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Study of Reef and Depositional Environment of the Ordovician in the Southern Margin of Ordos.

Author: HaoSongLi
Tutor: LiWenHou
School: Northwestern University
Course: Mineral prospecting and exploration
Keywords: Ordos southern margin Ordovician Reef Depositional environment Geochemistry
CLC: P618.13
Type: Master's thesis
Year: 2011
Downloads: 156
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Abstract

In this paper, the southern margin of the Ordos Ordovician reefs in the study to fully absorb the results of previous studies based on field reconnaissance outcrop, collect relevant exploratory well data by geochemical methods of sample test analysis. System to study the distribution range of the reefs in the main reef, with a reef and rock type, clear the depositional environment of reef development, analysis of the the sedimentary microfacies its development and evolution of the reef, and carbon and oxygen isotopes, trace elements methods such as geochemical study of the reef, and analyzed on the basis of the the Ordos southern margin of the Late Ordovician Organic reef development of control factors and summed up the reefs in reef-forming model. Fuping from the southern margin of the Ordos reefs in mainly distributed in the Weihe River north of East to the West, the scope of Longxian about 250km, are the Late Ordovician Organic reefs to Fuping a small park - Jiangjunshan, Yaoxian peach song slope , the Chunhua Tiewa temple Jingyang Alex Hill, Yongshou good Zhi River and the Liquan dongzhuang reef profile field reconnaissance on the basis that the reef is composed mainly by corals, algae layer foraminifera; attached reef head cephalopods, brachiopods, gastropods, crinoids, trilobites, tooth-shaped stone, etc.; rock type is mainly composed of reef skeleton rock barrier sedimentary rocks, bonded rock within limestone, bio-broken limestone, algal limestone and dolomite. The reef sedimentary microfacies main divided base for the reef, the reef core, reef caprock, most of the reef core reef wing or the fore reef after reef difference, only in of Yongshou good Zhi River reef and liquan Dongzhuang reefs in divided reef wing microfacies. Reefs in many developmental evolution intermittent, discontinuous reef development has a multi-layer. The Late Ordovician Ordos southern edge of the main platform facies, platform margin reef platform margin slope facies, and deep-water ramp - Trough phase development of the open sea. The reefs in the study area that is being developed in the platform margin reef flat. Development of a large number of Late Ordovician Organic reefs, biological substantial absorption of light carbon isotope 12C heavy carbon isotope 13C enrichment in the water and makes the Late Ordovician carbonate rocks presented δ13C high value biological abundant reef facies carbonate δ13C value of the salt rock below the non-reef carbonate facies; the reef development seawater salinity and no significant change compared with the previous description of the main controlling factor for salinity is not reef development in this area; Late Ordovician δ18O value higher than the Early Ordovician, there is a certain degree of increased sea water temperature, warm water is more suitable for the survival of organisms, a certain role in promoting the development of the reefs in; closely related to high value biological role of strontium content late Ordovician study area, a large number of developing biological reef limestone strontium content was significantly higher. Ordos southern margin of the Late Ordovician Organic reef development mainly by tectonic conditions, paleoclimatic conditions, reef, basal conditions, syngenetic fault activity relative sea-level change, undersea terrain conditions, hydrodynamic conditions and water properties and other factors control, formed on the basis of their reef-forming model.

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