基于定量古地理的BQART模型深时古地势重建方法——以晚二叠世峨眉山大火成岩省内带为例

Using BQART Model to Reconstruct Paleo-relief in Deep Time Based on Quantitative Paleogeography:A case study from the Late Permian central Emeishan Large Igneous Province

源—汇系统分析下的古地势重建是当前沉积学领域的一个热点方向。古地势重建对于理解区域构造演化、气候变化、地表风化、物源供给及其相互关系具有重要作用。BQART沉积通量模型提供了入海流域中沉积通量与地质背景B、水流量Q、流域面积A、最大地势高度R、年均温度T之间的经验关系,逐渐发展为深时尺度下古流域地势重建的重要工具。本文在综合层序—古地理、旋回地层学、古水文比例关系和古地貌比例关系等方法的基础上,提出基于定量古地理的BQART模型深时古地势重建方法,结合沉积体积回填法可进一步获得构造抬升幅度与速率。通过该方法获得峨眉山大火成岩省内带古地势在晚二叠世期间持续缓慢上升,至晚二叠世末达200余米,累计构造抬升幅度约500~750 m。该深时古地势方法适用于气候温暖湿润、构造相对稳定条件下的中大型外流盆地,对能源盆地的勘探开发具有重要意义。

Paleo-relief reconstruction in source-to-sink system analysis is currently a hot topic in sedimentology,playing an important role in understanding regional tectonic evolution,climate change,surface weathering,sediment supply,and their interrelationships,and it is a key component of source paleogeographic reconstruction.Source ar⁃eas in deep time are not well preserved due to later tectonic destruction,weathering,and denudation,making it diffi⁃cult to reconstruct paleo-relief.The BQART sediment flux model depicts the relationship between sediment flux,bed⁃rock lithology,river discharge,drainage area,maximum relief,and annual average temperature in an exorheic set⁃ting.When sediment flux and other parameters are acquired from the sedimentary record,maximum relief can be cal⁃culated using the BQART model.Through integration of lithofacies paleogeography,cyclostratigraphy,paleohydrolog⁃ical and paleogeomorphological relationship methods,a BQART model-based approach is proposed for paleo-relief re⁃construction in deep time and,based on quantitative paleogeographic reconstructions,and uplift amplitudes and rates can be calculated by employing the sediment-volume backfilling method.Based on this approach,the inner zone of the Emeishan Large Igneous Province(ELIP)was estimated to be rising slowly during the Late Permian,reaching more than 200 m at the end of the Permian,with total tectonic uplift estimated as 500⁃750 m.This comprehensive analysis demonstrates that deep-time paleo-relief reconstruction approaches are suitable for a middle-large exorheic basin with a warm and humid paleoclimate,which is of great significance for the exploration and development of min⁃eral resources in energy-rich basins.