scholarly journals Benthic Foraminifera from Middle to Late Pleistocene, coastal upwelling sediments of ODP Hole 686B, Pacific Ocean, off Peru

1991 ◽  
Vol 9 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Kathryn A. Malmgren ◽  
Brian M. Funnell
Keyword(s):  
Late Pleistocene ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Water Oxygen ◽  
Minimum Zone ◽  
Water Depths ◽  
Oxygen Minimum

Abstract. Benthic Foraminifera from middle to late Pleistocene, (c. 600ka to 0ka), sediments of ODP Hole 686B, off Peru, show highest abundances and diversities during periods of cooler surface waters, (inferred from the Uk37 index), and enhanced upwelling, (inferred from the peridinacean/gonyaulacacean dinoflagellate cyst ratio). During the latest Pleistocene, (c. 160ka to 0ka), these periods are characterised by higher organic carbon contents in the bottom sediments, and occur during the odd-numbered, interglacial_18O stages. The benthic Foraminifera indicate deposition in 120 to 250 metres water depth for the earlier part of the record, (c. 600ka to c. 200ka), within the oxygen-minimum zone, with bottom water oxygen contents of <0.5 to 0.2 ml/l, (inferred from the dominance of Bolivinellina humilis). Deposition in water depths approaching those of the present day, (c. 450 metres), is indicated from c. 160ka onwards, with better oxygenated bottom water conditions, probably corresponding to the lower part of the oxygen-minimum zone.

Effects of bottom water oxygen concentrations on mercury distribution and speciation in sediments below the oxygen minimum zone of the Arabian Sea

2016 ◽  
Vol 186 ◽  
pp. 24-32 ◽  
Author(s):  
Parthasarathi Chakraborty ◽  
Robert P. Mason ◽  
Saranya Jayachandran ◽  
Krushna Vudamala ◽  
Kazip Armoury ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Bottom Water ◽  
Oxygen Minimum Zone ◽  
Mercury Distribution ◽  
Water Oxygen ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

scholarly journals Differences between coastal and open ocean distributions of N<sub>2</sub>O in the oxygen minimum zone off Peru

2015 ◽  
Vol 12 (13) ◽  
pp. 10167-10193 ◽  
Author(s):  
A. Kock ◽  
D. L. Arévalo-Martínez ◽  
C. R. Löscher ◽  
H. W. Bange
Keyword(s):  
Linear Relationship ◽  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Open Ocean ◽  
Oxygen Utilization ◽  
Double Peak Structure ◽  
Peak Structure ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. Depth profiles of nitrous oxide (N2O) were measured during six cruises to the upwelling area and oxygen minimum zone (OMZ) off Peru in 2009 and 2012/13, covering both the coastal shelf region and the adjacent open ocean. N2O profiles displayed a strong sensitivity towards oxygen concentrations. Open ocean profiles showed a transition from a broad maximum to a double-peak structure towards the centre of the OMZ where the oxygen minimum was more pronounced. Maximum N2O concentrations in the open ocean were about 80 nM. A linear relationship between ΔN2O and apparent oxygen utilization (AOU) could be found for all measurements within the upper oxycline, with a slope similar to studies in other oceanic regions. N2O profiles close to the shelf revealed a much higher variability, with N2O concentrations in the upper oxycline reaching up to several hundred nanomoles per liter at selected stations. Due to the extremely sharp oxygen gradients at the shelf, these maxima occurred in very shallow water depths of less than 50 m. In this area, a linear relationship between ΔN2O and AOU could not be observed. N2O concentrations above 100 nM were observed at oxygen concentrations ranging from close to saturation to suboxic conditions. Our results indicate that the coastal upwelling off Peru at the shelf causes conditions that lead to extreme N2O accumulation.

