Shallow water agglutinated foraminiferal response to Late Cretaceous–Early Paleocene sea-level changes in the Dakhla Oasis, Western Desert, Egypt

2017 ◽  
Vol 78 ◽  
pp. 240-257 ◽  
Author(s):  
Sreepat Jain ◽  
Sherif Farouk
Keyword(s):  
Shallow Water ◽  
Sea Level ◽  
Late Cretaceous ◽  
Western Desert ◽  
Sea Level Changes ◽  
Early Paleocene ◽  
Dakhla Oasis

Benthic foraminiferal response to relative sea-level changes in the Maastrichtian–Danian succession at the Dakhla Oasis, Western Desert, Egypt

2016 ◽  
Vol 155 (3) ◽  
pp. 729-746 ◽  
Author(s):  
SHERIF FAROUK ◽  
SREEPAT JAIN
Keyword(s):  
Sea Level ◽  
Western Desert ◽  
Level Curve ◽  
Sea Level Changes ◽  
Low Oxygen ◽  
Benthic Environment ◽  
Oxygen Conditions ◽  
Early Paleocene ◽  
Dakhla Oasis ◽  
Regional Tectonics

AbstractThe Maastrichtian–Danian benthic foraminiferal diversity and assemblages through sequence stratigraphy were studied at Dakhla Oasis, Egypt. Benthic foraminifera numbers (BFN), high-flux species and characteristic benthic foraminiferal species and genera distribution are also incorporated to assess palaeobathymetry, palaeoenvironment and palaeoproductivity. All these proxies are then taken together to construct a sea-level curve and interpreted in terms of regional tectonics, climate and eustasy. Data suggest a remarkably highly equitable benthic environment deposited in a brackish littoral and/or marsh setting with moderate (?) to low oxygen conditions and reduced salinity (oligotrophic), possibly due to increased precipitation and terrestrial runoff. The interrupted dominance of calcareous forms and high-organic-flux species suggests occasional marine incursions and high palaeoproductivity, due to local upwelling. The inferred sea-level curve replicates the global eustatic curve and suggests that the curve is more influenced by the prevailing climate and global eustasy rather than by regional tectonics. The post-Cretaceous–Palaeogene boundary displays improvement in the environment in terms of diversity and number of species and specimens, with a marked reduction in the abundance of high-organic-flux species during early Paleocene (Danian) time, indicating a shift from a more mesotrophic open marine environment to much reduced oligotrophic conditions.

scholarly journals Upper Arenig trilobite biostratigraphy and sea-level changes at Lynna River near Volkhov, Russia

2003 ◽  
Vol 50 ◽  
pp. 105-114
Author(s):  
T. Hansen ◽  
A.T. Nielsen
Keyword(s):  
Shallow Water ◽  
Sea Level Rise ◽  
Sea Level ◽  
Abundance Ratio ◽  
Basal Part ◽  
Sea Level Changes ◽  
Faunal Turnover ◽  
Lower Ordovician ◽  
Water Conditions ◽  
Tentative Interpretation

Over 5000 trilobites have been collected from Lower Ordovician rocks exposed at the Lynna River in the Volkhov region, east of St. Petersburg, Russia. Bed-by-bed sampling has been carried out through the upper part of Volkhov Formation (top of Jeltiaki Member and the entire Frizy Member), the Lynna Formation and the basal part of the Obukhovo Formation. This interval, which is 7.5 metres thick, correlates with the upper part of the Arenig Series, and presumably even ranges into the very base of the Llanvirn. A preliminary biostratigraphical investigation of top Jeltiaki Member (BIIβ), Frizy Member (BIIγ) and basal Lynna Formation (BIIIα) reveals a rather continuous faunal turnover lacking sharp boundaries, and the biostratigraphical zonation (BIIβ–BIIIα) is primarily defined by the index trilobite taxa. The trilobite ranges are generally in agreement with the pattern described by Schmidt in 1907. The abundance ratio between Asaphus and the ptychopygids seems to be related to changes in relative sea level with Asaphus preferring the most shallow water conditions. A tentative interpretation of sea-level changes suggests an initial drowning at the base of BIIγ, immediately followed by a lowstand that in turn was succeeded by a moderate sea-level rise and then a significant fall. The last marks the BIIγ/BIIIα boundary. Correlation with sections in Scandinavia suggests that the basal part of BIIγ is strongly condensed.

