Benthic foraminifera and climate change at the Paleocene/Eocene boundary. New approach. - In the ... more Benthic foraminifera and climate change at the Paleocene/Eocene boundary. New approach. - In the past as in present, climate changes are considered as major factors inducing physico-chemical parameters fluctuations of marine environment : acidity, oxygenation, nutrient intake. The disturbance of these parameters affects the benthic foraminiferal biodiversity in view of their extreme sensitivity. In this context, what are signatures of the global warming IETM (Initial Eocene Thermal Maximum) which marks the Paleocene/ Eocene boundary on the behaviour of benthic foraminifera at Kharrouba (Tunisia) and Zumaya (Spain) sections ? Quantitative analysis of all combined benthic foraminifera species in each section (Kharrouba and Zumaya) shows a brutal drop of specific richness, a signal of global warming impact. This upsetting is observed, not only on specific richness, but also on taxa distribution within sediments : Endobenthic Calcareous (EnC) and Endobenthic Agglutinated (EnA) ; and at their surfaces : Epibenthic Agglutinated (EpA) and Epibenthic Calcareous (EpC). Considered separately, the analysis of these four assemblages is a new approach allowing to better understanding the behaviour of benthic foraminiferal during the global warming (IETM) of the Paleocene-Eocene transition. Despite the Epibenthic percentage change is done in opposite way for Kharrouba and Zumaya sections, the percentages of Epibenthic Calcareous (EpC) and Epibenthic Agglutinated (EpA), considered separately, show a different reality. These two groups vary in same way at both sections. In contrast, the endobenthic behaviour is more complex. The variation of Endobenthic Calcareous (EnC) is done in the same direction in the two sections, showing a decrease in their frequency. But, for Endobenthic Agglutinated (EnA), the frequency varies in opposite way. For the Zumaya section they were up 36.65%, while in the Kharrouba section shows a slight decrease of 3.22%. The new reorganization of these four groups at lower Eocene is explained either by massive extinctions mainly for calcareous species and dissolution of their tests ; either by a passive dispersal of agglutinated species which are spared of the test dissolution. The precariousness of calcarous tests (into the sediments as at their surface) gives them quality as a best indicator of ocean acidification for the North Atlantic (Zumaya) and the Tethyan Ocean (Kharrouba). The increase of acidity is probably due to limitation of thermohaline circulation during global warming (IETM) in northern of Atlantic Ocean causing a much stronger corrosion to calcareous tests.
A new section at Jebel Gorraa, in northern Tunisia, contains the Paleocene–Eocene transition inte... more A new section at Jebel Gorraa, in northern Tunisia, contains the Paleocene–Eocene transition interval. Sample analysis of the section delivers abundant and diverse microfauna of planktonic and benthic foraminifera. Biostratigraphically, the Acarinina sibaiyaensis index-species is identified for the first time in this region, which allows us to specify the location of the Paleocene–Eocene boundary as well as the first E1 biozone of the lower Eocene. Samples from this biozone contain calcitic tests poorly preserved with an enrichment of iron oxide signifying a period of upheaval in local marine environments linked to the global warming of the Paleocene–Eocene Thermal Maximum (PETM), the marker for the P/E boundary.
At Kharrouba (near Tunis City in northern Tunisia), on the southern margin of the Tethyan realm, ... more At Kharrouba (near Tunis City in northern Tunisia), on the southern margin of the Tethyan realm, the Paleocene-Eocene (P-E) transition interval deposition is continuous and complete. Based on high-resolution analysis and quantitative data of planktonic and benthic foraminifera at the Kharrouba section, this transition interval records expanded deposition of the relevant standard planktonic foraminiferal biozones with indicative index species i.e.: Morozovella velascoensis for the latest Paleocene P5 zone, and Acarinina sibaiyaensis for the earliest Eocene E1 zone, Pseudohastigerina wilcoxensis for the E2 zone, Morozovella marginodentata for the E3 zone and Morozovella formosa for the E4 zone. This complete section contains benthic foraminiferal assemblages which include calcareous and agglutinated cosmopolitan deep-water species (DWBF). Among the calcareous deep benthic foraminifera Aragonia velascoensis Anomalinoides rubiginosus, Oridorsalis umbonatus, Nuttallides truempyi, Pullenia coryelli and Tappanina selmensis, are relatively abundant. These species are the main representatives of the Velasco fauna indicative of a bathyal-abyssal environment. Moreover, within this section, the agglutinated species e.g., Glomospira charoides, Karrerulina horrida, Rzehakina epigona, Ammodiscus spp. and Gaudryina pyramidata, assumed to be restricted to deep-sea palaeoenvironments, constitute an important proportion of the benthic foraminiferal assemblages. Therefore, during the Paleocene-Eocene transitional period, the Kharrouba area hosted many cosmopolitan deep-sea benthic foraminiferal species as was the case at Zumaya and several DSDP sites. The depth range tolerances of these deep-marine taxa, both with calcareous and agglutinated test, indicate that close to the P/E boundary, the Kharrouba area was located in the lower bathyal environment in the southern Tethys margin.
