scholarly journals Paleogene calcareous nannoplankton evolution: the fertility link

1992 ◽  
Vol 6 ◽  
pp. 12-12
Author(s):  
Marie-Pierre Aubry
Keyword(s):  
Middle Eocene ◽  
Trophic Levels ◽  
Vertical Stratification ◽  
Moderate Increase ◽  
Photic Zone ◽  
Calcareous Nannoplankton ◽  
Calcareous Nannofossil ◽  
Biogeographic Patterns ◽  
Early Oligocene ◽  
Late Paleocene

Calcareous nannoplankton diversity varied greatly during the Paleogene. From extremely reduced values (~10 species) in the early Paleocene (circa 66.4 to 66 Ma, age estimates from Berggren, Kent and Flynn, 1985) following the terminal Cretaceous extinctions, diversity increased progressively throughout the late Paleocene and early Eocene and reached a maximum (~120 species) in the early middle Eocene (circa 52–48 Ma). This was followed by a step-like decrease until the early Oligocene (circa 35 Ma) when minimal values (~37 species) were reached once again. After a stable low during the remainder of the early Oligocene, a moderate, increase occurred near the early/late Oligocene boundary (circa 30 Ma).Temperature has been regarded as the most important factor controlling the distribution of the calcareous nannoplankton following the characterisation of five temperature-controlled assemblages of living Coccolithophoridae in the Atlantic Ocean. Studies relative to variations in diversity in the calcareous nannoplankton throughout the Mesozoic and Cenozoic and among the extinct late Paleocene to Pliocene group Discoaster, and to changing biogeographic patterns during the Cenozoic have revealed an apparent relationship between composition of calcareous nannofossil assemblages and temperature as deduced from isotopic studies. This relationship, which is currently used to infer Paleogene climatic and oceanographic evolution from quantitative analyses of calcareous nannofossil assemblages, is however not a simple one as indicated by the fact that maximum diversity during the Paleogene (i.e., the early middle Eocene) did not occur during (but subsequently to) the warmest time (i.e., the latest Paleocene-earliest Eocene).Diversity changes in the Paleogene calcareous nannoplankton are strikingly similar to diversity changes in the Paleogene planktonic foraminifera, which have been shown to reflect fluctuations in nutrient availibility as indicated by oxygen and carbon isotopes. The parallel evolution in the two groups thus suggests that trophic levels in the photic zone played an important role in the Paleogene diversification of the calcareous nannoplankton. In the present day ocean, the calcareous nannoplankton (Coccolithophoridae) dominate the phytoplankton under oligotrophic conditions and tropical waters are characterized by highly diversified associations with strong vertical specific stratification. Only few species occur under meso- and eutrophic conditions, and there is no vertical stratification. Extremely low diversity during the earliest Paleocene followed by increasing diversity through the Paleocene and earliest Eocene is interpreted as reflecting the change from an essentially mesotrophic to an oligotrophic ocean, increased rates of speciation resulting from niche partitioning occasioned by increased oligotrophy, leading to strong vertical stratification of species in the photic zone. Decrease in diversity from middle Eocene to early Oligocene reflects, on the other hand, progressive eutrophication of the ocean as a result of climatic deterioration.

Palynological characteristic of the border cretaceous and paleogene deposits in the Sourth of Trans-Ural region (bh 9, Troizk)

2020 ◽  
Author(s):  
Olga B. Kuzmina ◽  
◽  
Natalia K. Lebedeva ◽  
Keyword(s):  
Upper Cretaceous ◽  
Western Siberia ◽  
Middle Eocene ◽  
Ural Region ◽  
The South ◽  
Spores And Pollen ◽  
Early Oligocene ◽  
Late Paleocene

The Upper Cretaceous and Paleogene sediments exposed in Borehole 9 (Troizk, Chelyabinsk Area) in the south of the Trans-Ural Region (Western Siberia) are studied by palynological methods. The BH9 has uncovered the Fadyushinskaya and Gan’kino formations of Upper Cretacious age and the Talitsa, Serov, Irbit, Chegan and Kurtamysh formations of Paleogene age. Nine dinocysts assemblages and nine spores and pollen assemblages were revealed. The Campanian, Maastrichtian, Late Paleocene, Low-Middle Eocene and Early Oligocene age of the sediments were substantiated.

scholarly journals Preface to 'Evolution, Extinction and Biogeography in Gondwana'

2001 ◽  
Vol 49 (3) ◽  
pp. I
Author(s):  
Robert S. Hill
Keyword(s):  
Middle Eocene ◽  
Long Distance ◽  
Plant Family ◽  
Widespread Distribution ◽  
Early Oligocene ◽  
Vegetation Disturbance ◽  
Late Paleocene ◽  
The Family ◽  
Dispersal Events ◽  
Early Cenozoic

