Diatom records: marine laminated sequences

This article outlines the history of marine laminated sediment research and then focuses on the nature of diatom records from Quaternary laminated marine sediments. Laminated marine diatom ooze accumulates under conditions of varying supply of different sedimentary components such as diatom frustules and terrigenous grains, in areas where the bottom water dissolved oxygen concentrations are almost depleted and preclude bioturbation. This facilitates the preservation of the seasonal succession of surface water diatom blooms, as promoted by processes such as coastal upwelling and water column stratification and subsequent collapse. These seasonally laminated sediments, or marine varves, record information about oceanographic and climatic processes over subannual to millennial timescales, from locations such as semi-enclosed seas (e.g., Gulf of California, NW Mexico), silled basins (e.g., Santa Barbara Basin, California margin and Iceberg Alley, MacRobertson Shelf, Antarctica), and the open continental margin (e.g., Peru margin). Quaternary laminated diatom ooze also accumulates in the deep-sea in well-oxygenated waters but beneath convergent oceanic frontal systems, such as in the South Atlantic associated with the Polar Front Zone. Here, the presence or absence of the laminated diatom mat deposits reflects the movement of major oceanic frontal systems over glacial to interglacial timescales