scholarly journals Short-Term Sea Level Changes of the Upper Cretaceous Carbonates: Calibration between Palynomorphs Composition, Inorganic Geochemistry, and Stable Isotopes

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1099
Author(s):  
Ahmed Mansour ◽  
Thomas Gentzis ◽  
Michael Wagreich ◽  
Sameh S. Tahoun ◽  
Ashraf M.T. Elewa
Keyword(s):  
Sea Level ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Freshwater Algae ◽  
Sea Level Changes ◽  
Short Term ◽  
Sea Level Oscillations ◽  
Rising Sea Level ◽  
Southern Tethys

Widespread deposition of pelagic-hemipelagic sediments provide an archive for the Late Cretaceous greenhouse that triggered sea level oscillations. Global distribution of dinoflagellate cysts (dinocysts) exhibited a comparable pattern to the eustatic sea level, and thus, considered reliable indicators for sea level and sequence stratigraphic reconstructions. Highly diverse assemblage of marine palynomorphs along with elemental proxies that relate to carbonates and siliciclastics and bulk carbonate δ13C and δ18O from the Upper Cretaceous Abu Roash A Member were used to reconstruct short-term sea level oscillations in the Abu Gharadig Basin, southern Tethys. Additionally, we investigated the relationship between various palynological, elemental, and isotope geochemistry parameters and their response to sea level changes and examined the link between these sea level changes and Late Cretaceous climate. This multiproxy approach revealed that a long-term sea-level rise, interrupted by minor short-term fall, was prevalent during the Coniacian-earliest Campanian in the southern Tethys, which allowed to divide the studied succession into four complete and two incomplete 3rd order transgressive-regressive sequences. Carbon and oxygen isotopes of bulk hemipelagic carbonates were calibrated with gonyaulacoids and freshwater algae (FWA)-pteridophyte spores and results showed that positive δ13Ccarb trends were consistent, in part, with excess gonyaulacoid dinocysts and reduced FWA-spores, reinforcing a rising sea level and vice versa. A reverse pattern was shown between the δ18Ocarb and gonyaulacoid dinocysts, where negative δ18Ocarb trends were slightly consistent with enhanced gonyaulacoid content, indicating a rising sea level and vice versa. However, stable isotope trends were not in agreement with palynological calibrations at some intervals. Therefore, the isotope records can be used as reliable indicators for reconstructing changes in long-term sea level rather than short-term oscillations.

Maastrichtian to early Paleocene sea level changes and climatic evolution on the southeastern Tethys margin

2019 ◽  
Vol 100 ◽  
pp. 285-296 ◽  
Author(s):  
Ibtisam Beik ◽  
Thierry Adatte ◽  
Olaf G. Podlaha ◽  
Jörg Mutterlose
Keyword(s):  
Sea Level ◽  
Sea Level Changes ◽  
Early Paleocene ◽  
Climatic Evolution

scholarly journals Paleozoic–Mesozoic Eustatic Changes and Mass Extinctions: New Insights from Event Interpretation

Life ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 281
Author(s):  
Dmitry A. Ruban
Keyword(s):  
Sea Level ◽  
Late Cretaceous ◽  
Mass Extinction ◽  
Early Jurassic ◽  
Late Devonian ◽  
Mass Extinctions ◽  
Sea Level Changes ◽  
Event Interpretation ◽  
Marine Realm ◽  
Global Sea Level

Recent eustatic reconstructions allow for reconsidering the relationships between the fifteen Paleozoic–Mesozoic mass extinctions (mid-Cambrian, end-Ordovician, Llandovery/Wenlock, Late Devonian, Devonian/Carboniferous, mid-Carboniferous, end-Guadalupian, end-Permian, two mid-Triassic, end-Triassic, Early Jurassic, Jurassic/Cretaceous, Late Cretaceous, and end-Cretaceous extinctions) and global sea-level changes. The relationships between eustatic rises/falls and period-long eustatic trends are examined. Many eustatic events at the mass extinction intervals were not anomalous. Nonetheless, the majority of the considered mass extinctions coincided with either interruptions or changes in the ongoing eustatic trends. It cannot be excluded that such interruptions and changes could have facilitated or even triggered biodiversity losses in the marine realm.

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