The macrofossil record of the plant family Cunoniaceae in Australia is summarised and reviewed where necessary by using detailed studies of the morphology of extant genera. Eleven of the 26 Cunoniaceae genera are represented in the Australian macrofossil record and include leaves and leaf fragments, foliar cuticle and reproductive structures, and range from Late Paleocene to Quaternary in age. Macrofossils show that some genera had a different or more widespread distribution in Australia during the Cenozoic, with two genera (Weinmannia and Codia) having become extinct from the continent. Changes in climate, including increasing cold, frost, dryness, seasonality, or some combination of these, or a reduction in vegetation disturbance regimes (e.g. volcanism, uplifting, landslips), may be implicated in the regional or continental extinctions demonstrated by the macrofossil record. Many extant genera (Schizomeria, Vesselowskya, Callicoma, Ceratopetalum, Acsmithia, Codia) had evolved by the Early Oligocene or earlier (Eucryphia, Late Paleocene; Ceratopetalum, Middle Eocene), perhaps with generic diversification more or less complete by the end of the Early Cenozoic or earlier. A Cretaceous origin of the family is possible, and may account for its widespread distribution on Southern Hemisphere landmasses, although long-distance dispersal events are required to explain some modern geographic disjunctions.

scholarly journals Reworked nannofossils from the Lower Miocene deposits in the Magura Nappe (Outer Western Carpathians, Poland)

2012 ◽  
Vol 63 (5) ◽  
pp. 407-424 ◽  
Author(s):  
Marta Oszczypko-Clowes
Keyword(s):  
Middle Eocene ◽  
Late Eocene ◽  
Calcareous Nannofossils ◽  
Late Oligocene ◽  
Calcareous Nannoplankton ◽  
Lower Miocene ◽  
Early Oligocene ◽  
Quantitative Studies ◽  
Outer Western Carpathians ◽  
Quantitative Analyses

Abstract Studies, based on calcareous nannofossils, proved that the level of reworked microfossils had so far been underestimated. More recently detailed quantitative studies of calcareous nannoplankton of the Magura, Malcov, Zawada and Kremna formations from the Magura Nappe in Poland documented a degree of nannofossil recycling among those formations. In the Late Eocene-Early Oligocene pelagic Leluchów Marl Member of the Malcov Formation the level of redeposition is very low (0-3.80 %), however, in the flysch deposits of the Malcov Formation reworking increased to 31.4 %. Late Oligocene through Early Miocene “molasse” type deposits of the Zawada and Kremna formations contain 43.7-69.0 % of reworked nannofossils. Quantitative analyses of the reworked assemblages confirmed the domination of Paleogene nannofossil species over Cretaceous ones. The most abundant, reworked assemblages belong to the Early- Middle Eocene age.

The history of Cunoniaceae in Australia from macrofossil evidence

2001 ◽  
Vol 49 (3) ◽  
pp. 301 ◽  
Author(s):  
Richard W. Barnes ◽  
Robert S. Hill ◽  
Jason C. Bradford
Keyword(s):  
Middle Eocene ◽  
Long Distance ◽  
Widespread Distribution ◽  
Early Oligocene ◽  
Vegetation Disturbance ◽  
Late Paleocene ◽  
The Family ◽  
History Of ◽  
Dispersal Events ◽  
Early Cenozoic

The macrofossil record of the plant family Cunoniaceae in Australia is summarised and reviewed where necessary by using detailed studies of the morphology of extant genera. Eleven of the 26 Cunoniaceae genera are represented in the Australian macrofossil record and include leaves and leaf fragments, foliar cuticle and reproductive structures, and range from Late Paleocene to Quaternary in age. Macrofossils show that some genera had a different or more widespread distribution in Australia during the Cenozoic, with two genera (Weinmannia and Codia) having become extinct from the continent. Changes in climate, including increasing cold, frost, dryness, seasonality, or some combination of these, or a reduction in vegetation disturbance regimes (e.g. volcanism, uplifting, landslips), may be implicated in the regional or continental extinctions demonstrated by the macrofossil record. Many extant genera (Schizomeria, Vesselowskya, Callicoma, Ceratopetalum, Acsmithia, Codia) had evolved by the Early Oligocene or earlier (Eucryphia, Late Paleocene; Ceratopetalum, Middle Eocene), perhaps with generic diversification more or less complete by the end of the Early Cenozoic or earlier. A Cretaceous origin of the family is possible, and may account for its widespread distribution on Southern Hemisphere landmasses, although long-distance dispersal events are required to explain some modern geographic disjunctions.

