Rafael López-Martínez

Calpionellid distribution and microfacies across the Jurassic/ Cretaceous boundary in western Cuba (Sierra de los Órganos)

Abstract A detailed bed-by-bed sampled stratigraphic section of the Guasasa Formation in the Rancho San Vicente area of the “Sierra de los Órganos”, western Cuba, provides well-supported evidence about facies and calpionellid distribution across the Jurassic/Cretaceous boundary. These new data allowed the definition of an updated and sound calpionellid biozonation scheme for the section. In this scheme, the drowning event of a carbonate platform displayed by the facies of the San Vicente Member, the lowermost unit of the section, is dated as Late Tithonian, Boneti Subzone. The Jurassic/Cretaceous boundary was recognized within the facies of the overlying El Americano Member on the basis of the acme of Calpionella alpina Lorenz. The boundary is placed nearly six meters above the contact between the San Vicente and the El Americano Members, in a facies linked to a sea-level drop. The recorded calpionellid bioevents should allow correlations of the Cuban biozonation scheme herein proposed, with other previously published schemes from distant areas of the Tethyan Domain.

Timing of speleogenesis of Las Karmidas Cave (Mexico): first description of pseudokarst developed in ignimbrite

*jpbernal@unam.mx Citation:

Morphological and mineralogical characterization of speleothems from the Chimalacatepec lava tube system, Central Mexico

*ralopezm@geologia.unam.mx Citation:

Pedosedimentary records of Holocene paleoenvironments in a dryland alluvial fan system in Sonora, NW-Mexico

In this work we present a detailed micromorphological analysis of a sequence of palaeosols and sedimentary units at La Playa archaeological site. This sequence is from the Late Pleistocene (Marine Isotopic Stage 2) to the Late Holocene. Complementing the micromorphological study, a geomorphological analysis is provided, in order to establish the origin of the landscape units. The results show that according to the geomorphology, La Playa constitutes an alluvial fan, formed by a complex, braided channel. The older unit, the San Rafael Palaeosol (SRP) is the most developed and has a set of features associated with the changing paleoenvironmental conditions such as weathering of the primary minerals, clay illuviation (evidencing humid conditions of the Terminal Pleistocene), pedogenic carbonate accumulation in the A horizon (related to dry environments of Altithermal). The SRP is buried by fluvial sediments, which include different facies interpreted as: floodplain, sandbars, and channels. These sedimentation events are associated with the end of the Altithermal period and evidence more active geomorphic processes, probably due to strong storms causing flooding and the migration of the main tributary. Above the sedimentary unit, the Boquillas Palaeosol (BOP), formed during the Late Holocene, is derived from fluvial-alluvial deposits causing a syn-sedimentary soil, with a more incipient development as indicated by micromorphological features.

Reply to the Comment of A. Pszczółkowski on "Calpionellid distribution and microfacies across the Jurassic/Cretaceous boundary in western Cuba (Sierra de los Órganos)" by López-Martínez et al. (2013)

1Instituto de Geologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Delegacion Coyoacan, C.P. 04510 Mexico D.F., Mexico; rafaelopez83@hotmail.com 2Comenius University, Faculty of Natural Sciences, Department of Geology and Paleontology, Mlynska dolina G, 842 15 Bratislava, Slovak Republic; rehakova@fns.uniba.sk 3Departamento de Geologia, Universidad de Pinar del Rio, Marti 270, Pinar del Rio, C.P. 20100, Cuba