High-resolution stratigraphy and turbidite processes in the Seine Abyssal Plain, northwest Africa

1997 ◽  
Vol 17 (2) ◽  
pp. 147-153 ◽  
Author(s):  
T. L. Davies ◽  
B. Van Niel ◽  
Robert B. Kidd ◽  
P. P. E. Weaver
2020 ◽  
Author(s):  
D. Tiwari ◽  
W. Gao ◽  
A. Nangarla ◽  
P. Bhowmik ◽  
B. Sayers

2019 ◽  
Author(s):  
Wilken-Jon von Appen ◽  
Volker H. Strass ◽  
Astrid Bracher ◽  
Hongyan Xi ◽  
Cora Hörstmann ◽  
...  

2019 ◽  
Author(s):  
Wilken-Jon von Appen ◽  
Volker H. Strass ◽  
Astrid Bracher ◽  
Hongyan Xi ◽  
Cora Hörstmann ◽  
...  

Abstract. Nutrient rich water upwells offshore of Northwest Africa and is subsequently advected westwards. There it forms eddies and filaments with a rich spatial structure of physical and biological/biogeochemical properties. Here we present a high resolution (2.5 km) section through upwelling filaments and an eddy obtained in May 2018 with a Triaxus towed vehicle equipped with various oceanographic sensors. Physical processes at the mesoscale and submesoscale such as symmetric instability, trapping of fluid in eddies, and subduction of low potential vorticity (which we use as a water mass tracer) water can explain the observed distribution of biological production and export. We found a nitrate excess (higher nitrate concentrations than would be expected from oxygen values if only influenced by production and remineralization processes) core of an anti-cyclonic mode water eddy. We also found a high nitrate concentration region of ~5 km width in the mixed layer where symmetric instability appears to have injected nutrients from below into the euphotic zone. A similar region a little further south had high chlorophyll-a concentrations suggesting that nutrients had been injected there a few days earlier. Considering that such interactions of physics and biology are ubiquitous in the world's upwelling regions, we assume that they have strong influences on the productivity of such systems and their role in CO2 uptake. The intricate interplay of different parameters at kilometer scale needs to be taken into account when interpreting single profile and/or bottle data in dynamically active regions of the ocean.


2018 ◽  
Vol 34 (2) ◽  
pp. 737
Author(s):  
Ο. ΤΣΑΛΚΙΤΖΗ ◽  
Γ. ΑΝΑΣΤΑΣΑΚΗΣ

A detailed sedimentological study has been performed on five long piston cores recovered from the Balearic Abyssal Plain, the largest plain in the Mediterranean Sea. All the cores were dominated by multiple turbidite sequences, most of them displaying pronounced upward fining. The presence of a megaturbidite bed representing a single depositional event is observed in all the cores. Biostratigraphic correlation of the interlayered pelagic beds, using a high resolution nannofossil zonal scheme, suggests that the sediments in the cores date back to 50-100kyrs BP and that the age of the megabed is less than 50kyrs BP. The sedimentation rates for the last 50kyrs (over 50cm/Kyr) are greater in the northern and central Balearic Plain as compared to the lower sedimentation rates of 40cm/Kyr in the southern margin of the plain. Sedimentation rates (9,7-13,4cm/Kyr) are significantly reduced in the time interval between 50-120kyrs. The emplacement of the megaturbidite and the minor turbidites coincide with the sea level low stands. During these periods, great part of the continental shelf was revealed and processes sush as erosion, transportation and position became more intense.


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