Deltaic sedimentation in the Devonian of Western Libya
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Transgressive
Devonian
Sedimentation
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Devonian
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The Devonian System in the Dianqiangui Basin and its adjacent areas consisting of three parts. The lower part is a set of transgressive sandstones, the middle is a mixed rock series and the upper is marked by a set of carbonate rocks. For the Devonian System of the Dianqiangui Basin and its adjacent areas, 13 third-order sedimentary sequences can be discerned and they can be grouped into two second-order tectonic sequences. In different depositional periods, the facies-succession features of the third-order sequences and their regular spatial changes reflect various palaeogeographical patterns. Controlled both by the global sea-level changes and by the regional tectonic movements, a particular Devonian filling succession of the sedimentary basin was formed. The third-order sea-level changes in the study area differ greatly from those of Europe and America.
Devonian
Sequence (biology)
Transgressive
Late Devonian extinction
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Abstract The Caledonian orogeny at the end of the Silurian resulted in great changes in the palaeogeography in the Yunnan-Guizhou-Guangxi area of South China; the continental area of the Early Paleozoic evolved into the extensive Dian-Qian-Gui Sea in the Late Paleozoic. Early in the Devonian, as a result of a major transgression, seawater encroached gradually from the south to the north and clastic facies were deposited. Carbonate deposition was then established in the Yunnan-Guizhou-Guangxi area, with a palaeogeography marked by attached platforms, isolated platforms and narrow basins. As a result of the Ziyun movement towards the end of the Devonian, the Upper Devonian strata are regressive and thin out from the open-sea to the land areas. A study of the nature and distribution of sedimentary facies in space and time recognises 13 third-order sequences in the Devonian strata in Yunnan-Guizhou-Guangxi area, and these form two second-order sequences. The strata of the Lower Devonian comprise 5 third-order sequences (SQ 1 to SQ 5 ), which are dominated by transgressive clastics. 4 third-order sequences (SQ 6 to SQ 9 ) in the Middle Devonian are characterized by alternations of transgressive clastics and highstand carbonates. In the Upper Devonian, carbonates constitute 4 third-order sequences (SQ 10 to SQ 13 ), which are generally marked by the transgressive limestones and highstand dolomites. On the basis of earlier biostratigraphic studies, sea-level changes represented by the third-order sequences with their different facies successions are explored, and the sequence stratigraphic framework is established. Therefore, the Devonian strata in the study area provide an example for further understanding of depositional trends within the sequence-stratigraphic framework.
Devonian
Transgressive
Marine transgression
Palaeogeography
Late Devonian extinction
Orogeny
Carbonate platform
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ABSTRACT Published geological information indicates that the Devonian rock succession onlaps a pre-Devonian paleotopographic high region located in west-central Alberta, named the Peace River Arch. The more elevated parts of this arch were emergent during the Devonian and acted as a source for detritus. A succession of coarse grained continental and nearshore, arkosic sandstones overlies and surrounds the arch. An interbedded succession of Upper Devonian carbonates and shales onlaps the sandy facies, and fringes and overlies the arch. Many of the Devonian units surrounding the arch thin to zero or change facies over the arch, so that it is difficult to sketch a depositional history based on a sedimentary and stratigraphic analysis of the onlapping beds. The depositional onlap pattern of the oldest beds indicates that the carbonates and shales of the Beaverhill Lake Group are in lateral facies contact with the nearshore, sandy Granite Wash facies that fringes the arch. The Woodbend Group overlies the Beaverhill Lake Group and includes an older reefal mound facies (the Leduc Formation), a dark inter-mound shale facies (including the Majeau Lake and Duvernay formations) and a younger, greenish grey shale facies that overlies the dark shale facies and abutts and overlies the carbonate mounds (the Ireton and Fort Simpson formations). Available information suggests that the Winterburn equivalents that overlie the Leduc fringing reef facies also overlie most of the area underlain by the arch, and onlap the Granite Wash facies in the higher parts of the arch. The peloidal and argillaceous limestones of the Wabamun Group overlie the carbonates of the Winterburn Group. Several map units of the Wabamun can be traced across the arch as being in facies contact with the Granite Wash sandstone. The Wabamun is locally absent in the crestal region of the Peace River Arch. The uppermost Devonian rocks in west-central Alberta belong to the Exshaw Formation. They comprise a relatively thin unit of dark grey, radioactive shale that includes a bentonite layer. It can be demonstrated that the Exshaw and the uppermost unit of the Wabamun Group are locally absent over the arch, presumably because of non-deposition. By removing the regional dip to the southwest and the compactional curvature across Peace River Arch, one can calculate second order residuals and draw a contour map based on the plotted values. This contour map outlines the fault-controlled depressions that are locally present in the axial region of the Peace River Arch. The depressions are filled with rocks of Mississippian age and attest to a later period of crustal extension. End_of_Record - Last_Page 173-------
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Conodont biostratigraphy is investigated in the Poyuan, Shangkou, and Menggong sections in Guangxi, and the Lower Emsian (Lower Devonian) excavatus and nothoperbonus zones are partly recognized. Combining the Lower Devonian conodont framework and lithological successions to date, the process of the Early Devonian northeastward stepwise transgression in South China is more elaborated in detail herein. It is proved that the differentiation of the “Xiangzhou Facies” and the “Nandan Facies” in South China took place in the nothoperbonus Zone. A series of high‐resolution Early Devonian palaeogeographic maps of South China is illustrated in this study.
