Surface- and deep-water response to the Early Aptian OAE 1a in the western Tethys

2021 ◽  
Author(s):  
Cinzia Bottini ◽  
Victor M. Giraldo-Gómez ◽  
Maria Rose Petrizzo ◽  
Elisabetta Erba
Keyword(s):  
Deep Water ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Black Shales ◽  
Ontong Java Plateau ◽  
Western Tethys ◽  
Organic Carbon Flux ◽  
Water Response ◽  
Matter Flux

<p>The Cretaceous was punctuated by interludes of widespread deposition of organic-rich sediments (black shales) in the oceans and epicontinental seas, named Oceanic Anoxic Events (OAE)s, representing major alterations in the global carbon budget. The early Aptian OAE 1a (ca. 120 Ma) coincided with a global paleoclimatic and paleoenvironmental perturbation which lasted for ca. 1.1 Myrs probably triggered by volcanogenic CO<sub>2 </sub>emissions associated with the emplacement of the Ontong Java Plateau. To date, there is a comprehensive characterization of OAE 1a paleoceanographic conditions and paleoecology of surface-waters while less information is available for bottom-water evolution. In this regard, benthic foraminifera are ideal to characterize deep-water oxygen levels and the organic carbon flux. We present a high-resolution study of benthic foraminiferal assemblages across OAE 1a in the Cismon Core (western Tethys, Lombardy Basin, Northern Italy). Contrarily to many sites, the Cismon Core yields benthic foraminifera also in the Selli Level thus providing information about deep-water conditions during OAE 1a. Our data are indicative of fluctuations in bottom-water oxygenation and organic-matter flux to the sea-floor prior to, during and after OAE 1a. The integration of the new benthic foraminiferal data with calcareous nannofossil and planktonic foraminiferal datasets is here used to produce a model of surface- to bottom-water paleowater evolution through the latest Barremian-early late Aptian. In particular, the new data show coeval changes in bottom- and surface-waters conditions prior to and at the onset of OAE 1a. Anoxia was reached during the core of the negative carbon isotope anomaly, under maximum warming and higher surface-water fertility. Conversely, the repopulation of benthic foraminifera postponed the plankton recovery. Benthic foraminifera data at Cismon show, for the first time, evidence of a repopulation event during the OAE 1a suggestive for a slight increase in the supply of oxygen to the seafloor during the Selli Level deposition.</p>

scholarly journals The Registration of the Mid-Paleocene Biotic Event (MPBE) in Tunisia

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Narjess Karoui-Yaakoub ◽  
Moncef Saïd Mtimet ◽  
Mohamed Hédi Negra ◽  
Chaima Grira ◽  
Wafa Gusemi
Keyword(s):  
Iron Oxides ◽  
Deep Water ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Rare Species ◽  
Planktonic Foraminifera ◽  
Dissolution Process ◽  
Dissolution Tests ◽  
First Time ◽  
El Haria Formation

In Tunisia, the Paleocene biomarkers are identified within the El Haria Formation shales. The Selandian is absent in most of the Paleocene outcrops and the Thanetian is unconformable to different stages of the Cretaceous. In the middle of Selandian, with the beginning of the Globanomalina pseudomenardii (P4) zone, we note that the assemblage of planktonic foraminifera becomes very poorly preserved and much less abundant than at the base. It is represented by rare species and there has been a start of the microfauna dissolution tests and an enrichment in iron oxides, silica, and gypsum crystals. The dissolution process is increasing more and more and a drop in the content of carbonates is clearly recorded at the top of Selandian. However, we note that some small benthic foraminifera belonging to the genera Lenticulina and Anomalina escape the dissolution and very few planktonic foraminifera belonging to the genera Subbotina are preserved. This dramatic and abnormal dissolution extends over a considerable thickness. These features could be an expression of the mid-Paleocene biotic event (MPBE), registered for the first time in Tunisia. This intense dissolution is caused probably by the change in the solubility of carbonates, which may be related to the changes in the deep-water circulation or to the change in the productivity of the surface waters.

