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.

Tremadocian (Lower Ordovician) sea-level changes and biotas on the Avalon microcontinent

2011 ◽  
Vol 85 (4) ◽  
pp. 678-694 ◽  
Author(s):  
ED Landing ◽  
Richard A. Fortey
Keyword(s):  
Sea Level ◽  
Sea Level Changes ◽  
Low Oxygen ◽  
Cape Breton Island ◽  
Lower Upper ◽  
The North ◽  
Cape Breton ◽  
Lower Ordovician ◽  
Bottom Waters ◽  
History Of

The Chesley Drive Group, an Upper Cambrian-Lower Ordovician mudstone-dominated unit, is part of the Ediacaran–Ordovician cover sequence on the North American part of the Avalon microcontinent. The upper Chesley Drive Group on McLeod Brook, Cape Breton Island (previously “McLeod Brook Formation”), has two lithofacies-specific Tremadocian biotas. An older low-diversity benthic assemblage (shallow burrowers, Bathysiphon, phosphatic brachiopods, asaphid trilobites) is in lower upper Tremadocian green-gray mudstone. This wave-influenced, slightly dysoxic facies has Bathysiphon–brachiopod shell lags in ripple troughs. The upper fauna (ca. 483 +/- 1 Ma) is in dysoxic-anoxic (d-a), unburrowed, dark gray-black, upper upper (but not uppermost) Tremadocian mudstone with a “mass kill” of the olenid Peltocare rotundifrons (Matthew)—a provincial trilobite in Avalonian North America that likely tolerated low oxygen bottom waters. Scandodus avalonensis Landing n. sp. and Lagenochitina aff. conifundus (Poumot), probable nektic elements and the first upper Tremadocian conodont and chitinozoan reported from Avalon, occur in diagenetic calcareous nodules in the dark gray-black mudstone. An upper Tremadocian transition from lower greenish to upper black mudstone is not exposed on McLeod Brook, but is comparable to a coeval green-black mudstone transition in Avalonian England. The successions suggest that late late Tremadocian (probable Baltic Hunnebergian Age) sea level was higher in Avalon than is suggested from successions on other paleocontinents. The Tremadocian sea-level history of Avalon was a shoaling-deepening-shoaling sequence from d-a black mudstone (lower Tremadocian), to dysoxic green mudstone (lower upper Tremadocian), and back to black mudstone (upper upper Tremadocian).Scandodus Lindström is emended, with the early species S. avalonensis Landing n. sp. assigned to the emended Family Protopanderodontidae. Triangulodus Van Wamel is considered a junior synonym of Scandodus. Peltocare rotundifrons is emended on the basis of complete specimens.

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

A link in the chain of the Cambrian zooplankton: bradoriid arthropods invade the water column

2015 ◽  
Vol 152 (5) ◽  
pp. 923-934 ◽  
Author(s):  
MARK WILLIAMS ◽  
THIJS R. A. VANDENBROUCKE ◽  
VINCENT PERRIER ◽  
DAVID J. SIVETER ◽  
THOMAS SERVAIS
Keyword(s):  
Sea Level Rise ◽  
Water Column ◽  
Sea Level ◽  
Global Distribution ◽  
Geographical Range ◽  
Low Oxygen ◽  
Active Lifestyle ◽  
Environmental Controls ◽  
Continental Shelves ◽  
Oxygen Conditions

AbstractBradoriids are small bivalved arthropods that had global distribution for about 20 million years beginning at Cambrian Epoch 2 (c. 521 Ma). The majority of bradoriids are considered to be benthic, favouring oxygenated waters, as suggested by their anatomy, lithofacies distribution, faunal associates and provinciality. Most bradoriids were extinct by the end of the Drumian Age (middle of Cambrian Epoch 3). The post-Drumian is characterized by widespread dysoxic shelf lithofacies in southern Britain and Scandinavia and by the abundance of phosphatocopid arthropods. This interval is also associated with two bradoriid species with wide intercontinental distribution: Anabarochilina primordialis, which had a geographical range from the palaeo-tropics to high southern palaeo-latitude, and Anabarochilina australis, which extended through the palaeo-tropics from Laurentia to Gondwana. The wide environmental and geographical range of these species, coupled with a carapace anatomy that suggests an active lifestyle, is used to infer a zooplanktonic lifestyle. A possible driver of this widespread Cambrian bradoriid zooplankton was sea-level rise coupled to the periodic spread of low oxygen conditions onto continental shelves, acting in tandem with anatomical pre-adaptations for swimming. Parallels exist with the myodocope ostracod colonization of the water column during Silurian time, which may also have been influenced by extrinsic environmental controls acting on anatomical pre-adaptations for swimming. Similar biological and environmental mechanisms may have facilitated arthropod zooplankton colonizations across Phanerozoic time.

