Holocene climate change and sea level oscillations in the pacific coast of Mexico

摘要

A 2.75 m long core was recovered from La Joya lagoon at the southern Pacific coast of Mexico. The base of the core gave an age of ca. 5600 a BP. The AMS C-14 dating results indicate a continuously depositional history over the past 5600 years with varied sedimentation rates of 0.022-0.08 cm/yr. Sediment samples were analyzed for pollen, diatoms, loss on ignition (LOI), magnetic susceptibility and elemental analysis, to study the environmental and marine changes ocurred during the Holocene in the study site of the Pacific coast. Our data provided indications of the paleoenviromental changes in the study site from the south Pacific coast of Mexico: a complete marine environment from ca. 5600 to ca. 3200 a BP; a transitional lagoon from ca. 3200 to 1100 a BP; and followed by a shift toward a close lagoon with fresh water during the last 1100 years. The pollen data (the presence of pollen from Cucurbitaceae and secondary taxa related to disturbed vegetation) of La Joya record show evidence of agricultural activities and Human occupation in the study area might exist 5000 a BP.