Stratigraphy and palaeodepositional environment of the Palaeoproterozoic volcano-sedimentary Konse Group in Tanzania
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Keywords:
Conglomerate
Pillow lava
Lithology
Paleocurrent
The paleoflow direction of the basal conglomerate of the Changzhougou formation is obtained by the paleocurrent analysis of certain sedimentary structures, and the ancient sedimentary environment of the Qian’an Region is determined by observing the psephicity and gradation of gravel in conglomerate. The results show that the paleoflow direction is from northwest to southwest, and the paleocurrent data manifest a single-peak style in a rose diagram. The average paleoflow direction in the Qian’an region is 265°. The basal conglomerate is of littoral facies, and the sediments of conglomerates are mainly sourced from Shanhaiguan.
Paleocurrent
Conglomerate
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Abstract Quartzite cobble and boulder conglomerates are widely scattered through the Paleocene-early Eocene stratigraphic record of the western Bighorn Basin, Wyoming. Paleocurrent indicators, in conjunction with the timing of tectonic events in northwest Wyoming, demonstrate that accumulation of these conglomerates was instigated by episodic orogenic activity in the Jackson Hole area, over 100 km west of the Bighorn Basin. Deformation resulting from intrabasinal tectonic pulses also controlled the periodicity of gravel influxes to the Bighorn Basin as well as the depositional settings in which the quartzite conglomerates formed. Different modes of deposition are distinguished on the basis of conglomerate outcrop pattern and distinctive suites of depositional facies. The oldest (earliest Paleocene) conglomerate is dominated by massive or horizontally bedded cobble conglomerate that was deposited by a braided river that flowed through an area of dissected, upturned strata along the western margin of the Bighorn Basin. Unusually thick sets of planar cross-stratified conglomerate are also common and are attributed to deep and prolonged floodstages, reflecting humid conditions and valley confinement of the stream system. In contrast, the youngest (early Eocene) conglomerate, though dominated by massive or horizontally bedded conglomerate, lacks abundant large scale cross-bedded conglomerate and was deposited on an extensive braidplain. Facies change markedly over short distances due to lateral spread of flow on the braidplain and decrease in paleoslope toward the Tertiary structural axis of the Bighorn Basin.
Conglomerate
Cobble
Paleocurrent
Outcrop
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Paleocurrent
Conglomerate
Devonian
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Tectogenic sediments of the latest Cretaceous-Paleocene Evanston Formation were deposited in proximal braided streams in northeastern Utah, and in distal gravelly rivers in the Fossil basin of southwestern Wyoming. Paleocurrent data provide evidence for a north-to-south axial drainage system in both areas. The ubiquitous presence of Precambrian-Cambrian clast types throughout the Evanston Formation indicates a source area in the present day Bear River Range (Paris and Willard thrust plates). The Sublette Range Conglomerate is a crudely stratified, clast-supported, proximal braided stream deposit. Paleocurrent data and clast lithology also indicate a north-westerly source area on the Paris and Willard plates. It is proposed that the undated Sublette Range Conglomerate is a remnant of a proximal deposit which linked distal Evanston sediments in the Fossil basin with their source area on the Paris and Willard plates. Early Eocene reactivation of the Crawford thrust resulted in the present elevated position of the Sublette Range Conglomerate.
Paleocurrent
Conglomerate
Lithology
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Conglomerate
Paleocurrent
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In the alluvial part of the Promina beds of northern Dalmatia (Late Eocene to possible Early Oligocene age) the main, SW-ward paleocurrent pattern was determined from clast orientation measurements within massive and flat-bedded conglomerates. Preferred clast fabric, facies characteristics, and downward transition into shoreline and shallow-marine sandstone and conglomerate suggest a prograding, braid delta system.
Paleocurrent
Conglomerate
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A coarse conglomerate, known as "the Gravel of Reno," fills a deep channel incised into a 2.6 Ma sedimentary section a few km west of Reno, Nevada. The canyon and its conglomerate fill record an abrupt shift in both provenance and paleocurrent direction compared with the underlying lake-marginal Neogene strata. Notably, the intermediate volcanic provenance of the Neogene section is supplemented in the overlying conglomerate by large plutonic clasts derived from the Sierran batholith. The syntectonic Gravel of Reno signals the initiation of Pleistocene faulting along the eastern edge of the Sierra Nevada near latitude 40° N.
Conglomerate
Paleocurrent
Neogene
Batholith
Early Pleistocene
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