Browsing by Autor "Juan Carlos Laya Pereira"

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Facies sedimentarias del pérmico en el flanco surandino de Venezuela
(Universidad Autónoma del Estado de México, 2007) Patxi Viscarret; Juan Carlos Laya Pereira
An upper Paleozoic sedimentation cycle has been found in the southern region of the Venezuela Andes, represented by rocks of Sabaneta and Palmarito Formations, located at the southeast of Maracaibo Lake, near to the Mucuchachi and Aricagua towns. Own to the lack of geological data needed to give, in a general way, proper interpretation of Paleozoic geological cycles. This work studies the associations of facies, in the section of Palmarito Formation located along to the El Palmar creek. This analysis is based on field and petrography existing data. The Permic of the studied area is a well defined sedimentical and stratigraphical unit. From the biostratigraphic analysis of faunal group it was possible to establish an age for the Permic (Cisuralian?-Guadalupian?) belonging to the Palmarito Formation, where it is common to find Mudstone, Packstone, wackestone, Rudstone and dolomites limestone’s-like rocks as well as fossil marine’s limolitas and shale whit a high degree of organic content. Furthermore, it was observed sandstones with a degree of almost 30% of porosity. Additionally, it is evident the stratigraphic discontinuities leading to the conclusion that these sequences can be related as continuous events of the same geographical basin. It is recommended to make a Total Organic Carbon analysis and a high resolution biostratigraphy of samples from the Permic age in this region.
Sedimentación del mioceno superior plioceno en el flanco norandino de los Andes centrales venezolanos
(2009) Omar Antonio Guerrero; D. Martín Jiménez; Juan Carlos Laya Pereira; M. L. Monsalve; Miguel José Alvarado Colmenares
A sedimentary model of Betijoque Formation (Upper Miocene – Pliocene) is proposed from the outcrops of Betijoque - Sabana de Mendoza zone. This research was carried out through fluvial facies analysis taking into account facies associations, architectural elements and geometric relationships. The interpretation allows to define their sedimentology meaning and their palaeogeography position within the proposed model. In the present study Betijoque Formation was divided into three units: Unit I (base), which has been characterized by bars and channels with lateral accretion, mainly sands and sometimes gravels. This Unit is interpreted as a meandering river formed mostly by sand. Unit II (middle) whose most important feature is an upwards coarsening of grains in the channels and bars. Accordingly, it has been interpreted as a meandering gravel river. And finally Unit III, which is represented as the top of the sequence and has been defined as fluvial and amalgamated colluvial deposits, which are adjusted to a braided deep gravel river system. In conclusion, the vertical sequence of Betijoque Formation is interpreted as a prograding alluvial fan system and the three units are located in middle and distal parts of the model.