A high-resolution biostratigraphic and quantitative study with planktic foraminifera has allowed ... more A high-resolution biostratigraphic and quantitative study with planktic foraminifera has allowed to identify the most probable position of the Paleocene/Eocene (P/E) boundary at the Kharrouba section (northern Tunisia). The P/E boundary is placed in coincidence with the base of a dark clayey interval with calcareous test dissolution and domin ance of agglutinated benthic foraminifera, the sudden decrease of the benthic foraminiferal species richness, the base of an acme of planktic foraminiferal genus Acarinina and the first occurrence of Acarinina sibaiyaensis (base of the Biozone E1). These horizons are related in other sections to the decrease of the isotopic relation δ13C (base of CIE), which was chosen key-horizon of the P/E boundary. It corresponds to the most intensive hyperthermal event (PETM) and benthic foraminiferal extinction event (BFEE) of the Cenozoic.
Benthic foraminifera and climate change at the Paleocene/Eocene boundary. New approach. - In the ... more Benthic foraminifera and climate change at the Paleocene/Eocene boundary. New approach. - In the past as in present, climate changes are considered as major factors inducing physico-chemical parameters fluctuations of marine environment : acidity, oxygenation, nutrient intake. The disturbance of these parameters affects the benthic foraminiferal biodiversity in view of their extreme sensitivity. In this context, what are signatures of the global warming IETM (Initial Eocene Thermal Maximum) which marks the Paleocene/ Eocene boundary on the behaviour of benthic foraminifera at Kharrouba (Tunisia) and Zumaya (Spain) sections ? Quantitative analysis of all combined benthic foraminifera species in each section (Kharrouba and Zumaya) shows a brutal drop of specific richness, a signal of global warming impact. This upsetting is observed, not only on specific richness, but also on taxa distribution within sediments : Endobenthic Calcareous (EnC) and Endobenthic Agglutinated (EnA) ; and at their surfaces : Epibenthic Agglutinated (EpA) and Epibenthic Calcareous (EpC). Considered separately, the analysis of these four assemblages is a new approach allowing to better understanding the behaviour of benthic foraminiferal during the global warming (IETM) of the Paleocene-Eocene transition. Despite the Epibenthic percentage change is done in opposite way for Kharrouba and Zumaya sections, the percentages of Epibenthic Calcareous (EpC) and Epibenthic Agglutinated (EpA), considered separately, show a different reality. These two groups vary in same way at both sections. In contrast, the endobenthic behaviour is more complex. The variation of Endobenthic Calcareous (EnC) is done in the same direction in the two sections, showing a decrease in their frequency. But, for Endobenthic Agglutinated (EnA), the frequency varies in opposite way. For the Zumaya section they were up 36.65%, while in the Kharrouba section shows a slight decrease of 3.22%. The new reorganization of these four groups at lower Eocene is explained either by massive extinctions mainly for calcareous species and dissolution of their tests ; either by a passive dispersal of agglutinated species which are spared of the test dissolution. The precariousness of calcarous tests (into the sediments as at their surface) gives them quality as a best indicator of ocean acidification for the North Atlantic (Zumaya) and the Tethyan Ocean (Kharrouba). The increase of acidity is probably due to limitation of thermohaline circulation during global warming (IETM) in northern of Atlantic Ocean causing a much stronger corrosion to calcareous tests.
