We present evidence for Antarctic Circumpolar Current (ACC)-like effects on Atlantic deepwater circulation beginning in the late-middle Eocene. Modern ocean circulation is characterized by a thermal differentiation between Southern Ocean and North Atlantic deepwater formation regions. In order to better constrain the timing and nature of the initial thermal differentiation between Northern Component Water (NCW) and Southern Component Water (SCW), we analyze benthic foraminiferal stable isotope (O-18(bf) and C-13(bf)) records from Ocean Drilling Program Site 1053 (upper deep water, western North Atlantic). Our data, compared with published records and interpreted in the context of ocean circulation models, indicate that progressive opening of Southern Ocean gateways and initiation of a circum-Antarctic current caused a transition to a modern-like deep ocean circulation characterized by thermal differentiation between SCW and NCW beginning similar to 38.5Ma, in the initial stages of Drake Passage opening. In addition, the relatively low O-18(bf) values recorded at Site 1053 show that the cooling trend of the middle-late Eocene was not global, because it was not recorded in the North Atlantic. The timing of thermal differentiation shows that NCW contributed to ocean circulation by the late-middle Eocene, similar to 1-4Myr earlier than previously thought. We propose that early NCW originated in the Labrador Sea, based on tectonic reconstructions and changes in foraminiferal assemblages in this basin. Finally, we link further development of meridional isotopic gradients in the Atlantic and Pacific in the late Eocene with the Tasman Gateway deepening (similar to 34Ma) and the consequent development of a circumpolar proto-ACC.

We obtained global sea-level (eustatic) estimates with a peak of similar to 22 m higher than present for the Pliocene interval 2.7-3.2 Ma from backstripping in Virginia (United States), New Zealand, and Enewetak Atoll (north Pacific Ocean), benthic foraminiferal delta O-18 values, and Mg/Ca-delta O-18 estimates. Statistical analysis indicates that it is likely (68% confidence interval) that peak sea level was 22 +/- 5 m higher than modern, and extremely likely (95%) that it was 22 +/- 10 m higher than modern. Benthic foraminiferal delta O-18 values appear to require that the peak was <20-21 m. Our estimates imply loss of the equivalent of the Greenland and West Antarctic ice sheets, and some volume loss from the East Antarctic Ice Sheet, and address the long-standing controversy concerning the Pliocene stability of the East Antarctic Ice Sheet.

I report magnetic susceptibility point measurements on the lower Maastrichtian–lowermost Eocene section retrieved in a core taken near the GSSP for the Paleocene/Eocene boundary in the Dababiya Quarry (Upper Nile Valley, Egypt). This record of magnetic susceptibility supplements the visual core descriptions, with lower values corresponding to more calcareous intervals. Preliminary investigation suggests that cyclicity apparent in the magnetic susceptibility record is consistent with a response to variations in Earth’s orbital eccentricity. This interpretation is consistent with biostratigraphy and would imply sedimentation rates varying in the range 6–11m/Myr, with lower sedimentation rates associated with intervals of low susceptibility/high carbonate.

We reconstruct trends in ice volume and deep ocean temperature for the past 108 Myr, resolving variations on timescales of similar to 2 Myr and longer. We use a sea level record as a proxy for ice volume, a benthic foraminiferal Mg/Ca-bf record as a proxy for temperature, and a benthic foraminiferal d(18)O(bf) record as a proxy for both. This allows us to construct dual estimates of temperature and ice volume variations for the interval 10-60 Ma: extracting temperature from d(18)O(bf) by using sea level as a proxy for ice volume to constrain the d(18)O(sw) component, and extracting seawater d(18)O(sw) (which reflects ice volume) from d(18)O(bf) by using Mg/Ca-bf to constrain the temperature component. Each of these approaches requires numerous assumptions, but the range of plausible solutions are concordant on timescales >2 Myr and within an uncertainty of +/- 2 degrees C temperature and +/- 0.4 parts per thousand delta O-18(sw). The agreement between the two approaches for the last 50 Myr provides empirical justification for the use of d(18)O(bf), Mg/Ca-bf, and sea level records as robust climate proxies. Our reconstructions indicate differences between deep ocean cooling and continental ice growth in the late Cenozoic: cooling occurred gradually in the middle-late Eocene and late Miocene-Pliocene while ice growth occurred rapidly in the earliest Oligocene, middle Miocene, and Plio-Pleistocene. These differences are consistent with climate models that imply that temperatures, set by the long-term CO2 equilibrium, should change only gradually on timescales >2 Myr, but growth of continental ice sheets may be rapid in response to climate thresholds due to feedbacks that are not yet fully understood.

