Mesozoic global environments

Old oceans have disappeared and new oceans have been created repeatedly in Earth history. Associatedchanges in continental distribution, oceanic circulation, and episodic magmatism (large igneous provinces)have been implicated in altering paleoclimate, paleoceanography, and sea level, as well as in forcingbiological changes. In Cretaceous time, the two major oceans—Tethys and the Pacific—differed enormously.Prior to Aptian time, Tethys was characterized by massive carbonate deposition, whereas radiolarian claysdominated the Pacific. In mid-Cretaceous time, Tethyan waters contained little oxygen, as recorded by blackshales, whereas deep Pacific waters were well oxygenated. We seek to understand why these oceans differedin Mesozoic time, as well as more generally to determine the climatic process(es) that operated in Cretaceoustime, the mechanism(s) that sustained the extremely warm Greenhouse Earth, and the process or event thatterminated the Greenhouse climatic pattern (eg, cessation of global circum-equatorial circulation). Specificgoals in studying the Mesozoic sedimentary record in the ocean are to investigate: the dominantMilankovitch frequencies during the Greenhouse; the operation of and variation in biogeochemical cycles;the effects of evolution, radiations, and extinctions on carbonate cycling; the variation in locus of carbonatecycling and budgets between continental shelves and the open ocean; the variation of the carbonatecompensation depth (CCD); the balance between oceanic and continental chemical fluxes; and the history ofand processes affecting oxygenation, in particular oceanic anoxic events (OAEs). Drilling is the only meansof obtaining the detailed Mesozoic sedimentary sections necessary to understand Mesozoic globalenvironments, and environmental changes and their causes. Optimal site selection for attaining the scientificobjectives of drilling Mesozoic sedimentary sections will require extensive regional 2D and local 3Dmultichannel and wide-angle seismic control of a quality and scale currently typical only in areas ofintensive hydrocarbon exploration.