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Holocene sea level changes in Kelang and Kuantan, Peninsular MalaysiaHassan, Kamaludin bin January 2001 (has links)
A proper methodological approach of investigating Holocene sea level changes is a prerequisite in order that the sea-level index points can be useful and significant. This requires the correct identification of the indicative meaning. The indicative meaning of the sea level indicator is defined as the altitudinal relationship of the local environment in which it accumulated to the contemporaneous reference tide level. This study identifies the index points using the litho-, bio-, and chrono-stratigraphic approach. The sea level indicator is derived from the regressive contact of the intercalated peat and marine clastic sequence, while the indicative meaning is estimated based upon the relationship with the contemporary samples. The study was carried out at two contrasting coastal locations, the fossil sites from Meru and Mardi in Kelang in the west and Penur (north and south transects) in Kuantan in the east, while the contemporary sites are from various ecological environments from both areas. Microfossil analysis of pollen and diatoms indicates that the former are more applicable, and defined the changing microfossil assemblages within the regressive contact of the sea level indicator samples. Seven sea level index points are identified. The finding agrees to the general assumptions of high mid-Holocene sea level history in peninsular Malaysia. A relative sea level difference between the west and east coast is indicated, but the significance, if any, is dealt with caution. The explanations of presumed differential crustal movement or sheer age/altitude variability of the index points are suggested.
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Paleogeography and sedimentology of the MacKenzie Basin, Northwest Territories, Canada: An evaluation of Devonian sea-level change, paleoecological controls on Paleozoic reef growth, and early diagenetic conditions.Corlett, Hilary 11 1900 (has links)
The MacKenzie Basin, located in the District of MacKenzie in the
southern part of the Northwest Territories, Canada, includes a thick succession of Middle Devonian strata. This basin, bordered to the east by the Canadian Shield and to the south by the Tathlina Uplift, was directly connected to the open ocean that lay to the northwest. Comprehensive facies analyses of the Chinchaga Formation, Lonely Bay Formation, Horn Plateau Formation, and Horn River Formation, which formed in this basin during the Early and Middle Devonian, shows that sedimentation was largely controlled by eustatic sea level changes. Accordingly, these strata reflect a long period of sea level rise during which shallow water evaporite deposition in the Eifelian was followed by open marine conditions that led to reef growth in the Givetian, and ultimately pelagic shale deposition in the Frasnian.
The Horn Plateau Formation is comprised of numerous isolated reefs
that are located along northeast-southwest direction over a distance of 350 km along the MacKenzie Basin ramp. Reefs in the southwest are dominated by
stromatoporoids whereas those in the northeast are dominated by corals. Although difficult to prove, it appears that the distribution of the stromatoporoids and corals may have been controlled by nutrients coming from coastal upwelling or runoff from the exposed Canadian Shield.
Effects of early diagenetic processes were evident on the MacKenzie
Basin ramp in an intensely bioturbated facies in the Lonely Bay Formation.
Burrows from this facies are dolomite-filled further down the ramp and calcite-filled proximal to the Canadian Shield in the east. Anoxic conditions and the
presence of sulphate reducing bacteria may have promoted early dolomite
formation in the burrows located in deeper water. Burrows further up the ramp were oxygenated and show evidence of input from the exposed Canadian Shield, both of which may have inhibited low-temperature dolomite formation.
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Paleogeography and sedimentology of the MacKenzie Basin, Northwest Territories, Canada: An evaluation of Devonian sea-level change, paleoecological controls on Paleozoic reef growth, and early diagenetic conditions.Corlett, Hilary Unknown Date
No description available.
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Sequence stratigraphy and facies analyses of the Dakota Formation, Jefferson County, Nebraska and Washington County, KansasKoch, Jesse 01 January 2007 (has links)
The estuarine to fluvial sediments of the mid-Cretaceous (Late Albian/Early Cenomanian) Dakota Formation of Jefferson Co., Nebraska (NE) and Washington Co., Kansas (KS) were deposited in a marginal marine setting along the eastern margin of the Cretaceous Western Interior Seaway.
Three depositional facies based on various lithic content are recognized in the study area: Facies 1: Fluvial Channel Facies, Facies 2: Paleosol/Interfluve Facies, and Facies 3: Bay Head Delta/Estuarine Facies. The facies interpretation helped confirm that the Dakota Formation was deposited in a marginal marine setting in which low-gradient fluvial systems supplied a wave-dominated, estuary system.
Petrographic analysis of the Fluvial Channel Facies concluded that the sandstones can be classified as quartz-rich lithic arkose. These findings differ slightly from previous studies on Cenomanian Dakota Formation strata in Thurston Co., NE.
Palynostratigraphic, subsurface, and sedimentologic evidence helped to delineate a more accurate sequence stratigraphic framework for the Dakota Formation in the study area. Three large-scale, unconformity-bounded, sequences (D0, D1, and D2) are recognized, within which deposits of the transgressive and falling stage systems tracts are preserved in the Dakota Formation in the study area. While no physical deposits exist for the falling stage and lowstand systems tracts, evidence for their past occurrence can be observed by the erosional nature of the sequence boundaries. Detailed analysis of the systems tracts framework allows delineation of a generalized sea-level curve for the Dakota Formation in the study area.
Analysis of the sequence stratigraphic framework revealed a Late Albian/Early Cenomanian sea-level fall that subsequently created valley incisions of over 25 m into the Late Albian D1 sequence. A careful literature review combined with sequence stratigraphic evidence suggests that a geologically fast-acting eustatic sea-level mechanism lowered worldwide sea-levels by more than 25 m from Late Albian into Early Cenomanian time. A reevaluation of the mid-Cretaceous "greenhouse" world suggests that a glacioeustatic component to the observed sea-level changes may have occurred. A Southern Hemispheric polar ice sheet with limited extent and volume compared to "icehouse" continental ice sheets, along with global alpine glaciers fed by wet climate cycles are hypothesized to account for sea-level fluctuations that resulted in valley incision and subsequent filling in the study area.
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The Mammalian Geochronology and Biogeography of Paşalar (Middle Miocene, Turkey)Bernor, Raymond L., Tobien, Heinz 01 January 1990 (has links)
The Paşalar fauna includes 56 mammalian species of European. Asian, African and North American origin. Evidence provided on the stage-of-evolution of the primates Sivapithecus darwini and cf. Kenyapithecus, the rodent Turkomys pasalarensis, insectivores, carnivores, rhinos, suids and ruminants suggests that Paşalar is correlative with the Late Langhian marine stage and European Mammal Neogene Zone 6., circa 15 Ma (million years ago). A review of the Paşalar fauna's biogeographic history suggests that it was aggregated by a succession of pulsed intercontinental geographic extensions tied to global sea-level lowering events during the earlier half of the Miocene.
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