Arenigian (Early Ordovician) sea-level history and the response of conodont communities, western Newfoundland

2004 ◽  
Vol 41 (7) ◽  
pp. 843-865 ◽  
Author(s):  
Shunxin Zhang ◽  
Christopher R Barnes
Keyword(s):  
Sea Level ◽  
Environmental Gradient ◽  
Sea Level Change ◽  
Level Curve ◽  
Sea Level Changes ◽  
Baltic Region ◽  
Level Change ◽  
Lower Ordovician ◽  
Central Australia ◽  
The Baltic

Four cluster analyses were performed, which recognized 17 conodont communities in the Arenigian (Lower Ordovician) of western Newfoundland. The analyses include 69 598 identifiable conodont specimens recovered from 153 conodont-bearing samples from four stratigraphical sections representing the environmental settings of the platform, upper proximal slope, lower proximal slope, and distal slope. The distribution of conodont communities along the platform to slope environmental gradient shows that sea-level changes simultaneously affected the development and replacement of the conodont communities in the different facies. The pattern of change in conodont communities allows an interpretation of sea-level change that is correlated precisely into the detailed graptolite biozonation. A gradual transgression lasted most of Tetragraptus approximatus Zone time, which was followed by a brief regression; a transgression–regression cycle occurred in the T. akzharensis Zone time; a major transgression caused a highstand during the entire Pendeograptus fruticosus Zone time, which was followed by a major regression in the early Didymograptus bifidus Zone time; Isograptus victoriae lunatus Zone time included repetitive oscillations of sea level; a severe regression in the earliest I. i. victoriae Zone time was represented by the St. George unconformity on the platform and the Bed 12 megaconglomerate on the slope, reaching the lowest sea level during the I. i. maximus Zone time. The Arenigian sea-level curve developed by this study only partly agrees with that from the Baltic region and central Australia based on trilobite communities.

Late-Quaternary Sea Level Changes, Umnak Island, Aleutians—Their Effects on Ancient Aleuts and their Causes

1974 ◽  
Vol 4 (3) ◽  
pp. 264-281 ◽  
Author(s):  
Robert F. Black
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Food Resources ◽  
Aleutian Islands ◽  
Level Curve ◽  
Present Position ◽  
Present Level ◽  
Sea Level Changes ◽  
Relative Sea Level

Late-Quaternary sea level changes in the eastern Aleutian Islands are of paramount importance in the reconstruction of the migrations and environment of the ancient Aleuts. A radiocarbon-dated ash stratigraphy provides the chronology into which geomorphic events can be fitted. These provide evidence for the sea level changes. Deployment of beach material and coastal configuration intimate that sea level was about 2–3 m above the present level about 8250 radiocarbon yr BP. Beach deposits suggest that sea level remained high until about 3000 radiocarbon y.a. when it gradually dropped to its present position. It is concluded that the ancient Aleuts that settled Anangula about 8400 y.a. used boats; all major passes in the eastern Aleutians were flooded, and did not have winter ice. Those ancient Aleuts did not have available the major year-around food resources of the present strandflats as they were cut during the high sea level stand 8250–3000 yr BP. The ancient Aleuts must have been marine oriented, for land-based food resources would have been limited.The cause of relative sea level changes on Umnak Island is considered indeterminate with present data. Eustatic, glacial isostatic, water isostatic, tectonic, and volcanic causes are considered the main possible controls in combinations such that a basic eustatic sea level curve and likely a glacial-water isostatic curve must be common to any solution. Representative solutions are given to illustrate some of the problems.

Deep-sea ostracod faunal dynamics in a marginal sea: biotic response to oxygen variability and mid-Pleistocene global changes

Paleobiology ◽  
2018 ◽  
Vol 45 (1) ◽  
pp. 85-97 ◽  
Author(s):  
Huai-Hsuan May Huang ◽  
Moriaki Yasuhara ◽  
Hokuto Iwatani ◽  
Tatsuhiko Yamaguchi ◽  
Katsura Yamada ◽  
...  
Keyword(s):  
Sea Level ◽  
Sea Of Japan ◽  
Deep Sea ◽  
The Sea Of Japan ◽  
Global Changes ◽  
Sea Level Changes ◽  
Low Oxygen ◽  
Migration Ability ◽  
Sea Level Fluctuations ◽  
Benthic Ecosystems

AbstractDeep-sea benthic ostracod assemblages covering the last 2 Myr were investigated in Integrated Ocean Drilling Program Site U1426 (at 903 m water depth) in the southern Sea of Japan. Results show that (1) orbital-scale faunal variability has been influenced by eustatic sea-level fluctuations and oxygen variability and (2) secular-scale faunal transitions are likely associated with the mid-Brunhes event (MBE, ~0.43 Ma) and the onset of the Tsushima Warm Current (TWC, ~1.7 Ma).Krithe,Robertsonites, andAcanthocythereisare the three most abundant genera throughout the core, accounting for 78.5% of total specimens. Multiple-regression tree analysis indicated that the TWC, the MBE, and oxygen content are the significant controlling factors of ostracod dominance. Changes in assemblages exhibit decline and recovery patterns corresponding to orbital-scale cyclicity of sea-level changes. In the Sea of Japan marginal ocean setting, this cyclicity shows a close relationship with bottom-water oxygen variability since the onset of the TWC influx. The MBE amplified the influence of the TWC and oxygen variability to the deep-sea ecosystem through larger sea-level fluctuations.Acanthocythereis dunelmensis, a circumpolar species, dominates before the TWC onset. After the TWC onset and during the mid-Pleistocene transition (MPT, ~1.2–0.7 Ma)Krithespp., known for their low-oxygen tolerance, substantially increase under moderate oxygen depletion. At the end of the MPT,Krithedominance diminishes and is replaced byRobertsonites hanaiiandPropontocyprisspp. after the MBE. The post-MBE assemblage, characterized byR. hanaii, suggests a slightly warmer environment under the development of the TWC. In addition, the post-MBE high-amplitude climate system may have caused the increased abundance of active-swimmingPropontocyprisspp. due to their superior migration ability. Benthic ecosystems in marginal seas are sensitive and vulnerable to both short- and long-term climatic changes, and the MBE is suggested to be a global biotic event affecting benthic ecosystems substantially.

Sign in / Sign up

Export Citation Format

Share Document