Oceanic Anoxic Event 1d (late Albian) in deep-water sediments of the Outer Carpathians, Poland; Carbon isotope and agglutinated foraminiferal records

2021 ◽  
Author(s):  
Krzysztof Bąk ◽  
Górny Zbigniew ◽  
Marta Bąk
Keyword(s):  
Carbon Isotope ◽  
Deep Water ◽  
Environmental Parameters ◽  
Taxonomic Composition ◽  
Black Shales ◽  
Feeding Strategies ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Lithostratigraphic Units ◽  
Outer Carpathians

<p>The Albian–Cenomanian transition is stratigraphically still poorly constrained in deep-water environments below the CCD. For this reason, the recognition of the OAE1d in such sedimentary records is extremely rare. Our high-resolution carbon-isotope (δ<sup>13</sup>C<sub>org</sub>) stratigraphy of the Upper Albian and Lower Cenomanian turbidite/hemipelagic succession, accumulated in the marginal Silesian Basin of the Western Tethys, made it possible to identify the interval corresponding to the OAE1d. It has been recognized within two lithostratigraphic units of the Silesian Nappe of the Outer Carpathians (the Lower and Middle Lgota Beds), which are composed mostly of turbidite sediments containing a large amount of bioclastic material occurring in the silty and sandy fraction (locally over 70%). Bioclasts were redeposited from marginal shelf of the European Platform. The hemipelagic non-calcareous claystones which separate the turbidite sequences contain deep-water agglutinated foraminiferal (DWAF) assemblages, and are devoid of calcareous benthic foraminifers.</p><p>Using the analysis of the DWAF morphogroups, as well as changes in the benthos abundance and its taxonomic composition in relation to the characteristics (colour and TOC content) of hemipelagic sediments, we indicated changes in the environmental conditions that took place during the OAE1d at the bottom of the Silesian Basin. The most abundant horizons of organic-rich shales are characteristic of the lower part of the OAE1d succession corresponding to the Pialli Level from the Umbria-Marche Basin, although thin intercalations of black shales are also present along the upper part of this succession, where the hemipelagic sediments are dominated by green-coloured shales. The variability of organic matter in the studied sediments only slightly correlates with the abundance of the DWAFs and with their taxonomic composition. The more visible features in the latest Albian agglutinated benthos concern relative proportions of foraminiferal morphogroups which correspond to life-style and feeding strategies, and in this way reflect changes in selected environmental parameters. It seems that fluctuations in the morphogroup distribution along the OAE1d succession reflects the influence of two groups of factors: (i) oxygen concentration in bottom waters (low in the older part of the OAE1d, with fluctuations in the younger part of this isotope event), and (ii) the organic carbon flux that was linked to the onset of a massive redeposition of biogenic material from the European shelf. The last factor is related to the sea level fall during the 3-rd order regressive cycle.</p>

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.

scholarly journals Termination of Organic-Rich Accumulation of the Oceanic Anoxic Event 2 in the Deep-Water Carpathian Basins Based on Carbon Stable Isotope Data

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 420
Author(s):  
Marta Bąk ◽  
Krzysztof Bąk
Keyword(s):  
Stable Isotope ◽  
Deep Water ◽  
Black Shales ◽  
Carbon Stable Isotope ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Isotope Data ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Stable Isotope Data

Organic-rich black shales intercalated with green radiolarian shales and bentonites, 2.2 m thick, represent an equivalent of the Bonarelli Level in the Outer Carpathian deep-water succession. Carbon stable isotope data from four sections in the Outer Carpathians show that termination of organic-rich accumulation, related to the oceanic anoxic event 2 (OAE2), occurred at the same time in this part of the Western Tethys. The excellent marker of this event is a first horizon of Fe–Mn layer (nodules), a few centimeters thick, directly covering the youngest black shale layer of the Bonarelli-equivalent Level, which is regarded as the regional chronohorizon. The youngest succession of the organic-rich shales, ca. 30 cm thick, corresponds to the latest Cenomanian interval of δ13Corg values displaying a negative trend, which represents a terminal part within the OAE2 carbon isotope excursion. A deep negative shift which ends this falling trend, close to the Cenomanian–Turonian boundary in δ13C curves from many sections around the world, is not visible in the Outer Carpathian successions. The reason for this was the long period of stratigraphic condensation, which is reflected in the ferromanganese sediments of this area.

