Antarctic icebergs reorganize ocean circulation during Pleistocene glacials
"The dominant feature of large-scale mass transfer in the modern ocean is the Atlantic meridional overturning circulation (AMOC). The geometry and vigour of this circulation influences global climate on various timescales. Palaeoceanographic evidence suggests that during glacial periods of the past 1.5 million years the AMOC had markedly different features from today1; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled2. An absence of evidence on the origin of this phenomenon means that the sequence of events leading to global glacial conditions remains unclear.[...]"
Authors: Aidan Starr et al.
The role of calcium in regulating marine phosphorus burial and atmospheric oxygen
"The marine phosphorus cycle plays a critical role in controlling the extent of global primary productivity and thus atmospheric pO2 on geologic time scales. However, previous attempts to model carbon–phosphorus-oxygen feedbacks have neglected key parameters that could shape the global P cycle. Here we present new diagenetic models to fully parameterize marine P burial. We have also coupled this diagenetic framework to a global carbon cycle model. We find that seawater calcium concentration, by strongly influencing carbonate fluorapatite (CFA) formation, is a key factor controlling global phosphorus cycling, and therefore plays[...]"
Source: Nature Communications
Authors: Mingyu Zhao et al.
Response of the western proto-North Atlantic margin to the early Aptian Oceanic Anoxic Event (OAE) 1a: an example from the Cupido platform margin
-Gulf of Mexico, NE Mexico
"Integrated microfacies and geochemical analyses conducted on five stratigraphic sections in northeastern Mexico (ancentral western margin of the proto-North Atlantic) reveal major paleoenvironmental changes in shallow water and pelagic environments in the prelude and run-up of the early Aptian oceanic anoxic event (OAE) 1a. During the Barremian–Aptian transition, the replacement of photozoan rudist-coral by mesotrophic/eutrophic orbitolinid-miliolid communities in the Cupido platform occurred in association with increased nutrient input. [...]"
Source: Cretaceous Research
Authors: Fernando Núñez-Useche et al.
Warm afterglow from the Toarcian Oceanic Anoxic Event drives the success of deep-adapted brachiopods
"Many aspects of the supposed hyperthermal Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic, c. 182 Ma) are well understood but a lack of robust palaeotemperature data severely limits reconstruction of the processes that drove the T-OAE and associated environmental and biotic changes. New oxygen isotope data from calcite shells of the benthic fauna suggest that bottom water temperatures in the western Tethys were elevated by c. 3.5 °C through the entire T-OAE. [...]"
Source: Scientific Reports
Auhtors: C. V. Ullmann et al.
High Resolution Osmium Data Record Three Distinct Pulses of Magmatic Activity During Cretaceous Oceanic Anoxic Event 2 (OAE-2)
"Oceanic anoxic Event 2 (OAE-2) occurred at the Cenomanian-Turonian boundary (∼94.1 Ma) and was a time of profound global changes in ocean chemistry and the carbon cycle. This event was characterized by a positive carbon isotope excursion (CIE) caused by massive organic carbon burial, global greenhouse temperatures, ocean deoxygenation, and changes in ocean life driven by large igneous province (LIP) activity. LIPS throughout the Phanerozoic have had dynamic magma flux, with episodes of major eruptions interspersed with periods of relatively less intense eruptions. [...]"
Source: Geochimica et Cosmochimica Acta
Authors: Daniel L. Sullivan et al.
Fe isotope composition of Archean sulfides do not record progressive oxygenation of the ocean
"In the history of this continuously evolving planet, the Great Oxygenation Event (GOE), which occurred at ca. 2.3 Ga (Bekker et al., 2004; Holland, 2006) was a critical environmental change. This event was first recognized by the disappearance of detrital uraninite, pyrite, and siderite, from the siliciclastic record, as well as by shales that do not contain appreciable amounts of redox-sensitive elements and paleosols that are not oxidized before ca. 2.3 Ga (Holland, 2006). [...]"
Authors: Johanna Marin Carbonne
Associations between redox‐sensitive trace metals and microbial communities in a Proterozoic ocean analogue
"Constraints on Precambrian ocean chemistry are dependent upon sediment geochemistry. However, diagenesis and metamorphism can destroy primary biosignatures, making it difficult to consider biology when interpreting geochemical data. Modern analogues for ancient ecosystems can be useful tools for identifying how sediment geochemistry records an active biosphere. The Middle Island Sinkhole (MIS) in Lake Huron is an analogue for shallow Proterozoic waters due to its low oxygen water chemistry and microbial communities that exhibit diverse metabolic functions at the sediment–water interface. [...]"
Authors: Kathryn I. Rico
Temperature-related body size change of marine benthic macroinvertebrates across the Early Toarcian Anoxic Event
"The Toarcian Oceanic Anoxic Event (TOAE, Early Jurassic, ~182 Ma ago) was characterised by severe environmental perturbations which led to habitat degradation and extinction of marine species. Warming-induced anoxia is usually identified as main driver, but because marine life was also affected in oxygenated environments the role of raised temperature and its effects on marine life need to be addressed. [...]"
Source: Scientific Reports
Authors: Veronica Piazza et al.
Phosphorus-limited conditions in the early Neoproterozoic ocean maintained low levels of atmospheric oxygen
"The redox chemistry of anoxic continental margin settings evolved from widespread sulfide-containing (euxinic) conditions to a global ferruginous (iron-containing) state in the early Neoproterozoic era (from ~1 to 0.8 billion years ago). Ocean redox chemistry exerts a strong control on the biogeochemical cycling of phosphorus, a limiting nutrient, and hence on primary production, but the response of the phosphorus cycle to this major ocean redox transition has not been investigated. [...]"
Source: Nature Geoscience
Authors: Romain Guilbaud et al.
Neritic ecosystem response to Oceanic Anoxic Event 2 in the Cretaceous Western Interior Seaway, USA
"Cretaceous oceanic anoxic events (OAEs) were periods of geologically short (<1 million years) global change characterized by elevated temperatures, changes in ocean biogeochemistry, ecological turnover, and the global-scale deposition of black shales. After decades of OAE research, the intensity and spatiotemporal heterogeneity of ocean anoxia and its direct effects on marine ecology remain areas of active study. We present high-resolution organic geochemical and foraminiferal records from the western margin of the Western Interior Seaway (WIS) during the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2, ~94 Ma) that indicate reorganization of a neritic ecosystem in response to sea-level rise, and dynamic changes in redox conditions that were likely driven by enhanced marine productivity. [...]"
Source: Palaeogeography, Palaeoclimatology, Palaeoecology
Authors: F. Garrett Boudinot et al.