Early Miocene carbonate depositional environments, East Java Sea

2018 ◽  
Author(s):  
C.S. Kenyon
Keyword(s):  
Depositional Environments ◽  
Early Miocene ◽  
Java Sea

scholarly journals Sedimentology and fossil vertebrates of the Santa Cruz Formation (early Miocene) in Lago Posadas, southwestern Patagonia, Argentina

2019 ◽  
Vol 46 (2) ◽  
pp. 383
Author(s):  
José I. Cuitiño ◽  
Sergio F. Vizcaíno ◽  
M. Susana Bargo ◽  
Inés Aramendía
Keyword(s):  
Depositional Environments ◽  
Sediment Supply ◽  
Early Miocene ◽  
Primary Control ◽  
Santa Cruz ◽  
Basin Subsidence ◽  
Secondary Consumers ◽  
Fossil Vertebrate ◽  
Sandstone Composition ◽  
Patagonian Andes

Lago Posadas is located at the foot of the Southern Patagonian Andes, in southwestern Argentina, where the early Miocene Santa Cruz Formation (SCF) shows thick and laterally continuous exposures. This region has been scarcely explored for fossil vertebrates since the first efforts by J.B. Hatcher in 1898-99. In this contribution, we performed sedimentologic and paleontological studies in order to reconstruct depositional environments and the associated fossil vertebrate fauna. Sedimentologic data suggest that the sedimentary record begins with restricted marine-estuarine deposits grading upward to fluvial floodplains and fluvial channels. Extensive floodplains, occasionally interrupted by low-sinuosity, sand-dominated channels, show dominant reddish coloration, moderate to low paleosol development, abundant crevasse splay sandstones and lack of vegetal remains, suggesting deposition in a low gradient, oxygenated setting under elevated sedimentation rates. Vertical stratigraphic trends are subtle, suggesting little paleoenvironmental changes during deposition of the whole SCF in this region. Paleocurrent directions, sandstone composition and paleogeographic reconstructions all indicate that deposition of the SCF was strongly associated to the contemporaneous uplift of the Andes. Fossil vertebrates analyzed are the result of our collecting effort and revision of museum collections. The faunal assemblage includes 31 taxa: 28 mammals and three birds. Mammals belong to the main groups recorded in other areas of the SCF (metatherians, xenarthrans, notoungulates, litopterns, astrapotheres and rodents). The assemblage allows a Santacrucian Age sensu lato assignment for the fauna at Lago Posadas. Taxonomic revisions of several taxa are necessary to further adjust the biostratigraphic significance of this association. The combined record of arboreal, browser and frugivores, on one side, and grazer mammals and rheas, on the other, suggest the presence of both trees and open environments. Frugivores, among primary consumers, and the secondary consumers guild are under-represented due to sample and fossil remain size biases. The sedimentologic and paleontological record of the SCF in Lago Posadas suggests that the uplift of the Southern Patagonian Andes acted as a primary control on basin subsidence and sediment supply, providing a special signature for sub-andean localities. However, previously registered climatic changes are poorly recorded in this study.

Biostratigraphically constrained Neogene palaeoenvironments of the Red Sea rift

2021 ◽  
Author(s):  
Geraint Hughes ◽  
Osman Varol
Keyword(s):  
Sea Level ◽  
Red Sea ◽  
Debris Flows ◽  
Middle Miocene ◽  
Depositional Environments ◽  
Early Miocene ◽  
Arabian Plate ◽  
Tectonic Activity ◽  
Gulf Of Suez ◽  
Gulf Of Aden

