A concentration of exceptionally well-preserved large tubular foraminifera in the Eocene Zumaya flysch, northern Spain

T. P. Crimes; A. Uchman

doi:10.1017/s0016756800023219

A concentration of exceptionally well-preserved large tubular foraminifera in the Eocene Zumaya flysch, northern Spain

Geological Magazine ◽

10.1017/s0016756800023219 ◽

1993 ◽

Vol 130 (6) ◽

pp. 851-853 ◽

Cited By ~ 4

Author(s):

T. P. Crimes ◽

A. Uchman

Keyword(s):

Ocean Floor ◽

Bottom Current ◽

Northern Spain

AbstractA concentration of exceptionally well-preserved large tubular foraminifera occurs on a specimen from the sole of a sandstone bed from the Eocene Zumaya flysch. The foraminifera were probably washed out from the sediment by a weak bottom current, orientated and concentrated in a pre-existing depression on the ocean floor. Fortunately, subsequently deposited turbidite sand, which forms the host bed, only disturbed the fossils to an infinitesimal degree.

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PREDICTING BOTTOM CURRENT DEPOSITION AND EROSION ON THE OCEAN FLOOR

10.31223/x58g8r ◽

2021 ◽

Author(s):

Daan Beelen ◽

Lesli Wood

Keyword(s):

Ocean Floor ◽

Resource Extraction ◽

Bottom Current ◽

Model Data ◽

Data Types ◽

Erosion And Deposition ◽

Generalized Patterns ◽

Oceanographic Data ◽

High Resolution Bathymetry ◽

Current Systems

Three types of oceanographic data are integrated in this study to predict thermohaline geostrophic bottom current deposition and erosion on the ocean floor. These data types are, 1) high-resolution bathymetry, 2) numerical model data of bottom current shear stress and 3) model data of the distribution and amount of sediment on the ocean floor. Intervals of thermohaline geostrophic bottom current deposition and erosion can be quantified from this information, which are then be extrapolated across the ocean floor in 4.5 x 9.3 km grid-size resolution. The results of this analysis are displayed on a map that shows the distribution of zones of bottom current erosion and deposition. This map is then cross-referenced for accuracy using documented examples of mapped erosional and depositional bottom current systems, which demonstrates this study’s approach has strong predictive capabilities. The model developed herein is used to derive boundaries for depositional bottom current regimes and formulate generalized patterns that contribute to bottom current erosion and deposition, and then discuss the importance of these interpretations for resource extraction and ocean floor mapping.

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Measurements of a Small Near-Bottom Cyclonic Circulation Near the Gulf Stream Axis

Journal of the Fisheries Research Board of Canada ◽

10.1139/f76-268 ◽

1976 ◽

Vol 33 (10) ◽

pp. 2197-2202 ◽

Cited By ~ 1

Author(s):

R. A. Clarke

Keyword(s):

Gulf Stream ◽

Cyclonic Circulation ◽

Triangular Array ◽

Ocean Floor ◽

Bottom Current

Data from near-bottom current meters moored in a small triangular array (25 km/side) plus hydrographic sections reveal the presence of a near-bottom cyclonic circulation with a radius of 50 km and velocity of 10 cm/s just north of the Gulf Stream near 50°W. The circulation extends to at least 1350 m from the ocean floor and was observed over a period of 9 days during which time it moved southward toward the Stream with speeds of 0.5–15 cm/s. The strength of the circulation decreases somewhat with distance from the bottom.

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Ferruginous bioforms accumulations in deep marine environments: an approach to their origin and formation mechanisms in the Transitional Zone province of the Galician Continental Margin (NW Iberian Peninsula)

10.5194/egusphere-egu2020-4165 ◽

2020 ◽

Author(s):

Ángel Enrique López-Pérez ◽

Belén Rubio ◽

Daniel Rey ◽

Luís Pinheiro

Keyword(s):

Steady State ◽

Continental Margin ◽

Deep Ocean ◽

Direct Consequence ◽

Transitional Zone ◽

Ocean Floor ◽

Bottom Current ◽

Formation Mechanisms ◽

Bottom Currents ◽

Sea Bottom

Ferruginous tubular structures concretions are widely distributed over the seafloor surrounding the Gran Burato depression in the Transitional Zone (TZ) province of the Galician Continental Margin (NW Iberian Margin). These bioforms-like structures are created by iron oxides precipitations into the tube-dwelling macrozoobenthos as a result of Fe2+ upward diffusion and O2 ventilation and diffusion acting in the water-sediment interphase in a non-steady state early diagenesis. X-ray diffraction analyses display that goethite is the main mineralogical component of these bioforms-like structures. Furthermore, non-steady state diagenesis has been identified by several oxidations fronts recognised in three piston cores, reflecting that the redoxcline has not achieved the deeper equilibrium in the study area. Afterwards, these ferruginous tubes were eroded, remobilised and redistributed over the seabed by bottom currents. Ocean-floor observations show erosion and sea-bottom current structures as ripples, grooves, erratic blocks, accumulations of pteropods and carbonate crusts associated with hardgrounds. Sedimentation rates calculated in a piston core display very low values for the last 30 cal ka BP (mean of 1.57 cm ky&#8722;1) with a marked hiatus between 17.80 to 10.45 cal ka BP, meanwhile abraded surfaces have been identified by high-resolution seismic data confirming erosional processes in this area of the TZ province. We conclude that the ferruginous bioforms accumulation over the deep-ocean floor is indicative of a present-day vigorous seafloor current acting and eroding the sediments of the TZ province. This bottom current is a direct consequence of the general seafloor elevation of the TZ province that causes constriction of the water masses (MOW and LSW) that induces a general intensification of the bottom currents and greater erosional capacity. This erosional process causes the continuous oxygenation of the upper sediments, and it prevents to reach the steady-state diagenesis, playing this fact an essential role in the ferruginous formations and accumulations in the study area.

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