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‰ δ 13 C 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 foraminiferal δ 13 C values across the Popigai impact ejecta layer at Site 612 and core RC9-58. We conclude that the δ 13 C 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 (~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 δ 13 C anomaly associated with the North American microtektite layer, though further studies are warranted. High-resolution bulk-carbonate and benthic foraminiferal δ 18 O records show no global temperature change associated with the cpx spherule or North American microtektite layers.

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 × 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 drawdown and related cooling that triggered a 0.5‰–0.9‰ transient pre-scale) CO 2 cursor benthic foraminiferal δ 18 O increase at 33.80 Ma (EOT-1), a 0.8‰ δ 18 O increase at 33.63 Ma (EOT-2), and a 1.0‰ δ 18 O increase at 33.55 Ma (oxygen isotope event Oi-1). We show that a small (~25 m) sea-level lowering was associated with the precursor EOT-1 increase, suggesting that the δ 18 O increase primarily reflected 1–2 °C of cooling. Global sea level dropped by 80 ± 25 m at Oi-1 time, implying that the deep-sea foraminiferal δ 18 O increase was due to the growth of a continent-sized Antarctic ice sheet and 1–4 °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.

The Eyreville core holes provide the first continuously cored record of postimpact sequences from within the deepest part of the central Chesapeake Bay impact crater. We analyzed the upper Eocene to Pliocene postimpact sediments from the Eyreville A and C core holes for lithology (semiquantitative measurements of grain size and composition), sequence stratigraphy, and chronostratigraphy. Age is based primarily on Sr isotope stratigraphy supplemented by biostratigraphy (dinocysts, nannofossils, and planktonic foraminifers); age resolution is approximately ±0.5 Ma for early Miocene sequences and approximately ±1.0 Ma for younger and older sequences. Eocene–lower Miocene sequences are subtle, upper middle to lower upper Miocene sequences are more clearly distinguished, and upper Miocene–Pliocene sequences display a distinct facies pattern within sequences. We recognize two upper Eocene, two Oligocene, nine Miocene, three Pliocene, and one Pleistocene sequence and correlate them with those in New Jersey and Delaware. The upper Eocene through Pleistocene strata at Eyreville record changes from: (1) rapidly deposited, extremely fine-grained Eocene strata that probably represent two sequences deposited in a deep (>200 m) basin; to (2) highly dissected Oligocene (two very thin sequences) to lower Miocene (three thin sequences) with a long hiatus; to (3) a thick, rapidly deposited (43–73 m/Ma), very fine-grained, biosiliceous middle Miocene (16.5–14 Ma) section divided into three sequences (V5–V3) deposited in middle neritic paleoenvironments; to (4) a 4.5-Ma-long hiatus (12.8–8.3 Ma); to (5) sandy, shelly upper Miocene to Pliocene strata (8.3–2.0 Ma) divided into six sequences deposited in shelf and shoreface environments; and, last, to (6) a sandy middle Pleistocene paralic sequence (~400 ka). The Eyreville cores thus record the filling of a deep impact-generated basin where the timing of sequence boundaries is heavily influenced by eustasy.

Abstract Understanding eustatic (global sea-level) changes and their effects on the geological record is an important but difficult task because eustatic effects are complexly intertwined with basin subsidence and changes in sediment supply. Led by Peter Vail, researchers at EPR reconstructed a eustatic history by applying sequence stratigraphy to a global array of proprietary seismic profiles, industry wells, and outcrops. This EPR eustatic record has been controversial owing to methodological concerns and reliance on largely unpublished data. The Ocean Drilling Program (ODP) has focussed on drilling the New Jersey, Bahamas, and Australian margins for sea-level studies and has accomplished the following: Validated a transect approach of drilling passive continental margins and carbonate platforms (onshore, shelf, slope); Tested and validated the assumption that the primary cause of impedance contrasts producing seismic reflections on continental margins are stratal surfaces including unconformities; Proved that the ages of sequence boundaries on margins can be determined to better than ±0.5 m.y. and provided a chronology of eustatic lowering for the past 100 m.y.; Achieved orbital-scale (perhaps suborbital) stratigraphic resolution on continental slopes and carbonate platforms; Showed that siliciclastic and carbonate margins yield correlatable and in some cases comparable records of sea-level change; Evaluated the sedimentary response of both tropical and cool-water carbonate platforms to eustatic changes; Begun to constrain the amplitude and cause of eustatic change for both the Iceahouse World of the past 42 m.y. and the Greenhouse World of 250-42 Ma, as outlined below.

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