scholarly journals Landscape Mapping, Ichnological and Benthic Foraminifera Trends in a Deep-Water Gateway, Discovery Gap, NE Atlantic

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 474
Author(s):  
Evgenia V. Dorokhova ◽  
Francisco J. Rodríguez-Tovar ◽  
Dmitry V. Dorokhov ◽  
Liubov A. Kuleshova ◽  
Anxo Mena ◽  
...  
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Sediment Cores ◽  
Abiotic Factor ◽  
Bottom Water Temperature ◽  
Temporal Differences ◽  
Landscape Mapping ◽  
Position Index ◽  
Macro Benthos

Multidisciplinary studies have allowed us to describe the abiotic landscapes and, thus, reveal the ichnological and benthic foraminifera trends in a deep-water gateway. Mesoscale landscape mapping is presented based on the bathymetric position index, substrate types and near-bottom water temperature. Four sediment cores, retrieved from the entrance, centre and exit of the gap, were subject to computed tomography, ichnological and benthic foraminifera studies. A high diversity of abiotic landscapes in the relatively small area of Discovery Gap is detected and its landscape is characterized by 23 landscape types. The most heterogeneous abiotic factor is a topography that is associated with sediment patchiness and substrate variability. The ichnological and tomographical studies of the sediment cores demonstrate lateral and temporal differences in the macrobenthic tracemaker behaviour. The ichnofossils assemblage of the sediment core can be assigned to the Zoophycos ichnofacies with a higher presence of Zoophycos in the entrance site of the gap and during glacial intervals. Higher benthic foraminifera diversity and species richness during the Holocene are also registered in the southern part of the gap compared to the northern part. The spatial and temporal differences in macro-benthos behavior and benthic foraminifera distribution in the deep-water gateway are proposed to relate to the topographical variations of the Antarctic Bottom Water and its influence on the hydrodynamic regime, nutrient transport, etc.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths &gt;1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths &lt;300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths &lt;300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

scholarly journals 14C in the Deep Water of the East Atlantic

Radiocarbon ◽  
1986 ◽  
Vol 28 (2A) ◽  
pp. 391-396 ◽  
Author(s):  
Reiner Schlitzer
Keyword(s):  
Deep Water ◽  
Large Scale ◽  
Bottom Water ◽  
Source Parameters ◽  
Potential Temperature ◽  
Source Terms ◽  
East Atlantic ◽  
The West ◽  
Model Calculations ◽  
Inflowing Water

The renewal of east Atlantic deep water and its large-scale circulation and mixing have been studied in observed distributions of temperature, silicate, ΣCO2, and 14C. 14C variations in northeast Atlantic deep water below 3500m depth are small. Δ14C values range from − 100‰ to −125‰. 14C bottom water concentrations decrease from Δ14C =−117‰ in the Sierra Leone Basin to Δ14C = − 123‰ in the Iberian Basin and are consistent with a mean northward bottom water flow. The characteristic of the water that flows from the west Atlantic through the Romanche Trench into the east Atlantic was determined by inspection of θ/Δ14C and θ/SiO2 diagrams. A mean potential temperature of θ = 1.50 ± .05°C was found for the inflowing water. A multi-box model including circulation, mixing, and chemical source terms in the deep water has been formulated. Linear programing and least-squares techniques have been used to obtain the transport and source parameters of the model from the observed tracer fields. Model calculations reveal an inflow through the Romanche Trench from the west Atlantic, which predominates over any other inflow, of (5 ± 2) Sv (potential temperature 1.50°C), a convective turnover of (150 ± 50) years and a vertical apparent diffusivity of (4 ± 1) cm2/s. Chemical source terms are in the expected ranges.

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