TITLE:
Sedimentary Petrology Characteristics and Their Implications for Provenance of Flowerpot Basin Jurassic System in Yanqing County, Beijing
AUTHORS:
Yaxuan Yuan, Hongliang Wang
KEYWORDS:
Tuchengzi Formation, Sandstone Components, Petrologic Characteristics, Provenance Analysis, Dickinson Triangular Diagram
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.6,
June
14,
2016
ABSTRACT: The
characteristics of sedimentary petrology are significant in determining
geological provenance. By using field outcrop observation and indoor
identification of thin sections, the characteristics of Jurassic system
Tuchengzi Formation clastic rocks exposed in the Beijing Yanqing “flowerpot”
basin, which include rock types, clastic composition and cement type, etc. have
been analyzed systematically to identify the provenance direction and tectonic
setting and nature of the provenance. Research shows that the sedimentary rocks
in this area belong to analluvial fan and braided river sedimentary rock system
and include mainly conglomerates, lithic sandstone, and feldspathic lithic
sandstone. The main compositions of the conglomerate are dolomite and limestone.
Nearly 50% to 70% of the sandstones are mainly polycrystalline quartz; 10% to
15% are feldspar; and 40% to 55% are composed of debris from mainly magmatic
and metamorphic rocks. A Dickinson triangular diagram indicates that the
provenance type in this area is recycled orogny evolving from clastic recycled orogeny
such as a collisional orogenic belt to a transitional recycled orogeny. On the
basis of the geographic position and tectonic setting, three types of
provenance can be identified in the Jurassic system Tuchengzi Formation. The
far source provenances are Archean erathem basement metamorphic rocks in the northern
basin and granite or adamellite that intruded rocks of the Late Jurassic epoch
of the Yanshanian period in the northeast. The nearby provenance is the
Mesoproterozoic erathem Changchengian system and Jixianianian system dolomite
in both the east and west.