Ocean Drilling Program

About: Ocean Drilling Program is a based out in . It is known for research contribution in the topics: Basalt & Oceanic crust. The organization has 235 authors who have published 183 publications receiving 10690 citations. The organization is also known as: ODP.

Distributions of Microbial Activities in Deep Subseafloor Sediments

Abstract: Diverse microbial communities and numerous energy-yielding activities occur in deeply buried sediments of the eastern Pacific Ocean. Distributions of metabolic activities often deviate from the standard model. Rates of activities, cell concentrations, and populations of cultured bacteria vary consistently from one subseafloor environment to another. Net rates of major activities principally rely on electron acceptors and electron donors from the photosynthetic surface world. At open-ocean sites, nitrate and oxygen are supplied to the deepest sedimentary communities through the underlying basaltic aquifer. In turn, these sedimentary communities may supply dissolved electron donors and nutrients to the underlying crustal biosphere.

ODP Leg 107 in the Tyrrhenian Sea: Insights into passive margin and back-arc basin evolution

Abstract: Leg 107 of the Ocean Drilling Program drilled a west-northwest-east-southeast transect of seven sites across the Tyrrhenian Sea, the youngest of the sub-basins of the Mediterranean Sea. Sites 654, 653, 652, and 656 document the rifting and subsidence of the Sardinia passive continental margin. On the upper margin (Site 654), we cored a classic transgressive sequence: subaerial conglomerates, overlain by oyster-bearing sands, overlain by marine marl. Comparison between the recovered lithologies and seismic reflection profiles suggests that the synrift sediments on the upper margin are Tortonian (late Miocene) to Messinian (latest Miocene) in age, whereas synrift sediments on the lower margin are Messinian to Pliocene in age. During the Messinian desiccation of the Mediterranean, Sites 654 and 653, now on the upper Sardinian margin, apparently occupied a basinal setting, where they received nannoplankton-bearing clays interbedded with laminated gypsum. Sites 656 and 652, now on the lower Sardinia margin, were apparently higher standing during the desiccation event; their Messinian facies are subaerial and lacustrine, respectively. We infer from these lines of evidence that tilting and subsidence occurred more than a million years earlier on the upper margin than on the lower margin. Such diachroneity can be interpreted in terms of migration of the zone of maximum extension above a "rolling-back" subduction zone, or in terms of extension of continental crust, by shear along a deep "detachment fault." Sites 655, 651, and 650 were drilled into two small basalt-floored basins of the central and eastern Tyrrhenian. Emplacement of basaltic crust in the central Tyrrhenian (Vavilov Basin) apparently began more than a million years before, emplacement of basaltic crust in the eastern Tyrrhenian (Marsili Basin). This observation is compatible with previous suggestions that the Tyrrhenian has grown southeastward in response to "rollback" of the down-going slab that currently dips northwestward under the toe of Italy. At the easternmost site, high vesicularity of the basalt and benthic foram assemblages in the oldest sediments imply that the basalt erupted in water shallower than 2,500 m. It has apparently subsequently subsided to its present depth of >4,100 m below sea level nearly three times as fast as normal subsidence of crust formed at a mid-ocean ridge.

A Cenozoic record of the equatorial Pacific carbonate compensation depth

Abstract: Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.

Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary

Abstract: The Palaeocene/Eocene thermal maximum — a period of intense global warming about 55 million years ago — was associated with a massive release of isotopically distinctive greenhouse gases into the ocean-atmosphere system. It remains unclear, however, whether this input caused or resulted from the global warming and environmental change that characterize the event. Sluijs et al. use high-resolution records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey to shed light on this question. They find that the onset of environmental change and surface-ocean warming preceded the input of greenhouse gases by several thousand years at this location. This sequence of events is consistent with the proposal that deep-ocean warming caused the dissociation of submarine gas hydrates, releasing massive amounts of the greenhouse gas methane. But the cause of the early warming remains uncertain. Exceptionally high resolution records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey find that the onset of environmental change and surface–ocean warming preceded the input of greenhouse gases by several thousand years. This sequence is consistent with the proposal that warming of the deep ocean caused the dissociation of submarine gas hydrates, which released massive amounts of methane. The start of the Palaeocene/Eocene thermal maximum—a period of exceptional global warming about 55 million years ago—is marked by a prominent negative carbon isotope excursion that reflects a massive input of 13C-depleted (‘light’) carbon to the ocean–atmosphere system1. It is often assumed2 that this carbon injection initiated the rapid increase in global surface temperatures and environmental change that characterize the climate perturbation3,4,5,6,7, but the exact sequence of events remains uncertain. Here we present chemical and biotic records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey that have high sediment accumulation rates. We show that the onsets of environmental change (as recorded by the abundant occurrence (‘acme’) of the dinoflagellate cyst Apectodinium) and of surface-ocean warming (as evidenced by the palaeothermometer TEX86) preceded the light carbon injection by several thousand years. The onset of the Apectodinium acme also precedes the carbon isotope excursion in sections from the southwest Pacific Ocean8 and the North Sea, indicating that the early onset of environmental change was not confined to the New Jersey shelf. The lag of ∼3,000 years between the onset of warming in New Jersey shelf waters and the carbon isotope excursion is consistent with the hypothesis that bottom water warming caused the injection of 13C-depleted carbon by triggering the dissociation of submarine methane hydrates1,9,10, but the cause of the early warming remains uncertain.