<p>Marine sediments deposited in response to the Neogene opening of the Red Sea during divergence of the African-Arabian plate margin provide micropalaeontological chronological evidence to calibrate synchronous palaeoenvironmental events from the Gulf of Suez to the Gulf of Aden. This facility provides insights to the timing and relative rates of tectonic subsidence associated with the rifting episodes of the region. Biostratigraphic index forms include planktonic and benthonic foraminifera and calcareous nannofossils. These, combined with various associated microfossils and macrofossil fragments, permit interpretation of a range of depositional environments that span intertidal to bathyal regimes. Onset and recovery from various hypersaline events are similarly interpreted by integrating microfossils and lithology. Following an episode of emergence and sporadic volcanicity, subsidence and the first Neogene marine transgression created brackish to shallow marine lagoons during the Early Miocene (Foraminiferal Letter Stage Upper Te). Rapid subsidence and accumulation of deep marine mudstones, of local hydrocarbon source-rock quality, with thinly interbedded siliciclastic and calciclastic debris flows commenced in the Early Miocene (Planktonic foraminiferal zones N5-N8; Nannofossil zones NN3-NN5). The debris flows increased in abundance and provide good hydrocarbon reservoirs. The Gulf of Suez and Red Sea experienced episodic isolation from the Indian Ocean during the latest Early Miocene and earliest Middle Miocene (Planktonic foraminiferal zones N8-N9; Nannofossil zone NN5 Foraminiferal Letter Stage Middle-Upper Tf1), resulting in hypersaline events with precipitation of submarine gypsum and halite. The isolation is attributed to constriction of the southern Red Sea, in the vicinity of the Bab El Mandab Straits, by eustatic sea level fall as well as probable tectonic activity; the synchronous Gulf of Aden succession does not display evidence for such hypersaline events. A prolonged hypersaline phase extended over most of the Middle Miocene, for which absence of biostratigraphic data precludes age control. During the latest Middle Miocene to Late Miocene, rejuvenation of the hinterland cause rapid deposition of terrestrial and fluviatile coarse and fine siliciclastics, with similar biostratigraphic paucity except for rare diatoms and palynomorphs. Renewed subsidence, associated with opening of the Aqaba Fault, combined with eustatic sea level rise caused marine deposition to recommence in the Pliocene.</p>

scholarly journals Sedimentary facies, depositional environments and conceptual outcrop analogue (Dam Formation, early Miocene) Eastern Arabian Platform, Saudi Arabia: a new high-resolution approach

2021 ◽  
Vol 11 (6) ◽  
pp. 2497-2518
Author(s):  
Syed Haroon Ali ◽  
Osman M. Abdullatif ◽  
Lamidi O. Babalola ◽  
Fawwaz M. Alkhaldi ◽  
Yasir Bashir ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
High Resolution ◽  
Sea Level ◽  
Depositional Environments ◽  
Early Miocene ◽  
Arabian Plate ◽  
Relative Sea Level ◽  
Thin Sections ◽  
Mixed Carbonate ◽  
Arabian Platform

AbstractThis paper presents the facies and depositional environment of the early Miocene Dam Formation, Eastern Arabian platform, Saudi Arabia. Deposition of Dam Formation (Fm.) was considered as a restricted shallow marine deposition. Few studies suggest the role of sea-level change in its deposition but were without decisive substantiation. Here, we describe the facies and high-resolution model of Dam Fm. under varying depositional conditions. The depositional conditions were subjected to changing relative sea level and tectonics. High-resolution outcrop photographs, sedimentological logs, and thin sections present that the mixed carbonate–siliciclastic sequence was affected by a regional tectonics. The lower part of Dam Fm. presents the development of carbonate ramp conditions that are represented by limestones and marl. The depositional conditions fluctuated with the fall of sea level, and uplift in the region pushed the siliciclastic down-dip and covered the whole platform. The subsequent rise in sea level was not as pronounced and thus allowed the deposition of microbial laminites and stromatolitic facies. The southeast outcrops, down-dip, are more carbonate prone as compared to the northwest outcrop, which allowed the deposition of siliciclastic-prone sedimentation up-dip. All facies, architecture, heterogeneity, and deposition were controlled by tectonic events including uplift, subsidence, tilting, and syn-sedimentary faulting, consequently affecting relative sea level. The resulting conceptual outcrop model would help to improve our understanding of mixed carbonate–siliciclastic systems and serve as an analogue for other stratigraphic units in the Arabian plate and region. Our results show that Dam Fm. can be a good target for exploration in the Northern Arabian Gulf.

