Diagenetic environments of authigenic carbonates and opal-CT crystallization in lower Miocene to upper Oligocene deposits of the Norwegian Sea (ODP Site 643, Leg 104)

Abstract

Different generations of complex authigenic carbonates formed in siliceous muds (lithologic Unit IV) and hemipelagic clays (lithologic Unit V). The change in carbonate mineralogy reflects major compositional differences compared to sediments in Unit IV. Most prominent is an increase in altered ash as a primary sediment component and a sudden decrease of siliceous microfossils. Upward diffusion of cations, lowered salinities in pore waters, and elevated temperatures provide diagenetic environments favoring increased remobilization processes. -from Author