Seawater chemistry and hydrothermal controls on the Cenozoic osmium cycle

2021 ◽  
Author(s):  
Joachim A. R. Katchinoff ◽  
Drew D. Syverson ◽  
Noah J. Planavsky ◽  
Erica S. J. Evans ◽  
Alan D. Rooney
Keyword(s):  
Seawater Chemistry

A general model for growth trajectories of linear carbonate platforms

2020 ◽  
Vol 90 (9) ◽  
pp. 1139-1155
Author(s):  
Nicolas Goudemand ◽  
Pulkit Singh ◽  
Jonathan L. Payne
Keyword(s):  
Growth Trajectories ◽  
Carbonate Platforms ◽  
Seawater Chemistry ◽  
Forward Models ◽  
Sedimentary Deposits ◽  
Sediment Production ◽  
Carbonate Sedimentation ◽  
Platform Margin ◽  
Simple Equations ◽  
Analytical Expressions

ABSTRACT A key challenge regarding development of carbonate platforms is predicting the temporal pattern of platform-margin progradation, aggradation, retrogradation, and drowning. Numerical forward models of carbonate sedimentation have been widely applied to this problem, shedding substantial light on the roles of sediment production, transport, tectonic subsidence, and eustasy on the evolution of carbonate platforms. However, forward models are typically complex and computationally expensive, preventing comprehensive exploration of parameter space. In addition, the interactions among parameters are often nonlinear, preventing the development of simple expressions relating the position of the platform margin to the governing parameters of the model. To complement the considerable insights derived from numerical forward models, this study presents analytical expressions for the temporal evolution of the position of platform margins using the simplest possible assumptions regarding sediment production and transport. These expressions provide useful null models, deviations from which can be used to identify the particular effects of biology or seawater chemistry on carbonate factories in influencing the development of these important sedimentary deposits. Application of the model to synthetic and outcrop examples demonstrates that these simple equations are useful for parameter estimation that can then be used to guide more detailed, process-based numerical forward models.

scholarly journals Ba incorporation in benthic foraminifera

2017 ◽  
Author(s):  
Lennart J. de Nooijer ◽  
Anieke Brombacher ◽  
Antje Mewes ◽  
Gerald Langer ◽  
Gernot Nehrke ◽  
...  
Keyword(s):  
Trace Elements ◽  
Benthic Foraminifera ◽  
General Trend ◽  
Seawater Chemistry ◽  
Minor And Trace Elements ◽  
Foraminiferal Species ◽  
Element Partitioning ◽  
The Difference ◽  
Species Specific ◽  
New Applications

Abstract. Barium (Ba) incorporated in the calcite of many foraminiferal species is proportional to the concentration of Ba in seawater. Since the open ocean concentration of Ba closely follows seawater alkalinity, foraminiferal Ba/Ca can be used to reconstruct the latter. Alternatively, Ba/Ca from foraminiferal shells can also be used to reconstruct salinity in coastal settings where seawater Ba concentration corresponds to salinity as rivers contain much more Ba than seawater. Incorporation of a number of minor and trace elements is known to vary (greatly) between foraminiferal species and application of element/Ca ratios thus requires the use of species-specific calibrations. Here we show that calcite Ba/Ca correlates positively and linearly with seawater Ba/Ca in cultured specimens of two species of benthic foraminifera, Heterostegina depressa and Amphistegina lessonii. The slopes of the regression, however, vary 2–3 fold between these two species (0.33 and 0.78, respectively). This difference in Ba-partitioning resembles the difference in partitioning of other elements (Mg, Sr, B, Li and Na) in these foraminiferal taxa. A general trend across element partitioning for different species is described, which may help developing new applications of trace elements in foraminiferal calcite in reconstructing past seawater chemistry.

scholarly journals Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean

2020 ◽  
Vol 117 (36) ◽  
pp. 22281-22292 ◽  
Author(s):  
Mario Lebrato ◽  
Dieter Garbe-Schönberg ◽  
Marius N. Müller ◽  
Sonia Blanco-Ameijeiras ◽  
Richard A. Feely ◽  
...  
Keyword(s):  
International Association ◽  
Open Ocean ◽  
Total Alkalinity ◽  
Polar Regions ◽  
Marine Environments ◽  
Physical Sciences ◽  
Seawater Chemistry ◽  
Sr:Ca Ratios ◽  
Biogeochemical Parameters ◽  
Dynamic Exchange

