The study area includes the western part of the Tethys Sea, which was a zonally oriented tropical sea at a paleolatitude of about 0°-25°N and isolated from the Panthalassa Ocean by an isthmus. The sea was characterized by warm tropical surface water and generally strong net evaporation creating conditions of low oxygen content and elevated salinities in the surface water mass. Much of the margin receives insufficient precipitation to maintain lasting soil moisture or generate runoff to the sea in any season, precluding development of a lush vegetative cover. The general lack of runoff improves conditions for reef growth and carbonate deposition on the continental shelves. Much of the margin possesses wind-driven coastal upwelling. As a positive correlation exists between upwelling and high primary productivity on the margins of today's World Ocean, we predict that a similar relationship occurred in the Kimmeridgian Western Tethys Sea.