scholarly journals Calcareous nannofossil assemblage changes from early to middle Eocene in the Levant margin of the Tethys, central Israel

2011 ◽  
Vol 30 (2) ◽  
pp. 129-139 ◽  
Author(s):  
Menahem Weinbaum-Hefetz ◽  
Chaim Benjamini
Keyword(s):  
Middle Eocene ◽  
Middle Part ◽  
Early Eocene ◽  
Calcareous Nannoplankton ◽  
Calcareous Nannofossil ◽  
Cooling Process ◽  
Plateau Central ◽  
Biotic Change ◽  
Levant Margin ◽  
Prominent Peak

Abstract. Patterns of change in calcareous nannofossil assemblages during nannozones NP11 to NP16 on the southern Levant margin of the Tethys were observed from sections of early and middle Eocene age sediments of the Avedat Plateau, central Israel. A cooling process following the Early Eocene Climate Optimum (EECO) is supported by several events of biotic change over a 4 Ma interval. The rate of pelagic sedimentation varied from 7.5 at the EECO to 23.6 m Ma–1 at the cooling transition phase. Reduced numbers of discoasters mark the end of the oligotrophic regime within the NP13 nannozone, followed by an increase in nannofossil richness especially marked by Blackites and Chiasmolithus spp. In the middle part of the cooling process a prominent peak of reworked Paleocene taxa, up to 7% of total taxa, suggests that enhanced current activity caused re-sedimentation on the Levant margin slopes. When stability resumed in the upper part of the NP15–16 interval, Coccolithus-type placoliths became rare and Reticulofenestra-type forms became dominant. Calcareous nannoplankton response to this gradual cooling became irreversible in the late Palaeogene, but the change was, however, diachronous across the Tethys.

scholarly journals The Cenozoic Malaguide Basin from Sierra Espuña (Murcia, S Spain): An Example of Geological Heritage

Geosciences ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Santiago Moliner-Aznar ◽  
Manuel Martín-Martín ◽  
Tomás Rodríguez-Estrella ◽  
Gregorio Romero-Sánchez
Keyword(s):  
Middle Eocene ◽  
Geological Heritage ◽  
Passive Margin ◽  
Early Miocene ◽  
Late Oligocene ◽  
Deep Basin ◽  
Sedimentary Evolution ◽  
Early Oligocene ◽  
Upper Oligocene ◽  
Very High

The Cenozoic Malaguide Basin from Sierra Espuña (Internal Betic Zone, S Spain) due to the quality of outcropping, areal representation, and continuity in the sedimentation can be considered a key-basin. In the last 30 years, a large number of studies with very different methodological approaches have been done in the area. Models indicate an evolution from passive margin to wedge-top basin from Late Cretaceous to Early Miocene. Sedimentation changes from limestone platforms with scarce terrigenous inputs, during the Paleocene to Early Oligocene, to the deep basin with huge supplies of turbidite sandstones and conglomerates during the Late Oligocene to Early Miocene. The area now appears structured as an antiformal stack with evidence of synsedimentary tectonics. The Cenozoic tectono-sedimentary basin evolution is related to three phases: (1) flexural tectonics during most of the Paleogene times to create the basin; (2) fault and fold compartmentation of the basin with the creation of structural highs and subsiding areas related to blind-fault-propagation folds, deforming the basin from south to north during Late Oligocene to Early Aquitanian times; (3) thin-skin thrusting tectonics when the basin began to be eroded during the Late Aquitanian-Burdigalian. In recent times some works on the geological heritage of the area have been performed trying to diffuse different geological aspects of the sector to the general public. A review of the studies performed and the revisiting of the area allow proposing different key-outcrops to follow the tectono-sedimentary evolution of the Cenozoic basin from this area. Eight sites of geological interest have been selected (Cretaceous-Cenozoic boundary, Paleocene Mula Fm, Lower Eocene Espuña-Valdelaparra Fms, Middle Eocene Malvariche-Cánovas Fms, Lowermost Oligocene As Fm, Upper Oligocene-Lower Aquitanian Bosque Fm, Upper Oligocene-Aquitanian Río Pliego Fm, Burdigalian El Niño Fm) and an evaluation has been performed to obtain four parameters: the scientific value, the educational and touristic potential, and the degradation risk. The firsts three parameters obtained values above 50 being considered of “high” or “very high” interest (“very high” in most of the cases). The last parameter shows always values below 50 indicating a “moderate” or “low” risk of degradation. The obtained values allow us considering the tectono-sedimentary evolution of this basin worthy of being proposed as a geological heritage.

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