Selectivity of foraminiferal extinction in the late Eocene

Paleobiology ◽  
1997 ◽  
Vol 23 (3) ◽  
pp. 347-357 ◽  
Author(s):  
Amit Banerjee ◽  
George E. Boyajian
Keyword(s):  
Benthic Foraminifera ◽  
Middle Eocene ◽  
Late Eocene ◽  
Mass Extinctions ◽  
Larger Benthic Foraminifera ◽  
Late Paleocene ◽  
Risk Of Extinction ◽  
Extinction Event

Late Eocene foraminiferal extinction shows diverse patterns of selective morphologic and latitudinal extinction. Taxa with discoidal shape, calcareous tests, and narrow and low-latitudinal ranges are at significantly greater risk of extinction. Elevated extinction intensities in calcareous tests are mainly due to the presence of larger benthic foraminifera that evolved in late Paleocene and diversified through the lower to middle Eocene. Selectivity of late Eocene foraminiferal extinction indicates that this extinction event was not a globally uniform event. Although this result does not verify an extraterrestrial impact or any other proposed cause of extinction, it does constrain the causes of late Eocene extinction. Furthermore, the geography of late Eocene foraminiferal extinction, and previously studied Cenomanian/Turonian extinction, demonstrates that mass extinctions exhibit different patterns of selectivity.

The incidence of unusual test morphologies of Eocene Larger benthic foraminifera: An example of Paleogene Adriatic Carbonate Platform

2021 ◽  
Author(s):  
Vlasta Ćosović ◽  
Jelena Španiček ◽  
Katica Drobne ◽  
Ervin Mrinjek
Keyword(s):  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Middle Eocene ◽  
Morphological Diversity ◽  
Late Eocene ◽  
Early Eocene ◽  
Coralline Red Algae ◽  
Larger Benthic Foraminifera ◽  
Shallow Marine ◽  
Scientific Project

<p>The Paleogene Adriatic carbonate platform(s) existed within the Central NeoTethys (around 32 N paleolatitude) from the Danian to the late Eocene (Bartonian/Priabonian) and produced a succession of limestones up to 500 m thick, rich in larger benthic foraminifera (LBF). The Eocene sediments are widely distributed along the eastern Adriatic coast and have been studied for many years. Taking into account the climatic changes that took place within the Eocene (Early Eocene and Middle Eocene climatic optima, known as EECO, MECO), special attention was paid to the composition of shallow-marine foraminiferal assemblages. The studies reveal the following trends: (1) the alveolinid-dominated assemblages were replaced by nummulitid-dominated assemblages around the MECO; (2) the greater species and morphological diversity (spherical, ellipsoid, extremely elongated fusiform) of the alveolinid fauna was evident at the EECO; (3) the nummulitid-dominated fauna was characterized by less diversified assemblages compared to the alveolinid ones and by the co-occurrence of scleractinian corals, coralline red algae and aborescent foraminifera. The occurrence of twin embryos has been assigned to the early Eocene in the alveolinid populations, especially in Alveolina levantina and A. axiampla (in some sections, the frequency is greater than 5%), and these coalesced embryos have the same size as the single form (usually they are smaller). The LBF assemblages of Middle Eocene showed a greater frequency of doubled adult tests (Orbitolites sp., Nummulites sp.). The origin of these unusual morphologies is poorly known, usually described as the results of stressful conditions. Considering the timing of the appearance of such morphologies, temperature and associated changes in the shallow-marine environment could be the cause.</p><p>This study is carried out as part of the scientific project IP-2019-04-5775 BREEMECO, funded by Croatian Scientific Foundation.</p>

Larger Benthic Foraminifera from the Panna and Mukta Fields Offshore India: Paleobiogeographical Implications

2019 ◽  
Vol 49 (3) ◽  
pp. 243-258
Author(s):  
Laura J. Cotton ◽  
V. Paul Wright ◽  
Andrew Barnett ◽  
Willem Renema
Keyword(s):  
Shallow Water ◽  
Benthic Foraminifera ◽  
Late Eocene ◽  
Marine Biodiversity ◽  
Upper Eocene ◽  
Larger Benthic Foraminifera ◽  
Geographic Ranges ◽  
Extinction Event ◽  
Global Events ◽  
Insight Into

Abstract A previously undocumented, diverse assemblage of very shallow-water larger benthic foraminifera (LBF) is described from the Panna-Mukta fields, offshore India. This location lies at the margin of the late Eocene to early Miocene Arabian Peninsula marine biodiversity hotspot. The assemblage has similar characteristics to those from the Middle East, Oman and Turkey, but shares little in common with onshore western Indian assemblages. In addition, the material contains several unusual and possibly new taxa, and extends the geographic ranges of several existing LBF. The succession spans the Eocene and Oligocene, with an unconformity between the middle and upper Eocene. As such it offers insight into the response of shallow-water taxa to the Eocene–Oligocene Transition extinction event from an unusual setting in a little studied region. Our data show that LBF taxonomic richness in the Panna Mukta fields is comparable with highly diverse assemblages found in Oman, indicating it may be an eastward extension of this high diversity region. Moreover, significant decreases in diversity are seen between the middle and upper Eocene and the upper Eocene and Oligocene. Major extinctions are known to occur in global LBF records at both of these levels, and the Panna Mukta succession therefore further confirms these are global events, extending across the platform and having a dramatic (at least short-term) effect on high biodiversity regions.

