News

The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development

Abstract.

"Despite their name, Oceanic Anoxic Events (OAEs) are not periods of uniform anoxia and black shale deposition in ancient oceans. Shelf environments account for the majority of productivity and organic carbon burial in the modern ocean, and this was likely true in the Cretaceous as well. However, it is unlikely that the mechanisms for such an increase were uniform across all shelf environments. Some, like the northwest margin of Africa, were characterized by strong upwelling, but what might drive enhanced productivity on shelves not geographically suited for upwelling? [...]"

Source: Plaeoceanography
Authors: Christopher M. Lowery
DOI: 10.1002/2017PA003180

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Repeated storage of respired carbon in the equatorial Pacific Ocean over the last three glacial cycles

Abstract.

"As the largest reservoir of carbon exchanging with the atmosphere on glacial–interglacial timescales, the deep ocean has been implicated as the likely location of carbon sequestration during Pleistocene glaciations. Despite strong theoretical underpinning for this expectation, radiocarbon data on watermass ventilation ages conflict, and proxy interpretations disagree about the depth, origin and even existence of the respired carbon pool. [...]"

Authors: A.W. Jacobel
Source: Nature Communications
DOI: 10.1038/s41467-017-01938-x

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Oxygenation as a driver of the Great Ordovician Biodiversification Event

Abstract.

"The largest radiation of Phanerozoic marine animal life quadrupled genus-level diversity towards the end of the Ordovician Period about 450 million years ago. A leading hypothesis for this Great Ordovician Biodiversification Event is that cooling of the Ordovician climate lowered sea surface temperatures into the thermal tolerance window of many animal groups, such as corals. [...]"

Source: Nature Geoscience
Authors: Cole T. Edwards
DOI: 10.1038/s41561-017-0006-3

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When oxygen disappeared, early marine animals really started evolving

"Animals need oxygen to survive, but a relative lack of oxygen in Earth’s ancient oceans helped early marine creatures evolve, a new study claims. Indeed, the “Cambrian explosion”—the burst of evolution about 540 million years ago that included the birth of most of the major animal groups we know today—was enabled by oxygen deprivation, the researchers say. The finding comes in the wake of a better understanding of how oxygen levels in the oceans and the atmosphere fluctuated in the deep past, and may shift how scientists think animal evolution can proceed. [...]"

Source: Science Magazine
Author: Lucas Joel
DOI: 10.1126/science.aar5252

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Abyssal ocean overturning shaped by seafloor distribution

Abstract.

"The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less-dense waters above them. Understanding what controls the strength and structure of these interhemispheric flows—referred to as the abyssal overturning circulation—is key to quantifying the ocean’s ability to store carbon and heat on timescales exceeding a century. [...]"

Source: Nature
Authors: C. de Lavergne et al.
DOI: 10.1038/nature24472

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The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development

Abstract.

"Despite their name, Oceanic Anoxic Events (OAEs) are not periods of uniform anoxia and black shale deposition in ancient oceans. Shelf environments account for the majority of productivity and organic carbon burial in the modern ocean, and this was likely true in the Cretaceous as well. However, it is unlikely that the mechanisms for such an increase were uniform across all shelf environments. [...]"

Source: Paleoceanography
Authors: Christopher M. Lowery
DOI: 10.1002/2017PA003180

Read the full article here.


A molybdenum-isotope perspective on Phanerozoic deoxygenation events

Abstract.

"The expansion and contraction of sulfidic depositional conditions in the oceans can be tracked with the isotopic composition of molybdenum in marine sediments. However, molybdenum-isotope data are often subject to multiple conflicting interpretations. Here I present a compilation of molybdenum-isotope data from three time intervals: the Toarcian Oceanic Anoxic Event about 183 million years ago, Oceanic Anoxic Event 2 about 94 million years ago, and two early Eocene hyperthermal events from 56 to 54 million years ago. [...]"

Source: Nature Geoscience
Authors: Alexander J. Dickson
DOI: 10.1038/ngeo3028

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