Palaeogeomorphology and its control on the development of sequence stratigraphy and depositional systems of the Early Silurian in the Tarim Basin

Abstract

The Silurian in the Tarim Basin was deposited on the basement deformed by the Caledonian tectonic movements at the end of the Late Ordovician. The development and distribution of sedimentary sequences of the Early Silurian have been clearly controlled by the palaeogeomorphology of the Late Ordovician. Based on unconformity characteristics and distribution of erosion, several zones can be differentiated including a high uplifted erosion zone, a transitional slope zone and a depression zone. The central and west Tabei Uplift zones show high angular unconformity and intense erosion. The Tarim Basin in the late Ordovician shows characteristics of higher in the west, lower in the east while higher in the south, lower in the north. The Early Silurian mainly developed transgressive and highstand systems tracts on the whole, while the lowstand systems tract only developed partly below the slope break. The palaeogeomorphology controlled the clastic source supply and deposit distribution. Braided delta system and tidal flat-estuary system were deposited. The duration of uplifting of the Tazhong paleouplift was longer than that of the Tabei paleo-uplift, and deposition was later. This led to the lower and middle members of the Kepingtage Formation missing in that area. As a large-scale transgression occurred during the deposition period of the upper member of the Kepingtage Formation, sediment from the west of the basin was transported and deposited by tides and waves, forming tidal-marine debris systems above the uplift. Proximal alluvial fan and fan delta coarse clastic deposits developed in proximal uplift zone in the east and southeast of the basin, and braided delta put forward to the transitional zone between the edge of uplift and the sea. Large-scale tidal channel, sub-distributary channel and mouth bar of the delta front can form favorable reservoirs, and they are primary targets for oil and gas exploration. This research on sequence-depositional systems development and distribution controlled by palaeogeomorphology is significant in guiding the prediction of reservoir sandstones.

Distribution and erosion of the Paleozoic tectonic unconformities in the Tarim Basin, Northwest China: Significance for the evolution of paleo-uplifts and tectonic geography during deformation

“…The Lower Silurian is dominated by littoral and neritic terrigenous clastic facies (Liu et al, 2010); Zhang et al, 2008) The paleogeography is oriented from southeast to northwest, consistent with that of the paleo-uplift belts. From northwest to southeast, facies associations show a transition from fluvial delta and clastic shoreline deposits along the southern slope of the Tabei uplift, to neritic and shallow marine fine-grained clastics in the northern depression belt, and finally to clastic shoreline and delta deposits at the northern margin of the Southeastern paleo-uplift (Fig.…”

“…The gentle southeastern slope extended across the area of the Tangguzibasi depression to the southeastern basin margin with widespread stratigraphic onlap on unconformity T g5 . The eastern part of the northern depression received large-scale fluvial-delta deposits, which exhibited progradation from east to west or northwest (Liu et al, 2010). This is simply related to the collision and uplift of the Altyn block bounding the eastern basin margin, which formed an important sediment provenance region.…”

The Silurian red beds of Tarim Basin: Signals of palaeoenvironment, palaeoclimate, and sea‐level change

“…And according to J. Liu et al (2010), several unconformities within the Silurian strata were probably caused by local uplifts occurred within and around the basin, which accounted for falls in relative sea-level. In addition, Silurian delta systems occured in the north of the basin, such as the Keping area, the Yingmaili area, the Hade area, and the Caohu area which suggested a strong fluvial action caused by the basin-margin exposure.…”

“…The Silurian marine clastic succession of the Tarim Basin succeeds the Cambrian–Ordovician marine carbonate deposits and contains important oil and gas reservoirs. It was formed during subsidence and sea‐level rise across the Tarim Basin in a period after the large‐scale uplift caused by the Caledonian tectonic movement of the Late Ordovician (C. Z. Jia, ; C. Lin et al, ; C. S. Lin et al, ; J. Liu et al, ; Mu et al, ) and shows a widespread unconformity on top of the basin (C. Lin et al, ; Wu et al, ). The tectonic upheavals of the Late Ordovician impacted many basins globally.…”

Three depositional models interpreting the Late Ordovician deep‐water gravity flow systems in the Tarim Basin, Western China

“…Many studies have shown that paleo-geomorphology has a very strong influence on the development of reservoir depositional systems (Lin, et al, 2009;Liu, et al, 2010;Posamentier & Kolla, 2003). Through the restoration of the erosion thickness caused Ordovician (Jia, Li, Zhang, & Li, 2007;Lin, et al, 2011;.…”