Seawater Mg:Ca and Sr:Ca ratios are biogeochemical parameters reflecting the Earth–ocean–atmosphere dynamic exchange of elements. The ratios’ dependence on the environment and organisms' biology facilitates their application in marine sciences. Here, we present a measured single-laboratory dataset, combined with previous data, to test the assumption of limited seawater Mg:Ca and Sr:Ca variability across marine environments globally. High variability was found in open-ocean upwelling and polar regions, shelves/neritic and river-influenced areas, where seawater Mg:Ca and Sr:Ca ratios range from ∼4.40 to 6.40 mmol:mol and ∼6.95 to 9.80 mmol:mol, respectively. Open-ocean seawater Mg:Ca is semiconservative (∼4.90 to 5.30 mol:mol), while Sr:Ca is more variable and nonconservative (∼7.70 to 8.80 mmol:mol); both ratios are nonconservative in coastal seas. Further, the Ca, Mg, and Sr elemental fluxes are connected to large total alkalinity deviations from International Association for the Physical Sciences of the Oceans (IAPSO) standard values. Because there is significant modern seawater Mg:Ca and Sr:Ca ratios variability across marine environments we cannot absolutely assume that fossil archives using taxa-specific proxies reflect true global seawater chemistry but rather taxa- and process-specific ecosystem variations, reflecting regional conditions. This variability could reconcile secular seawater Mg:Ca and Sr:Ca ratio reconstructions using different taxa and techniques by assuming an error of 1 to 1.50 mol:mol, and 1 to 1.90 mmol:mol, respectively. The modern ratios’ variability is similar to the reconstructed rise over 20 Ma (Neogene Period), nurturing the question of seminonconservative behavior of Ca, Mg, and Sr over modern Earth geological history with an overlooked environmental effect.

Mesozooplankton community in a seasonally hypoxic and highly eutrophic bay

2015 ◽  
Vol 66 (8) ◽  
pp. 719 ◽  
Author(s):  
Min-Chul Jang ◽  
Kyoungsoon Shin ◽  
Pung-Guk Jang ◽  
Woo-Jin Lee ◽  
Keun-Hyung Choi
Keyword(s):  
High Temperature ◽  
Bottom Water ◽  
Oxygen Solubility ◽  
Low Oxygen ◽  
Negative Effects ◽  
Mesozooplankton Community ◽  
Seawater Chemistry ◽  
Hypoxic Conditions ◽  
Bottom Waters ◽  
Major Factors

A 2-year survey of seawater chemistry and mesozooplankton abundance was carried out in Masan Bay, South Korea, one of the most eutrophic coastal ecosystems known. The study aimed to identify the major factors contributing to the seasonally persistent hypoxia in the bay, to characterise the Bay’s mesozooplankton community and to examine the effects of low oxygen on the distribution of mesozooplankton. Hypoxia (<2mgO2L–1) was present only in summer, with ultrahypoxia (<0.2mg O2 L–1) in the bottom waters of the inner bay in both years. Low summer oxygen can be attributed to high summer phytoplankton stocks, together with reduced oxygen solubility at high temperature and stratification of the water column that limits downward diffusion of oxygen. A seasonally and spatially distinct mesozooplankton community was identified in summer when there was greater influence of freshwater discharge in the inner bay. Marine cladocerans were very abundant, with a population outburst of Penilia avirostris in the inner bay (>4000 individuals m–3) during summer. During hypoxic events, the abundance of Penilia avirostris was positively related to oxygen levels in the bottom water, suggesting that hypoxic conditions may cause mortality or have sublethal negative effects on population growth of this filter-feeding cladoceran.

A 12-Million-Year Temperature History of the Tropical Pacific Ocean

Science ◽  
2014 ◽  
Vol 344 (6179) ◽  
pp. 84-87 ◽  
Author(s):  
Yi Ge Zhang ◽  
Mark Pagani ◽  
Zhonghui Liu
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Sea Surface ◽  
Temperature History ◽  
Seawater Chemistry ◽  
The Pacific ◽  
Pacific Warm Pool ◽  
History Of ◽  
The Tropical Pacific

The appearance of permanent El Niño–like conditions prior to 3 million years ago is founded on sea-surface temperature (SST) reconstructions that show invariant Pacific warm pool temperatures and negligible equatorial zonal temperature gradients. However, only a few SST records are available, and these are potentially compromised by changes in seawater chemistry, diagenesis, and calibration limitations. For this study, we establish new biomarker-SST records and show that the Pacific warm pool was ~4°C warmer 12 million years ago. Both the warm pool and cold tongue slowly cooled toward modern conditions while maintaining a zonal temperature gradient of ~3°C in the late Miocene, which increased during the Plio-Pleistocene. Our results contrast with previous temperature reconstructions that support the supposition of a permanent El Niño–like state.

Sign in / Sign up

Export Citation Format

Share Document