Advances and perspectives in the study of the genetic mechanism and organic matter enrichment models of marine fine-grained sediment

This study provides a comprehensive analysis of global advances in the study of the characteristics, origin, and organic matter enrichment model of marine fine-grained sediments. These sediments, mainly composed of clay minerals, quartz, carbonate minerals, and organic matter, are predominantly transported by four geological agents: wind, hypopycnal plumes, hyperpycnal plumes, and bottom currents. They exhibit clayey and silty laminae; single, sequential, and alternating laminasets; and massive, graded, and alternating beds. Covering three major types of sedimentary facies, namely turbidite, bottom current, and pelagic to semi-pelagic facies, as well as their transition types, the sediment demonstrates two organic matter enrichment models under high productivity and enhanced preservation. In the high productivity-derived model, the organic matter enrichment in black shales typically involves upwelling currents, oxygen-minimum zones (OMZ), and nearshore photic zone euxinia (PZE). In the enhanced preservation-related model, the enrichment principally involves restricted basins, improved restricted basins, irregular bed form, expanding puddles, transgressive chemocline, and transgressive nearshore (TN) zones. Current challenges in the research on the genetic mechanism and facies models of marine fine-grained sediments primarily include non-standard terminology, undefined origins of different mineral compositions, and the difficulty in distinguishing among three sedimentary facies: fine-grained turbidite, contourite, and semi-pelagic facies. Further research is required to address these issues.