Global cooling and the development of continental-scale Antarctic glaciation occurred in the late middle Eocene to early Oligocene (~38 to 28 million years ago), accompanied by deep-ocean reorganization attributed to gradual Antarctic Circumpolar Current (ACC) development. Our benthic foraminiferal stable isotope comparisons show that a large δ(13)C offset developed between mid-depth (~600 meters) and deep (>1000 meters) western North Atlantic waters in the early Oligocene, indicating the development of intermediate-depth δ(13)C and O(2) minima closely linked in the modern ocean to northward incursion of Antarctic Intermediate Water. At the same time, the ocean's coldest waters became restricted to south of the ACC, probably forming a bottom-ocean layer, as in the modern ocean. We show that the modern four-layer ocean structure (surface, intermediate, deep, and bottom waters) developed during the early Oligocene as a consequence of the ACC.

Geochemical analyses of the carbonate tests calcified by foraminifera have provided much of the foundation for reconstructions of past ocean and climate conditions, and for chemostratigraphy. In particular, reconstructions of climate history (including temperature, salinity, and ice volume), ocean paleocirculation patterns, the carbon cycle, paleoproductivity, marine carbonate chemistry, and chemostratigraphy have relied on measurements of isotopic and trace element composition of foraminiferal calcium carbonate, and variations in these geochemical records through time and space. Substantial work has been done on details of traditional proxies (e.g., delta O-18, delta C-13) and on emerging proxies (e.g., delta B-11, epsilon(Nd)) in recent years; hence, a new overview of these proxies provides a timely reference and educational tool. We review the geochemical proxies that utilize foraminiferal carbonate tests, including potential uses of the proxies for reconstructions through time: delta O-18, delta C-13, trace elements (Mg, Cd, Ba, Zn, B, U), Sr-87/Sr-86, delta Mg-26, delta B-11, and epsilon(Nd). Both planktic and benthic foraminifera are included; planktic foraminifera provide information on the upper few hundred meters of the surface ocean, whereas benthic foraminifera provide information on conditions at the seafloor and in shallow porewaters, from shallow seas to deep ocean basins.

We describe seven Paleocene to lowermost Eocene sequences in core holes at Island Beach, Bass River, Ancora, Millville, and Sea Girt, NJ (Ocean Drilling Program Leg 150X, 174AX) and analyze benthic foraminiferal assemblages to assess paleodepth changes within sequences. These sequences are referred to as Pa0, Pa1a, Pa1b, Pa2a, Pa2b, Pa3a, and Pa3b. Paleocene sequence boundaries are identified by unconformities and variations in benthic foraminiferal biofacies. We used Q-mode factor analysis and paleoslope modeling to identify three distinct middle-outer neritic benthic foraminiferal assemblages and their associated water depths. Paleodepths during the early Paleocene and deposition of Pa0, Pa1a, and Pa2b were similar to 80 m with similar to 20 m changes across sequence boundaries. A long-term shallowing occurred through the late Paleocene where paleodepths were similar to 50-70 m in Pa3a. This trend drastically changes in the earliest Eocene where the paleodepths of sequence Pa3b were similar to 120-150 m. New Jersey Paleocene sequence boundaries correlate with those in other regions and with delta O-18 increases in the deep sea, suggesting Paleocene eustatic lowerings were associated with ice-growth events.

We present an overview of the Eocene-Oligocene transition from a marine perspective and posit that growth of a continent-scale Antarctic ice sheet (25 x 10(6) km(3)) was a primary cause of a dramatic reorganization of ocean circulation and chemistry. The Eocene-Oligocene transition (EOT) was the culmination of long-term (10(7) yr scale) CO2 drawdown and related cooling that triggered a 0.5%-0.9% transient precursor benthic foraminiferal delta O-18 increase at 33.80 Ma (EOT-1), a 0.8% delta O-18 increase at 33.63 Ma (EOT-2), and a 1.0% delta O-18 increase at 33.55 Ma ( oxygen isotope event Oi-1). We show that a small (similar to 25 m) sea-level lowering was associated with the precursor EOT-1 increase, suggesting that the delta O-18 increase primarily reflected 1-2 degrees C of cooling. Global sea level dropped by 80 +/- 25 m at Oi-1 time, implying that the deep-sea foraminiferal delta O-18 increase was due to the growth of a continent-sized Antarctic ice sheet and 1-4 degrees C of cooling. The Antarctic ice sheet reached the coastline for the first time at ca. 33.6 Ma and became a driver of Antarctic circulation, which in turn affected global climate, causing increased latitudinal thermal gradients and a "spinning up" of the oceans that resulted in: (1) increased thermohaline circulation and erosional pulses of Northern Component Water and Antarctic Bottom Water; (2) increased deep-basin ventilation, which caused a decrease in oceanic residence time, a decrease in deep-ocean acidity, and a deepening of the calcite compensation depth (CCD); and (3) increased diatom diversity due to intensified upwelling.

