Establishment of Upper Devonian Hongshanliang Formation and its geological significance in Baogutu stratigraphic minor-region, West Junggar tectonic belt
Establishment of Upper Devonian Hongshanliang Formation and its geological significance in Baogutu stratigraphic minor-region, West Junggar tectonic belt
A new set of red marine sedimentary assemblages (siliceous, silty siliceous, and tuffaceous siliceous rocks) has been discovered in the Hongshanliang section of the northern Baijiantan in the Baogutu stratigraphic minor-region, West Junggar tectonic belt. These sedimentary rocks have been dated to the late Devonian and are in conformable contact with the dark-gray to gray-black carbonaceous siltstones of the overlying Baogutu Formation. Through regional correlation studies, it has been confirmed that this set of strata exhibits significant differences from all the Upper Devonian in the study area and even the entire West Junggar stratigraphic area. This sedimentary sequence aligns with the "four principles" of "field recognition, interface distinction, regional correlation, and map expression." Therefore, a new lithostratigraphic unit known as the Hongshanliang Formation has been established. LA-ICP-MS zircon U-Pb dating of the Hongshanliang basalt, pillow basalt, and andesite yielded ages of 365.9±5.0 Ma, 370.6±7.4 Ma, and 374.6±3.6 Ma, respectively, indicating a Late Devonian age for these rocks. The confirmation of continuous deposition of the Hongshanliang and Baogutu Formations not only resolves any uncertainties regarding the age relationship between the Baogutu Formation and the Xibeikulasi Formation but also contributes to a more comprehensive stratigraphic sequence for the lower Carboniferous. Moreover, the discovery of Devonian sedimentary records in the Baogutu stratigraphic minor-region provides new data for the study of regional sedimentary and tectonic evolution in West Junggar tectonic belt.
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