西南石油大学学报(自然科学版) ›› 2008, Vol. 30 ›› Issue (1): 33-37.DOI: 10.3863/j.issn.1000-2634.2008.01.010

• 地质勘探 • Previous Articles     Next Articles

Sequence Lithofacies Paleogeography of Western Ordos Basin in Majiagou Stage,Ordovician

YAO Jing-li 1,2 ZHAO Yong-gang3 LEI Bian-jun4 HAO Hai-yan2   

  1. 1.Chengdu University of Technology,Chengdu Sichuan 610059,China;2.Research Institute of Petroleum Exploration and Development,Changqing Oil Field Company,PetroChina,Xi'an Shanxi 710021,China;3.Xi'an Petroleum University,Xi'an Shanxi 710065,China;4.Southwest Petroleum University,Chengdu Sichuan 610500,China
  • Received:2007-03-06 Revised:1900-01-01 Online:2008-02-20 Published:2008-02-20
  • Contact: YAO Jing-li

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Abstract: Lower Ordovician strata in western Ordos Basin are mainly composed of huge-thick marine carbonate and evaporite,and can be divided into 12 third order sequences,the Majiagou Formation,one of them,includes 8 third order sequences.These sequences mostly belong to TypeⅡsequence and are mainly consisted of shelf margin system tract（SMST）,intra-shelf lowstand system tract（ISLST）,transgressive system tract（TST）and highstand system tract（HST）.Mainly taking Osq7,Osq8,and Osq9 sequences in Majiagou Formation of Lower Ordovician as examples,system tract as mapping unit,sequence lithofacies paleogeographic maps of the early Ordovician Majiagou stage are mapped by adopting system tract compression method in western Ordos Basin.Characteristics and evolution of lithofacies paleogeography of the early Ordovician Majiagou stage are studied in western Ordos Basin.The SMST-ISLST are featured by the Central Paleouplift Zone becoming subaerial exposure and larger-scale paleo-land.The TST are characterized by the development of carbonate platform facies and the appearance of carbonate shelf,slope,and trench facies.The HST is typically featured by the enlarging of dolomite flat,accretion of carbonate platform and appearance of intra-platform shoals.Under the control of sea-level fluctuation and ancient tectonic framework which was consisted of the Central Paleouplift,Helangshan aulacogen,and others,the lithofacies paleogeographic framework of the early Ordovician Majiagou stage totally shows that successive distribution of trench,slope,shelf,platform/paleo-land,intra-shelf basin margin facies are orderly oriented in the direction from west to east in western Ordos Basin.

Key words: sequence stratigraphy, system tract, lithofacies paleogeography, Majiagou Formation, Lower Ordovician, western Ordos Basin

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