Physical and acoustic properties of sediments off the coasts of Molokai and Lanai Islands, Hawaii

Abstract

Examination of physical and acoustic properties of carbonate-rich sediments was conducted on a suite of cores off of the coasts of Molokai and Lanai Islands, Hawaii. Carbonate mineralogy, grain size, grain density, porosity, bulk density and velocity measurements were systematically collected. In addition, bulk sediment []¹⁸O values were analyzed. Generally, there is a positive correlation between velocity, bulk density, percent sand, and high magnesium calcite and a negative relationship between velocity, percent clay, porosity, water content and low magnesium calcite. Down-core, bulk sediment []¹⁸O variability is a direct indicator of climate and sea level fluctuations. Glacial sediments, deposited during sea level lowstands, are isotopically heavy and characteristically have higher velocity, bulk density, sand and high magnesium calcite values, and lower measured clay content, porosity, water content and low magnesium calcite values than interglacial sediments. Property variability is influenced by regional differences in slope morphology, depositional controls, and water depth as well as physical, chemical, and biological processes and the properties of regional (intermediate) water masses. Identification of the glacial-interglacial transition and related physical and acoustic properties may be applied to high resolution seismic data interpretation and may enhance our understanding of the regional environmental conditions responsible for property formation.