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Conodont
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Jurassic is the main source rocks of Qaidam Basin,distributed mainly in the northern margin of the basin.Based on the comprehensive studies of marker beds,lithological features and sedimentary characteristics,the alluvial fan facies,braided river facies,fan delta facies,braided river delta facies and lacustrine facies are distinguished in Jurassic deposits in the main sections exposed.Both the facies belt distribution and paleogeographic evolution are closely related to the regional tectonic movement.There are two evolution stages that include the faulted lake basin sedimentary stage from Early to Middle Jurassic and the depression lake basin sedimentary stage during Late Jurassic,according to the stratigraphic contact relations and sedimentary evolution.
Alluvial fan
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The Emsian sediments of the Holy Cross (Świety Krzyz) Mountains in Central Poland include an essentially marine seque nce (Łysogory facies) and a continental placoderm series (Kielce facies). Placoderm facies occur within the marine sequence. A new richly fossiliferous deposit from the continental sequence has yielded abundant remains of acanthodians, arthrodires, the crossopterygian Porolepis, and heterostracans in particular psammosteids. These Emsian psammosteids show similarities to the Middle Devonian Baltic forms. They appear more likely to be the forerunners of the Middle Devonian Baltic forms than does the Siegenian and Emsian Drepanaspis which is a marine-lagoonal type.
Devonian
Sequence (biology)
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The Caledonian orogeny at the end of the Silurian resulted in great changes in the palaeogeography in the Yunnan-Guizhou-Guangxi area of South China; the continental area of the Early Paleozoic evolved into the extensive Dian-Qian-Gui Sea in the Late Paleo-zoic. Early in the Devonian, as a result of a major transgression, seawater encroached gradually from the south to the north and clastic facies were deposited. Carbonate deposition was then established in the Yunnan-Guizhou-Guangxi area, with a palaeogeography marked by attached platforms, isolated platforms and narrow basins. As a result of the Ziyun movement towards the end of the Devonian, the Upper Devonian strata are regressive and thin out from the open-sea to the land areas. A study of the nature and distribution of sedimentary facies in space and time recognises 13 third-order sequences in the Devonian strata in Yunnan-Guizhou-Guangxi area, and these form two second-order sequences. The strata of the Lower Devonian comprise 5 third-order sequences (SQ1 to SQ5 ), which are dominated by transgressive clastics. 4 third-order sequences (SQ6 to SQ9 ) in the Middle Devonian are characterized by alternations of transgressive clastics and highstand carbonates. In the Upper Devonian, carbonates constitute 4 third-order sequences (SQ10 to SQ13 ), which are generally marked by the transgressive limestones and highstand dolomites. On the basis of earlier biostratigraphic studies, sea-level changes represented by the third-order sequences with their different facies successions are explored, and the sequence stratigraphic framework is established. There-fore, the Devonian strata in the study area provide an example for further understanding of depositional trends within the sequence-stratigraphic framework.
Devonian
Transgressive
Marine transgression
Palaeogeography
Late Devonian extinction
Orogeny
Sequence (biology)
Carbonate platform
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Palaeogeography
Siliciclastic
Marine transgression
Marl
Sequence (biology)
Shoal
Sequence Stratigraphy
Transgressive
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Citations (59)