Controls on terrigenous sediment supply to the Arabian Sea during the late Quaternary: the Makran continental slope

• Published in: Marine geology Vol. 169; no. 3-4; pp. 351 - 371
• Main Authors: Prins, M.A, Postma, G, Weltje, G.J
• Format: Journal Article
• Language: English
• Published: 15.10.2000
• Subjects: Marine; ISW, Pakistan, Balochistan, Makran; ISW, Arabian Sea, Oman Gulf; ISW, Arabian Sea, Makran Accretionary Prism
• ISSN: 0025-3227
• DOI: 10.1016/S0025-3227(00)00087-6

The input of terrigenous sediment along the tectonically active Makran continental margin off south-western Pakistan (Gulf of Oman, northern Arabian Sea) is studied on the basis of sediment cores distributed along a transect from the upper slope to the abyssal plain. Spatial and temporal variations in sediment composition, sedimentation rate and turbidite frequency in late Pleistocene-Holocene time (last similar to 20 super(14)C ka) will be discussed and related to changes in sea level and climate, and tectonic activity.End-member modelling of the grain-size distributions of the hemipelagic and turbiditic sediments indicate that the sediments are adequately described as mixtures of three end-members, which represent turbidite sand, turbidite silt or eolian dust, and fluvial mud. The geochemical and mineralogical compositions of the hemipelagic sediments indicate that the eolian dust was dominantly supplied from the northern Arabian Peninsula and the Persian Gulf region, and that the fluvial input is from the Makran margin. The ratio of contributions of eolian and fluvial sediment in the hemipelagic intervals is used as an indicator of continental aridity, i.e. summer monsoon intensity.Highest Holocene turbidite frequencies and sedimentation rates are recorded at the deepest coring sites. They are related to the proximity of the deformation front of the accretionary prism. Turbidite sedimentation on the upper continental slope was most frequent during the last glacial period of sea-level lowstand, and continued during the entire deglaciation and sea-level rise. Infrequent turbidite sedimentation occurred during the Holocene highstand of sea level. Turbidite sedimentation during the period of late sea-level rise and the Holocene sea-level highstand is inferred to be due to the strong impact of episodic events (i.e. flash floods and earthquakes) and because of the narrow shelf of the active Makran continental margin.