Tectonically controlled sedimentation in marginal basins

Abstract

Recent sedimentary facies in marginal basins which are isolated from terrigenous sedimentation have been analysed in relation to their tectonic environment to generate a general evolutionary model for sedimentation in marginal basins of this type. Marginal basins are assumed to open symmetrically, while the sedimentation pattern is asymmetric. A volcaniclastic apron forms as a large submarine fan complex adjacent to the volcanic chain; beyond the distal end of the apron pelagic brown clay with a high content of montmorillonite, glass and phenocrysts accumulates. Pelagic oozes with high contents of CaCO 3 are deposited in distal parts of the basin. The volcaniclastic apron migrates toward the remnant arc, prograding over older pelagic sediments. Cessation of spreading has little effect on the sedimentation pattern if volcanism is still active. When volcanic activity ceases, the dominant sediment sources are biogenous and wind-blown pelagics. Most basins by this time have subsided below the carbonate compensation depth (CCD) and these brown clays accumulate at rates near 2.5 m/m.y. No simple pattern of sedimentation emerges from the available data in marginal basins adjacent to continents or to major sources of terrigenous material.