Nature of Margins of Sedimentary Basins: ABSTRACT

ABSTRACT Sedimentary basins, a subject of vital interest to economic geologists, differ to such a large degree that consideration of the origin of the variations is significant to economic geologists. The margin of the sedimentary basin, being the most variable part, merits special consideration. Several factors control the nature of a sedimentary basin and its geologic history. Primary among these factors are (1) the tectonic history, including the intensity of uplift of the adjacent source area and subsidence of the depositional site, (2) the physiography of the basin and adjacent source area, (3) the climate of the basin and adjacent source area, (4) the eustatic conditions of sea level during the basin’s history, and (5) the biological activity, faunal and floral, in the basin and adjacent source area. Secondary factors, controlled by the interplay of the primary factors, are (1) nature of terrigenous clastics produced in the source area, (2) rate of influx of terrigenous clastics into the basin, (3) energy relations in the depositional site related to transport and deposition of sediments, (4) stage of evolution of flora and fauna, and (5) the amount of time involved in the basin’s history. These factors, if evaluated in regard to basins of different ages and geographic locations, demonstrate why both modern and ancient basin margins are highly variable in regard to (1) thickness of sediment, (2) type and sequence of sediment, (3) facies relations of the sediment, and (4) tectonic history. In addition, this type of evaluation demonstrates the need for regional analysis as a framework for local analysis of any basin.