Quantitative paleogeographical reconstructions and basin evolution of South China during the Ordovician

High-resolution, quantitative paleogeographical reconstruction based on geological big data and Geographic Information System (GIS) is an important way to visualize regional and global paleogeographical features and their evolutionary processes, and to reveal the interaction of lithosphere, hydrosphere and biosphere. Ordovician sequences are widely exposed in South China with mostly continuous strata and abundant and diverse marine faunas. However, the lack of high-resolution, temporal-spatial paleogeographical maps of South China hinders a deep understanding of its paleogeographical pattern and dynamics. Based on the latest stratigraphical, paleontological and sedimentological results, the comprehensive data set from 807 Ordovician sections (or wells) in South China was collected and standardized under a unified chronostratigraphical framework. The lithofacies paleogeographical maps and stratigraphical thickness isopach maps of ten consecutive time intervals are quantitatively reconstructed with an average duration of ca. 4.1 Myr, and each map is supported by 300-666 sections for reconstruction. This study reveals precisely the timing and process of the major transformation of the land-sea distribution and basin basement in South China through the Ordovician at the biochron level. In the Jiangnan region, different paleogeographical processes are distinguished among the Guizhou-Guangxi, Jiuling, and Huaiyu terranes, which display distinct uplifting at different times with different consequences on strata, fossils, and environments in their surrounding areas. A new evolutionary process of the paleogeographical pattern of South China is recognized, which shows a great change from the platform-slope-shelf pattern in the early Early Ordovician to the platform-slope-basin pattern in the late Early to early Late Ordovician, and to the platform-depressions pattern in the late Late Ordovician. We also depict the distribution and migration of several depositional centers in South China, reveal the main provenance regions and assess their supply intensities of terrigenous clasts. The paleogeographical reconstructions demonstrate the associated evolution of the stabilization in the west and the intracontinental orogeny in the east of South China during the Ordovician and reveal the differentiated effects of regional tectonic movement and global sea-level changes.

Automated summary

High-resolution, quantitative paleogeographical reconstruction based on geological big data and GIS is crucial for visualizing regional and global paleogeographical features and their evolution, as well as understanding the interaction of lithosphere, hydrosphere, and biosphere. This study collected and standardized a comprehensive dataset of 807 Ordovician sections in South China, and reconstructed lithofacies paleogeographical maps and stratigraphical thickness isopach maps for ten consecutive time intervals. Precise timing and processes of land-sea distribution and basin basement transformation were revealed, showing distinct paleogeographical processes among different terranes. The study recognized a new evolutionary process of the paleogeographical pattern in South China and provided insights into depositional centers, provenance regions, and the effects of tectonic movement and sea-level changes.