Microfacies Study of Dissolution and Precipitation in Littoral Deposits on the Western Coast of Baja California Sur (Mexico)

Socorro Celts-Gutierrez, Victor M. Malpica-Cruz

Abstract


The study area, located on the western coast of Baja California, in its south-central portion, discloses several outcrops of well-preserved marine deposits at various elevations and thicknesses which are attributed to a series of Quaternary marine transgressions. The paleolittoral deposits form a belt parallel to the present coastline, and in some places there are as many as nine of these belts with heights between 5 and 90 m.The microfacies study provided an understanding of various diagenetic processes which have taken place in these deposits. The deposits consist mainly of weIl-consolidated sandstones and beach conglomerates, with both macrofauna and microfauna. The microfauna has been reworked and broken. These diagenetic processes took place in a mainly subaerial environment. The lithification began usually in a shallow marine environment and continued after the emergence under the influence of fresh water and variations of the water table, which led to the dissolution of the organic carbonates, mainly fossil shells. The oldest deposits show evidence of several dissolution phases and successive recrystallization of the cement, also the epigenesis of quartz and feldspar grains as well as caliche production as a result of Quaternary climactic changes.


Keywords


Beach conglomerate; macrofauna; microfacies; microfauna; marine terrace; paleolittoral deposits

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