Preliminary results of the depositional history of Kuwait Bay for the past millennium suggest a spatially and temporally variable mix of autochthonous and allochthonous sediment

The purpose of this study is to investigate the depositional history of Kuwait Bay (KB) for the past millennium based on sediment cores.  Kuwait Bay is in the northwest corner of the Arabian (Persian) Gulf, encompasses 720 km², is semi-enclosed, elliptically shaped, and is an inverse estuary that opens to the east. Kuwait is extremely arid, receiving rainfall typically ranging from 100-120 mm y^-1, and KB has no direct fluvial input within its interior.  However, KB does receive sediment from the Tigres-Euphrates River, which empties into the Gulf adjacent to the mouth of KB.   KB also receives sediment from dust storms and through direct precipitation of carbonates from the water column.  Although sedimentation rates and age dates have yet to be generated, if we assume as a rough estimation that sedimentation kept pace with average global sea level rise, which averaged approximately 2 mm y^-1 for the past millennium, then 2 m long cores roughly represent millennium time scales.  A total of 28 submersible vibracores, ranging in length from 1-2.5 m, were collected in 2021.  By using X-ray fluorescence (XRF) core scanning, elemental abundances were analyzed at 1 cm increments. Color spectrophotometry and grain size analysis were also conducted downcore. For all cores, the upper 10-25 cm have elemental abundances and colors that differ from the down core portions, and it is assumed this upper portion represents the Anthropocene.  When considering the pre-Anthropocene portions of the cores, the XRF elemental abundance ratio of Si/Ca was used to differentiate calcium carbonate from siliceous sediment.  The bay was subdivided into the eastern portion proximal to the mouth of the bay, the central portion, distal from either the mouth or the western shore, and the western portion, proximal to the western shoreline.  Although all Si/Ca abundance profiles are “spikey,” there are significant overall trends. Cores from the bay’s interior have overall lower Si/Ca ratios, indicating the cores have a greater abundance of calcium carbonate.  This may potentially indicate either higher auto-precipitation in the bay’s interior or less dilution of the auto-precipitated carbonate.  Cores around the interior western side of the bay have, overall, the highest Si/Ca ratios, suggesting a greater abundance of siliceous minerals.  Much of the dust derived from dust storms from this region is siliceous and probably explains this higher abundance of Si.  Si/Ca profiles from cores from near the mouth of the bay have the broadest range of ratios but overall have higher ratios than from the interior, potentially indicating a variability in advection of Tigres-Euphrates sediment into KB.  Overall, the depositional history suggests a mix of autochthonous sediment sourced from dust storms and the advection of Tigres-Euphrates suspended sediment and the auto-precipitation of allochthonous carbonates.  These are preliminary results of what will become a much larger investigation into the paleoclimate history of the region.