Crocodilian diversity in space and time: the role of climate in paleoecology and its implication for understanding K/T extinctions

Paleobiology ◽  
1998 ◽  
Vol 24 (4) ◽  
pp. 470-497 ◽  
Author(s):  
Paul J. Markwick
Keyword(s):  
Northern Hemisphere ◽  
Middle Eocene ◽  
Temporal Trends ◽  
Late Eocene ◽  
High Rate ◽  
Mass Extinctions ◽  
Crown Group ◽  
Climatic Effects ◽  
General Decline

The taxonomic diversity of crocodilians (Crocodylia) through the last 100 million years shows a general decline in the number of genera and species to the present day. But this masks a more complex pattern. This is investigated here using a comprehensive database of fossil crocodilians that provides the opportunity to examine spatial and temporal trends, the influence of sampling, and the role of climate in regulating biodiversity.Crown-group crocodilians, comprising the extant families Alligatoridae, Crocodylidae, and Gavialidae, show the following trend: an initial exponential diversification through the Late Cretaceous and Paleocene that is restricted to the Northern Hemisphere until after the K/T boundary; relatively constant diversity from the Paleocene into the middle Eocene that may be an artifact of sampling, which might mask an actual decline in numbers; low diversity during the late Eocene and Oligocene; a second exponential diversification during the Miocene and leveling off in the late Miocene and Pliocene; and a precipitous drop in the Pleistocene and Recent. The coincidence of drops in diversity with global cooling is suggestive of a causal link—during the initial glaciation of Antarctica in the Eocene and Oligocene and the Northern Hemisphere glaciation at the end of the Pliocene. However, matters are complicated in the Northern Hemisphere by the climatic effects of regional uplift.Although the global trend of diversification is unperturbed at the K/T boundary, this is largely due to the exceptionally high rate of origination in the early Paleocene. Nonetheless, the survival of such a demonstrably climate-sensitive group strongly suggests that a climatic explanation for the K/T mass extinctions, especially the demise of the dinosaurs, must be reconsidered.

scholarly journals SOKOLOWIA HORIZON OF THE ZIARAT FORMATION (EASTERN ALBORZ, IRAN): BIOSTRATIGRAPHIC AND PALEOGEOGRAPHIC IMPLICATIONS

2019 ◽  
pp. 15-27
Author(s):  
Mehdi Hadi ◽  
Amir Salahi ◽  
Yaghub Nasiri ◽  
Hossein Mosaddegh
Keyword(s):  
Central Asia ◽  
Tarim Basin ◽  
Genetic Relationship ◽  
Benthic Foraminifera ◽  
Middle Eocene ◽  
Southeastern Europe ◽  
Larger Benthic Foraminifera ◽  
Central Asian ◽  
Apparent Similarity ◽  
Eastern Central Asia

The present study deals with molluscan accumulations of the Sokolowia horizon, which is a key-bed in the middle Eocene of the Kalateh section (Ziarat Formation, Eastern Alborz, Iran). The age of this “key horizon” is at-tributed to Bartonian based on presence of larger benthic foraminifera species such as Nummulites lyelli (D'Archiac & Haime), Orbitoclypeus zitteli (Checchia-Rispoli) and Asterocyclina stella stella (Gümbel) immediately below it. The paleogeographic distribution of Sokolowia occurrence from Tarim Basin in eastern Central Asia to the Transylvanian Basin in southeastern Europe indicates a middle Eocene seaway along the southern margin of an Eurasian epicontinental sea. In particular, the comparison of middle Paleogene sequences in different Central Asian regions reveals an apparent similarity between those basins pointing to their genetic relationship.

Imperforate Larger Benthic Foraminifera from Shallow-water Carbonate Facies (middle and Late Eocene), Zagros Mountains, Iran

2019 ◽  
Vol 49 (3) ◽  
pp. 275-302 ◽  
Author(s):  
Elham Nafarieh ◽  
Carme Boix ◽  
Erzika Cruz-Abad ◽  
Ebrahim Ghasemi-Nejad ◽  
Alireza Tahmasbi ◽  
...  
Keyword(s):  
Shallow Water ◽  
Benthic Foraminifera ◽  
Late Eocene ◽  
Photic Zone ◽  
Zagros Mountains ◽  
Carbonate Facies ◽  
Foraminiferal Assemblage ◽  
Larger Benthic Foraminifera ◽  
Water Carbonate ◽  
Shallow Water Carbonate

Abstract We studied the architecture and biostratigraphical distribution of the imperforate larger benthic foraminifera from the upper part of the Jarhum Formation in the Fars Interior (Zagros, Iran) and identified 15 taxa belonging to the families Coskinolinidae, Orbitolinidae, Austrillinidae, Praerhapydioninidae and Soritidae. This foraminiferal assemblage indicates deposition in warm, shallow (upper photic zone), relatively oligotrophic conditions compatible with an inner-ramp setting. The age attributed to the assemblage is Bartonian-earliest Priabonian.

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