We evaluated the age of two Upper Eocene impact ejecta layers (North American microtektites linked to the Chesapeake Bay impact structure and clinopyroxene [cpx] spherules from the Popigai crater) and the global effects of the associated impact events. The reported occurrence of cpx spherules from the Popigai impact structure at South Atlantic ODP Site 1090 within the middle of magnetochron C16n.1n yields a magnetochronologic age of 35.4 Ma. We generated high-resolution stable isotope records at Sites 1090, 612 (New Jersey slope), and Caribbean core RC9-58 that show: (1) a 0.5% delta C-13 decrease in bulk-carbonate at Site 1090 coincident with the Popigai cpx spherule layer, and (2) a 0.4%-0.5% decrease in deep-water benthic for aminiferal delta C-13 values across the Popigai impact ejecta layer at Site 612 and core RC9-58. We conclude that the delta C-13 excursion associated with Popigai was a global event throughout the marine realm that can be correlated to magnetochron C16n.1n. The amplitude of this excursion (similar to 0.5%) is within the limits of natural variability, suggesting it was caused by a decrease in carbon export productivity, potentially triggered by the impact event(s). North American microtektites associated with the Chesapeake Bay impact occur stratigraphically above the Popigai cpx spherules at Site 612 and core RC9-58. We found no definite evidence of a delta C-13 anomaly associated with the North American microtektite layer, though further studies are warranted. High-resolution bulk-carbonate and benthic foraminiferal delta O-18 records show no global temperature change associated with the cpx spherule or North American microtektite layers.

[1] Benthic foraminiferal oxygen isotopic (d 18 O) and carbon isotopic (d 13 C) trends, constructed from compilations of data series from multiple ocean sites, provide one of the primary means of reconstructing changes in the ocean interior. These records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records. We present new benthic foraminiferal d 18 O and d 13 C compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to � 80Ma andtentatively to � 110Ma. First-order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the Late Cretaceous (>� 65 Ma) to early Paleogene (35– 65 Ma) homogeneity and a return to heterogeneity in the late Paleogene–early Neogene (35–0 Ma). We propose that these transitions reflect alterations in a first-order characteristic of ocean circulation: the ability of winds to make water in the deep ocean circulate. We document the initiation of large interbasinal d 18 O gradients in the early Oligocene and link the variations in interbasinal d 18 O gradients from the middle Eocene to Oligocene with the increasing influence of wind-driven mixing due to the gradual tectonic opening of Southern Ocean passages and initiation and strengthening of the Antarctic Circumpolar Current. The role of wind-driven upwelling, possibly associated with a Tethyan Circumequatorial Current, in controlling Late Cretaceous interior ocean heterogeneity should be the subject of further research.

We assembled and dated a late Pleistocene sea-level record based on sequence stratigraphy from the New Jersey margin and compared it with published records from fossil uplifted coral reefs in New Guinea, Barbados, and Araki Island, as well as a composite sea-level estimate from scaling of Red Sea isotopic values. Radiocarbon dates, amino acid racemization data, and superposition constrain the ages of large (20-80 m) sea-level falls from New Jersey that correlate with Marine Isotope Chrons (MIC) 2, 3b, 4, 5b, and 6 (the past 130 kyr). The sea-level records for MIC 1, 2, 4, 5e, and 6 are similar to those reported from New Guinea, Barbados, Araki, and the Red Sea; some differences exist among records for MIC 3. Our record consistently provides the shallowest sea level estimates for MIC3 (similar to 25-60 m below present): it agrees most closely with the New Guinea record of Chappell (2002; similar to 35-70 m), but contrasts with deeper estimates provided by Araki (similar to 85-95 m) and the Red Sea (50-90 m). Comparison of eustatic estimates with benthic foraminiferal delta O-18 records shows that the deep sea cooled similar to 2.5 degrees C between MIC 5e and 5d (similar to 120-110 ka) and that near freezing conditions persisted until Termination la (14-15 ka). Sea-level variations between MIC 5b and 2 (ca. 90-20 ka) follow a well-accepted 0.1 parts per thousand/10 m linear variation predicted by ice-growth effects on foraminiferal delta O-18 values. The pattern of deep-sea cooling follows a previously established hysteresis loop between two stable modes of operation. Cold, near freezing deep-water conditions characterize most of the past 130 kyr punctuated only by two warm intervals (the Holocene/MIC 1 and MIC 5e). We link these variations to changes in Northern Component Water (NCW). (C) 2009 Elsevier B.V. All rights reserved.