Age and Depositional Environments of Tertiary Rocks of Nootka Island, British Columbia (92-E): Mollusks Versus Foraminifers

1973 ◽  
Vol 10 (3) ◽  
pp. 331-365 ◽  
Author(s):  
J. A. Jeletzky
Keyword(s):  
Vancouver Island ◽  
Late Eocene ◽  
Middle Part ◽  
Depositional Environments ◽  
Early Miocene ◽  
Western Coast ◽  
Lower Miocene ◽  
Stratigraphic Position ◽  
The Rich ◽  
Latest Eocene

Conflicting interpretations of age and depositional environment of the Tertiary rocks of Nootka Island and adjacent areas of Vancouver Island resulting from studies of their molluskan and foraminiferal faunas appear to be caused by:1. A conflict of opinion concerning the correlation of regional molluskan, foraminiferal, and mammalian stages now applied to the Tertiary rocks of Western North America with units of the international biochronological standard based on the European faunas and type sections.2. Underestimation of the regional (i.e. within individual regions of the Western North American Tertiary province) biochronological value of Tertiary mollusks and other invertebrate macrofossils by many foraminiferal specialists.3. Neglect of mollusks as paleoecological indices by some foraminiferal specialists.4. Misinterpretation of paleoecological value of fossil foraminifers by some foraminiferal specialists. The application of general considerations 1 to 4 to the Tertiary rocks of Nootka Island and adjacent areas of Vancouver Island indicates that:1. A micropaleontological interpretation of the whole of Divisions A and B as bathyal deposits formed at depths of about 2000 ft (610 m) is unwarranted. The molluskan fauna present in the greater part of these units indicates they are predominantly littoral to outer neritic (0 to 800 ft (0 to 244 m)) deposits. Only the middle part of Division B could have been a bathyal (i.e. more than 800 ft (244 m) deep) deposit.A turbiditic redeposition of coarse clastics of Division A into the bathyal depth is ruled out by the state of preservation of its macrofossils, lithology of rocks, and the abundance of regular rows of early diagenetic concretions which maintain their stratigraphic position over considerable distances. The shales of Division B are not redeposited turbidites for the same reasons. If the abundance of allegedly bathyal foraminifers throughout the thickness of these two units will be confirmed by proper documentation and by further research it would be necessary to interpret their association with neritic macro-invertebrates as having been caused by the influence of strong upwelling currents which lowered the temperature of inshore waters and so made them habitable for these foraminifers.2. The recently proposed late Eocene dating of the upper part of Division A and the lower and middle parts of Division B cannot be justified either by the molluskan or by the foraminiferal fauna. The previously proposed early to mid-Oligocene age of these units remains valid regardless of whether one places them into the late Refugian foraminiferal stage or in the Lincoln molluskan stage.3. Even if it is valid, the unsupported claim of the presence of Bulimina schencki fauna does not indicate the correlation of these beds with the late Narizian, as this fauna is closely allied to and is probably contemporary with the early Refugian faunas of southern California. However, these beds may be of a latest Eocene age if the presence of Bulimina schencki fauna will be confirmed.4. The upper part of Division B contains an apparently Lower Blakeley macrofauna suggestive of late Oligocene age in terms of the generally accepted molluskan chronology. The early to mid-Zemorrian (=mid-Oligocene) dating of its foraminifer fauna reflects the divergent micropaleontological tradition which favors the placement of the Oligocene/Miocene boundary at the top of the Zemorrian stage.5. The suggested late Miocene to early Pliocene age of a shallow water foraminifer fauna of Division C of Nootka Island is contradicted by its stratigraphic position underneath the reliably dated Division D (see below). Only the upper part of Division C appears to be a neritic to ?littoral deposit. Its lower part is more likely an outermost neritic to uppermost bathyal deposit.6. The rich and diagnostic upper Blakeley (=lower Miocene) molluskan fauna of Division D is indubitably correlative with that of the type Sooke Formation of Southeastern Vancouver Island and with that of the "Sooke" Formation of the Seattle area. The early Miocene age of these three units is confirmed by the presence of a primitive whale tentatively referred to the order of Archaeoceti and the desmostylan genus Cornwallius in the type Sooke Formation. These data discredit the recently proposed early to early middle Pliocene dating of foraminifers of the Division D and the type Sooke Formation.7. No post-lower Miocene rocks are known to outcrop anywhere on the western coast of Vancouver Island contrary to the recent claims of some micropaleontologists. Also, there is no evidence of an unconformity separating the lower Miocene Division D from the underlying Oligocene to ?lowest Miocene Divisions A, B, and C. All four units appear to form part of a single invasion of a shelf-like (predominantly outer neritic to uppermost bathyal) Oligocene – early Miocene sea onto the southwestern part of Nootka Island. This sea, which may have been deeper and represented by a different facies elsewhere (i.e. Hesquiat Peninsula, Pachena–Sooke area), apparently withdrew completely and permanently from the west coast of Vancouver Island in the latest early Miocene.

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