关键词: 大别造山带, 初始剥露, 宁芜盆地, 黄马青组, 物源分析

Abstract: Due to post-orogenic multi-stage tectonic events and long-term massive denudation, there are poor precise constraints to limit the initial denudation time of the Dabie orogen, that is, timing of starting to provide a source for the peripheral basins. In this work, we conduct field investigations on the Huangmaqing Formation, a set of Middle Triassic delta facies terrigenous clastic rock in Ningwu Basin, northeastern South China, and presents sedimentologic and provenance analysis. Lithologies of the Huangmaqing Formation are dominated by the litho-quartzose sandstone and feldspathic-litho-quartzose sandstone, with quartz of 76%-84%, lithic fragment of 10%-14%, and feldspar of 6%-11%. Among the lithic fragments, quartz-rich metamorphic rock fragments or metapelite grains rock debris are dominant, indicating the existence of special sources of metamorphic rocks. The detrital zircon age spectrum shows the main peaks at 350-250 Ma、420-400 Ma、900-700 Ma、2000-1600 Ma、2500-2100 Ma. The Susong Complex belt located in the southern orogenic belt is the main source of the Huangmaqing Formation. Compared with the sedimentary records of other early Mesozoic basins around the Dabie orogen, it is found that these basins have similar provenance in the Middle-Late Triassic. The early exhumation of the lower metamorphic belts in the Dabie orogenic belt led to the initial denudation of the orogenic belt. At least part of the sediments of the Huangmaqing Formation were derived from the early uplift and denudation of the orogenic belt.

Key words: Dabie Orogen, initial denudation, Ningwu basin, Huangmaqing formation, provenance