Permian Shanxi Formation and Member 8 of Xiashihezi Formationin Ordos Basin: Palaeogeography and catchment area for sediments derived from north and south provenances
Xiao JianxinSun Fenjin He Naixiang Liu Ruie Li Jing Xiao Hongping Zhang Chunlin
1 The Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, Ministry of Education,
China University of Geosciences(Beijing)，Beijing100083
2 College of Resources & Safety Engineering，China University of Mining & Technology(Beijing)，Beijing100083
3 Langfang Branch，Research Institute of Exploration and Development，PetroChina，Langfang065007，Hebei
Previous studies have not determined the location of the catchment area of the Shanxi Formation and Member 8 of Xiashihezi Formation sediments in the Ordos Basin derived from north and south provenaces. Thinsection analyses of sandstones from 4 outcrops and cores for 18 wells in the southern basin have been carried out in this study on the basis of understanding of the general data of the studied stratigraphic intervals in the Ordos Basin. The location of catchment area for the sediments of the Shanxi Formation and Member 8 of Xiashihezi Formation is defined in the southern Ordos Basin based on the changes of feldspar content and other lithological characters，the characteristics of log curves and rock assemblages，and the facies analyses of across well profiles and outcrops. The “catchment area” refers the area where the rivers transporting the sediments from north and south provenances merge and it is the bordering area which separates the
earlyderived sediments from the north to the south. It lies roughly in eastwest direction. There are obvious differences in feldspar content between the north and south sides of the catchment area. It is put forward that there are “intersection parts” of sediments from the north and south in local places of the catchment area. The “intersection parts” mean the areas where the sediments from the north and south meet and intersect with each other，which are the connecting places of the sediments from the north and south. The intersection parts are located in the catchment area and separate it into different parts. The siderite nodules formed in the early diagenetic stage under reduction conditions were found in the intersection parts of the Member 8 of Xiashihezi Formation. The palaeogeography of the southern basin during the deposition of the Shanxi Formation and Member 8 of Xiashihezi Formation was controlled by sediments from both the north and south. The acrosswell sections show that the sedimentary facies belts have a symmetrical distribution on the north and south sides of the catchment area. The sedimentary units and facies belts include:1)the catchment area，with three intersection parts; 2)the delta facies belt on the south margin of the catchment area，including 3 deltas from the south provenance; 3)the delta facies belt on the north margin of the catchment area，including 45deltas from the north provenance; 4)the fluvial facies belts which are the transitional belts of north and south deltas. The depositional model for the studied intervals in the study area in Ordos Basin is proposed.
About author:
Xiao Jianxin，born in 1958，is a professor and is mainly engaged in teaching and researches of sedimentology and sequence stratigraphy. Email:xiaojx@cugb.edu.cn.
Cite this article:
. Permian Shanxi Formation and Member 8 of Xiashihezi Formationin Ordos Basin: Palaeogeography and catchment area for sediments derived from north and south provenances[J]. JOURNAL OF PALAEOGEOGRAPHY, 2008, 10(4): 341-354.
. Permian Shanxi Formation and Member 8 of Xiashihezi Formationin Ordos Basin: Palaeogeography and catchment area for sediments derived from north and south provenances[J]. JOPC, 2008, 10(4): 341-354.
