Sedimentary facies,depositional processes and climatic controls in a Triassic Lake,Tanzhuang Formation,western Henan Province,China |
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| Authors: | María Gabriela Mángano Luis Alberto Buatois Xiantao Wu Junmin Sun Guocheng Zhang |
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| Institution: | (1) Facultad de Ciencias Naturales, Universidad Nacional de Tucumán, Casilla de correo I (CC), 4000 San Miguel de Tucumán, Argentina;(2) Jiaozuo Mining Institute, Jiaozuo City, Henan Province, P.R. China |
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| Abstract: | The Middle to Upper Triassic Tanzhuang Formation represents part of the infill of the early Mesozoic Jiyuan-Yima Basin. The upper part of this stratigraphic unit records deposition within prevailing shallow lake conditions. Well-developed sequences crop out near Jiyuan, western Henan Province, central China. Six sedimentary facies clustered into two facies assemblages were recognized in the lacustrine section. Facies assemblage 1 consists of stacked coarsening-upward sequences composed, from base to top, of organic-rich shales (facies E, type I), laminated siltstones (facies A) and current-rippled laminated sandstones (facies B). Units of assemblage 1 record progradation of small mouth-bar deltas within a perennial open lacustrine system under temperate and humid conditions. Facies assemblage 2 lacks a clear vertical pattern and consists of interbedded fine-grained carbonates and siltstones (facies C); deformed and wave-reworked sandstones (facies D); organic-rich shales (facies E, type II) and clayey mudstones (facies F). The assemblage also represents a perennial, hydrologically-open, shallow lacustrine system, but characterized by strong seasonal climatic control. Water stratification probably occurred in several periods of the lake history. Pangaean megamonsoonal influence is envisaged to explain the strong seasonality imprint evidenced toward the upper part of the Tanzhuang lacustrine column.This is the fourth paper in a series of papers published in this issue on  Climatic and Tectonic Rhythms in Lake Deposits . |
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