Patterns of Tectonics, Provenance, and Sediment Fill in Large Complex Foreland Basins: Field, Petrographic and Detrital Zircon Analysis of Siliciclastic Turbidites in the Nanpanjiang Basin of South China

Reports: UR8 49341-UR8: Patterns of Tectonics, Provenance, and Sediment Fill in Large Complex Foreland Basins: Field, Petrographic and Detrital Zircon Analysis of Siliciclastic Turbidites in the Nanpanjiang Basin of South China

Daniel J. Lehrmann, University of Wisconsin (Oshkosh)

The goal of this projects is to use field characterization of the turbidite facies and paleocurrent indicators to determine the timing and fill directions of turbidite fan systems in the basin, to use petrography and detrital zircon analysis to evaluate potential source areas in the basin, and to evaluate the tectonic controls on the evolution of the turbidite systems and the impact of turbidite fill patterns on carbonate platform evolution.

Early office work on this project included extensive preparation for our first field season including the development of a detailed field plan and acquisition of key geologic maps, topographic maps, existing stratigraphic data and high resolution satellite images. Much of this preparatory work was done in connection with our colleagues in Guizhou. Field gear was assembled and special tools for measuring paleocurrent azimuths from sole markings were built. Thin sections from previously collected samples of turbidites from the basin, and from a previous provenance study in one area of the basin were investigated in order to become familiar with petrography ahead of the field season.

Field work was conducted for approximately 6 weeks in Dec. 09- Jan-10 and included measurement of several stratigraphic sections and reconnaissance of prospective sections to be measured in year 2. Field traverses took us across center and distal ends of the basin with sites chosen near potential source areas, in the middle of the basin and in intertonguing areas adjacent to platforms. Siliclastic turbidites were sampled in all areas for provenance and detrital zircon analysis. Interbedded carbonate facies were sampled for biostratigraphy to constrain age. Samples are currently being processed for laboratory analysis. Initial field results indicate two distinct source areas: a southerly convergent tectonic zone and a northeasterly uplifted Precambrian massif.

The project has had a significant impact in expanding the PI’s expertise into a new research area (provenance and sedimentology of turbidite systems) and in providing opportunities for two students to conduct laboratory study and another student to conduct field research in south China.