Mid-Holocene extinction of cold-water corals on the Namibian shelf steered by the Benguela oxygen minimum zone

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1185-1188 ◽  
Author(s):  
Leonardo Tamborrino ◽  
Claudia Wienberg ◽  
Jürgen Titschack ◽  
Paul Wintersteller ◽  
Furu Mienis ◽  
...  
Keyword(s):  
Cold Water ◽  
Oxygen Minimum Zone ◽  
Uranium Series ◽  
Uranium Series Dating ◽  
Benguela Upwelling ◽  
Minimum Zone ◽  
Water Depths ◽  
Oxygen Minimum ◽  
Water Coral ◽  
Southeastern Atlantic

Abstract An exceptionally large cold-water coral mound province (CMP) was recently discovered extending over 80 km along the Namibian shelf (offshore southwestern Africa) in water depths of 160–270 m. This hitherto unknown CMP comprises >2000 mounds with heights of up to 20 m and constitutes the largest CMP known from the southeastern Atlantic Ocean. Uranium-series dating revealed a short but intense pulse in mound formation during the early to mid-Holocene. Coral proliferation during this period was potentially supported by slightly enhanced dissolved oxygen concentrations compared to the present Benguela oxygen minimum zone (OMZ). The subsequent mid-Holocene strengthening of the Benguela Upwelling System and a simultaneous northward migration of the Angola-Benguela Front resulted in an intensification of the OMZ that caused the sudden local extinction of the Namibian corals and prevented their reoccurrence until today.

Contribution of oxygen minimum zone waters to the coastal upwelling off Mauritania

2009 ◽  
Vol 83 (1-4) ◽  
pp. 143-150 ◽  
Author(s):  
Mirjam S. Glessmer ◽  
Carsten Eden ◽  
Andreas Oschlies
Keyword(s):  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals I/Ca ratios in benthic foraminifera from the Peruvian oxygen minimum zone: analytical methodology and evaluation as proxy for redox conditions

2014 ◽  
Vol 11 (7) ◽  
pp. 11635-11670 ◽  
Author(s):  
N. Glock ◽  
V. Liebetrau ◽  
A. Eisenhauer
Keyword(s):  
Benthic Foraminifera ◽  
Oxygen Minimum Zone ◽  
Individual Variability ◽  
Redox Conditions ◽  
Positive Trend ◽  
Analytical Methodology ◽  
Foraminiferal Species ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. In this study we explore the correlation of I/Ca ratios in three calcitic and one aragonitic foraminiferal species. I/Ca ratios are evaluated as possible proxies for changes in ambient redox conditions across the Peruvian oxygen minimum zone to the ambient oxygen concentrations in the habitat of the foraminiferal species studied. We test cleaning and measurement methods to determine I/Ca ratios in benthic foraminifera from the Peruvian oxygen minimum zone. All species show a positive trend in their I/Ca ratios as a function of higher oxygen concentrations and these trends are all statistically significant except for the aragonitic species Hoeglundina elegans. The most promising species appears to be Uvigerina striata which shows a highly statistically significant correlation between I/Ca ratios and bottom water (BW) oxygenation (I/Ca = 0.032(± 0.004)[O2]BW + 0.29(± 0.03), R2 = 0.61, F = 75, P < 0.0001). Although I/Ca ratios in benthic foraminifera might prove to be a valuable proxy for changing redox-conditions the iodine volatility in acidic solutions, the species dependency ofI/Ca–[O2]BW correlations, and the individual variability of single tests severely interfere with the observed I/Ca–[O2]BW relationship.

Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India

2016 ◽  
Vol 566-567 ◽  
pp. 1052-1061 ◽  
Author(s):  
Parthasarathi Chakraborty ◽  
Sucharita Chakraborty ◽  
Saranya Jayachandran ◽  
Ritu Madan ◽  
Arindam Sarkar ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Continental Margin ◽  
Bottom Water ◽  
Oxygen Minimum Zone ◽  
Minimum Zone ◽  
Oxygen Minimum
Sign in / Sign up

Export Citation Format

Share Document