early aliagenetic transfer between phases, and that the non-barite elemental Ba inventory may complicate the use of elemental Ba as a quantitative proxy for barite in the bulk sediment.

Two major goals of Leg 108 were to investigate late Cenozoic changes in (1) North African aridity and (2) atmospheric circulation over the equatorial Atlantic and Sahelian/Saharan Africa. Several high-resolution records from Ocean Drilling Program Leg 108 are pertinent to these problems. Dust fluxes from Africa to the Atlantic were low during the final 3 m.y. of the Miocene and then increased markedly during the Pliocene and Pleistocene. The increasing Pliocene-Pleistocene dust fluxes suggest major aridification of North Africa, possibly accompanied by an increase in the amplitude of aridity/humidity cycles. Other evidence from the northwest African margin (influxes of fluvial clay, terrestrial carbon, freshwater diatoms, and pollen) also suggests increasing aridity and larger oscillations during the Pliocene and Pleistocene, along with increased intensity of coastal trade winds. Because prominent changes in long-term dust fluxes preceded Northern Hemisphere glaciation by 1.5 Ma, Northern Hemisphere ice sheets were not the major factor in the evolution of African climate, in agreement with late Pleistocene evidence at orbital time scales. The apparent synchroneity of several major long-term changes in climate over Africa and the equatorial Atlantic with changes in the Southern Ocean and South Atlantic suggests long-term linkage in the responses of these two regions, again similar to late Pleistocene linkages at orbital time scales. The ultimate source of forcing of these changes at tectonic time scales is not fully resolved. The Messinian closing and abrupt reopening of the Mediterranean left no obvious imprint on signals of African dust flux. One plausible source of forcing is large-scale tectonic uplift, which occurred at unusually rapid rates during the latest Cenozoic in Southeast Asia (Tibet and the Himalayas), East Africa, and South America (the Andes and Altiplano). Modeling experiments show that uplift causes large-scale rearrangements of atmospheric circulation, including the strength and position of the upper tropospheric jet streams and the lower tropospheric high-and low-pressure cells that control surface winds and moisture balances.

Neogene ocean history is dominated by the theme of stepwise global cooling (with occasional reversals); the main trends of carbonate sedimentation on the Ontong Java Plateau show the regional response of productivity, dissolution, winnowing, and redeposition to this overall climatic change. The relative importance of these processes in controlling accumulation rates and carbonate content is difficult to assess for any given place and time. Thus, the outstanding feature of the carbonate record, the Tortonian-Messinian accumulation rate peak centered in the latest Miocene (maximum sedimentation rate >60 m/m.y.), is the product of a complex interplay of a general late Miocene to early Pliocene productivity maximum combined with increased mechanical and chemical erosion before and after the peak. The mix of erosional factors depends on the depth level considered and changes with time. Increased productivity apparently derives from high nutrient content in Pacific deep waters, caused by increased production of North Atlantic Deep Water (NADW) in the latest Miocene and basin-basin fractionation. Enhancement of the thermocline strength is indicated at that time from an increase in planktonic foraminifers living at intermediate depths. A fundamental change in the mode of productivity (toward pulsed productivity?) is indicated by changes in the coccolith flora.The main focus of this study is the definition of major patterns of sedimentation and associated open questions, as follows:1. Carbonate records are parallel over a wide depth range. Does this mean that dissolution is also important on the upper plateau? Or is there a "conspiracy" of separate factors acting in concert?2. Dissolution of carbonate cannot explain both carbonate and sedimentation rate patterns. The "loss paradox*' arises from the fact that carbonate percentages at different depths are so similar that the differences in carbonate are insufficient to account for differences in sedimentation rate, assuming that dissolution produces these differences.3. Equatorial crossings have little or no effect on carbonate content or sedimentation rate. "Equatorial insensitivity" indicates that equatorial upwelling is of subordinate importance in biogenic sedimentation on the plateau in the late Neogene (as is the case today).4. There is evidence for a general insensitivity of both carbonate and sedimentation rate records with regard to global changes in conditions, as seen in commonly used proxies. Changes in δ 18 θ of benthic foraminifers, for example, and sea-level changes (as mapped by sequence stratigraphy) are not clearly correlated with the main parameters of Neogene carbonate sedimentation on the plateau. Correspondence to the δ 3 C record is somewhat better, however. Proxies may be ill defined, or the regional overprint may obscure global relationships.The issues listed above are of a very general nature. Without a successful attack on these questions, the major patterns of carbonate sedimentation on the plateau will remain enigmatic, as will many phe...

During Ocean Drilling Program Leg 199 a high-resolution (~1-2 cm/ k.y.) biogenic sediment record from the late Paleocene to the early Miocene was recovered, containing an uninterrupted set of geomagnetic chrons as well as a detailed record of calcareous and siliceous biostratigraphic datum events. Shipboard lithologic proxy measurements and shore-based determinations of CaCO 3 revealed regular cycles that can be attributed to climatic forcing. Discovering drill sites with well defined magneto-and biostratigraphic records that also show clear lithologic cycles is rare and valuable and creates the opportunity to develop a detailed stratigraphic intersite correlation, providing the basis to study paleoceanographic processes and mass accumulation rates at high resolution. Here we present extensive postcruise work that extends the shipboard composite depth stratigraphy by providing a high-resolution revised meters composite depth (rmcd) scale to compensate for depth distortion within individual cores. The depth-aligned data were then used to generate stacked records of lithologic proxy measurements. Making use of the increased signal-to-noise ratio in the stacked records, we then proceeded to generate a detailed site-to-site correlation between Sites 1218 and 1219 in order to decrease the depth uncertainty for magnetoand biostratigraphic datums. Stacked lithologic proxy records in combination with discrete measurements of CaCO 3 were then exploited to