A new section at Jebel Gorraa, in northern Tunisia, contains the Paleocene–Eocene transition inte... more A new section at Jebel Gorraa, in northern Tunisia, contains the Paleocene–Eocene transition interval. Sample analysis of the section delivers abundant and diverse microfauna of planktonic and benthic foraminifera. Biostratigraphically, the Acarinina sibaiyaensis index-species is identified for the first time in this region, which allows us to specify the location of the Paleocene–Eocene boundary as well as the first E1 biozone of the lower Eocene. Samples from this biozone contain calcitic tests poorly preserved with an enrichment of iron oxide signifying a period of upheaval in local marine environments linked to the global warming of the Paleocene–Eocene Thermal Maximum (PETM), the marker for the P/E boundary.
At Kharrouba (near Tunis City in northern Tunisia), on the southern margin of the Tethyan realm, ... more At Kharrouba (near Tunis City in northern Tunisia), on the southern margin of the Tethyan realm, the Paleocene-Eocene (P-E) transition interval deposition is continuous and complete. Based on high-resolution analysis and quantitative data of planktonic and benthic foraminifera at the Kharrouba section, this transition interval records expanded deposition of the relevant standard planktonic foraminiferal biozones with indicative index species i.e.: Morozovella velascoensis for the latest Paleocene P5 zone, and Acarinina sibaiyaensis for the earliest Eocene E1 zone, Pseudohastigerina wilcoxensis for the E2 zone, Morozovella marginodentata for the E3 zone and Morozovella formosa for the E4 zone. This complete section contains benthic foraminiferal assemblages which include calcareous and agglutinated cosmopolitan deep-water species (DWBF). Among the calcareous deep benthic foraminifera Aragonia velascoensis Anomalinoides rubiginosus, Oridorsalis umbonatus, Nuttallides truempyi, Pullenia coryelli and Tappanina selmensis, are relatively abundant. These species are the main representatives of the Velasco fauna indicative of a bathyal-abyssal environment. Moreover, within this section, the agglutinated species e.g., Glomospira charoides, Karrerulina horrida, Rzehakina epigona, Ammodiscus spp. and Gaudryina pyramidata, assumed to be restricted to deep-sea palaeoenvironments, constitute an important proportion of the benthic foraminiferal assemblages. Therefore, during the Paleocene-Eocene transitional period, the Kharrouba area hosted many cosmopolitan deep-sea benthic foraminiferal species as was the case at Zumaya and several DSDP sites. The depth range tolerances of these deep-marine taxa, both with calcareous and agglutinated test, indicate that close to the P/E boundary, the Kharrouba area was located in the lower bathyal environment in the southern Tethys margin.
A high-resolution biostratigraphic and quantitative study with planktic foraminifera has allowed ... more A high-resolution biostratigraphic and quantitative study with planktic foraminifera has allowed to identify the most probable position of the Paleocene/Eocene (P/E) boundary at the Kharrouba section (northern Tunisia). The P/E boundary is placed in coincidence with the base of a dark clayey interval with calcareous test dissolution and domin ance of agglutinated benthic foraminifera, the sudden decrease of the benthic foraminiferal species richness, the base of an acme of planktic foraminiferal genus Acarinina and the first occurrence of Acarinina sibaiyaensis (base of the Biozone E1). These horizons are related in other sections to the decrease of the isotopic relation δ13C (base of CIE), which was chosen key-horizon of the P/E boundary. It corresponds to the most intensive hyperthermal event (PETM) and benthic foraminiferal extinction event (BFEE) of the Cenozoic.
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Foraminifera 2 by ZILI Lamia
changes are considered as major factors inducing physico-chemical parameters fluctuations of marine environment : acidity, oxygenation,
nutrient intake. The disturbance of these parameters affects the benthic foraminiferal biodiversity in view of their extreme sensitivity.
In this context, what are signatures of the global warming IETM (Initial Eocene Thermal Maximum) which marks the Paleocene/
Eocene boundary on the behaviour of benthic foraminifera at Kharrouba (Tunisia) and Zumaya (Spain) sections ?
