Dynamics of rocky shores; Cretaceous, Pliocene, Pleistocene, and Recent, Baja California Peninsula, Mexico

Rocky shorelines provide an excellent record that can be used to interpret the environmental conditions prevailing in a particular area in time and space. Former rocky shores are first-rate indicators of sea-level position, and they provide important local to regional information on tectonics and neotectonics. In this paper, sedimentary units made of gravel-size clasts, interpreted as having been deposited on a rocky shore, provide data for the interpretation of the hydrodynamic conditions under which the units were deposited. A model is presented by which to evaluate the minimum wave heights associated with rocky-shore deposits located on the Baja California peninsula, both on the Pacific and Gulf of California margins for Upper Cretaceous and Pliocene shoreface deposits and for a modern beach deposits. Elements considered under the application of the model are the average clast size and water depth assigned to each deposit based on an equation proposed by earlier workers in conjunction with Airy's linear theory. Results from the application of the model reflect the position of each deposit relative to sea level and the clast-size population for each deposit. Values calculated as minimum wave heights range from 3 m to more than 7 m. These are interpreted in the context of northern winter storms on the Pacific coast and tropical storms or hurricanes on the Gulf of California coast.