2:45 PM - 3:00 PM
[BPT23-16] Lithostratigraphy of mesoproterozoic stratum at Jixian, north China
Jixian area, North China, is one of the best places to decode surface environments during the Mesoproterozoic, because Mesoproterozoic-Neoproterozoic rocks well crop out there. Shallow marine clastic rocks and carbonates were successively deposited on Archean basement rocks. Age constraints for the succession in the Jixian are insufficient, therefore the purpose of current study is to constrain depositional ages of the sediments, basement gneiss and intrusive granite.
We conducted geological survey at the Jixian and collected these rocks. Sedimentary structures, including stromatolite, cross bedding, ripple, stylorite, storm rock, unconformity and basal conglomerate, indicate that sedimentary environment was shallow, above wave base, throughout the sections. Basement rocks in this area are composed of orthogneiss and hornblende-plagioclase gneiss. The mineral assemblage of the former is Qz-Bt-Grt, and that of the latter is Qz-Hbl-Pl-Grt-Chl. Main constituent minerals in intrusive granite are quartz, feldspar, hornblende and biotite, and its K-feldspar-rich mineral assemblage might imply A-type granite. Rock descriptions and lithostratigraphy of the Jixian area will be introduced in this presentation.