Quantitative analysis of all combined benthic foraminifera species in each section (Kharrouba and Zumaya) shows a brutal drop of specific
richness, a signal of global warming impact. This upsetting is observed, not only on specific richness, but also on taxa distribution
within sediments : Endobenthic Calcareous (EnC) and Endobenthic Agglutinated (EnA) ; and at their surfaces : Epibenthic Agglutinated
(EpA) and Epibenthic Calcareous (EpC).
Considered separately, the analysis of these four assemblages is a new approach allowing to better understanding the behaviour of
benthic foraminiferal during the global warming (IETM) of the Paleocene-Eocene transition. Despite the Epibenthic percentage change
is done in opposite way for Kharrouba and Zumaya sections, the percentages of Epibenthic Calcareous (EpC) and Epibenthic Agglutinated
(EpA), considered separately, show a different reality. These two groups vary in same way at both sections.
In contrast, the endobenthic behaviour is more complex. The variation of Endobenthic Calcareous (EnC) is done in the same direction
in the two sections, showing a decrease in their frequency. But, for Endobenthic Agglutinated (EnA), the frequency varies in opposite
way. For the Zumaya section they were up 36.65%, while in the Kharrouba section shows a slight decrease of 3.22%.
The new reorganization of these four groups at lower Eocene is explained either by massive extinctions mainly for calcareous species
and dissolution of their tests ; either by a passive dispersal of agglutinated species which are spared of the test dissolution. The precariousness
of calcarous tests (into the sediments as at their surface) gives them quality as a best indicator of ocean acidification for the
North Atlantic (Zumaya) and the Tethyan Ocean (Kharrouba). The increase of acidity is probably due to limitation of thermohaline
circulation during global warming (IETM) in northern of Atlantic Ocean causing a much stronger corrosion to calcareous tests.
changes are considered as major factors inducing physico-chemical parameters fluctuations of marine environment : acidity, oxygenation,
nutrient intake. The disturbance of these parameters affects the benthic foraminiferal biodiversity in view of their extreme sensitivity.
In this context, what are signatures of the global warming IETM (Initial Eocene Thermal Maximum) which marks the Paleocene/
Eocene boundary on the behaviour of benthic foraminifera at Kharrouba (Tunisia) and Zumaya (Spain) sections ?
Quantitative analysis of all combined benthic foraminifera species in each section (Kharrouba and Zumaya) shows a brutal drop of specific
richness, a signal of global warming impact. This upsetting is observed, not only on specific richness, but also on taxa distribution
within sediments : Endobenthic Calcareous (EnC) and Endobenthic Agglutinated (EnA) ; and at their surfaces : Epibenthic Agglutinated
(EpA) and Epibenthic Calcareous (EpC).
Considered separately, the analysis of these four assemblages is a new approach allowing to better understanding the behaviour of
benthic foraminiferal during the global warming (IETM) of the Paleocene-Eocene transition. Despite the Epibenthic percentage change
is done in opposite way for Kharrouba and Zumaya sections, the percentages of Epibenthic Calcareous (EpC) and Epibenthic Agglutinated
(EpA), considered separately, show a different reality. These two groups vary in same way at both sections.
In contrast, the endobenthic behaviour is more complex. The variation of Endobenthic Calcareous (EnC) is done in the same direction
in the two sections, showing a decrease in their frequency. But, for Endobenthic Agglutinated (EnA), the frequency varies in opposite
way. For the Zumaya section they were up 36.65%, while in the Kharrouba section shows a slight decrease of 3.22%.
The new reorganization of these four groups at lower Eocene is explained either by massive extinctions mainly for calcareous species
and dissolution of their tests ; either by a passive dispersal of agglutinated species which are spared of the test dissolution. The precariousness
of calcarous tests (into the sediments as at their surface) gives them quality as a best indicator of ocean acidification for the
North Atlantic (Zumaya) and the Tethyan Ocean (Kharrouba). The increase of acidity is probably due to limitation of thermohaline
circulation during global warming (IETM) in northern of Atlantic Ocean causing a much stronger corrosion to calcareous tests.