茂名盆地白垩系铜鼓岭组、始新统上垌组沉积特征OA

This study focuses on two field geological profiles of the Cretaceous Tongguling Formation and the Upper Eocene Shangdong Formation located on the northern side of the open pit mine ecological park in the Maoming Basin.Through a comprehensive analysis of lithology,rock composition,structural maturity,sedimentary structures,and sedimentary evolution,this research conducts a detailed division of sedimentary facies and explores the sedimentary environment,leading to the following conclusions.First,the Shangdong Formation represents a typical fan delta deposition.Vertically,the sedimentary sequence can be subdivided into two microfacies:braided distributary channels and marshes within the fan delta plain sub facies.Notably,an inverse stratification occurs at the top of the lower part of the profile,reflecting enhanced hydrodynamic conditions during fan delta accumulation.Second,the Tongguling Formation profile is predominantly characterized by beach sand deposition.From bottom to top,the alluvial fan phase's river microfacies,the lacustrine phase's marsh microfacies,and the beach sand microfacies can be identified.Among these,the horizontal bedding of the beach sand microfacies is well-developed,presenting as medium-to thick-bedded siltstone to fine sandstone with significant variations in sediment content between the upper and lower sections.Overall,the Tongguling Formation exhibits a normal grading sedimentary sequence that transitions from coarser grains at the base to finer grains at the top,with at least three interbedded cycles of beach sand and marsh deposits.This research enriches the understanding of sedimentary characteristics for the Cretaceous Tongguling Formation and the Upper Eocene Shangdong Formation in the Maoming Basin and provides valuable references for analogous reservoir studies.