Geological observations and petrographic study on 54 samples collected by Dr. Laureano Rincón, in the department of Nariño in the Tambo, Peñol, Policarpa road
DOI:
https://doi.org/10.32685/0120-1425/bolgeol9.1-3.1961.133Keywords:
Colombia, petrographic classification, Cretaceous, deformative analysis
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Copyright (c) 1961 Servicio Geológico Colombiano
This work is licensed under a Creative Commons Attribution 4.0 International License.
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Abstract
To increase the data on the formations in the Patía basin, and based on a route survey, a series of samples were collected along the Tambo-Peñol-Policarpa route by engineer Laureano Rincón Orbegozo, of the Pasto Geological and Mining Service. Part of these was sent to this department for petrographic examination; another part was studied in the Paleontology department for the possible content of microfossils.
In 1930 Dr. Emil Grosse, who visited the region between Popayan and the mentioned route (El Tambo-Policarpa) for more than three months, made a detailed study and recorded his observations in volume III of the Compilación de Estudios Geológicos Oficiales en Colombia (Compilation of Official Geological Studies in Colombia), with the corresponding geological sketch. Dr. José Royo y Gómez made another study of Nariño and Alto Putumayo during four months in 1940; this study had especially an economic object, and its results are consigned in volume V of the same Compilation; throughout the present report, we shall frequently refer to these two authors.
The present study is mainly limited to the petrographic description of the samples. Because we do not know the region personally and the lack of precise data on extension, variation, geological position, and others, a geological interpretation would be very doubtful. Thus, for example, it seems that certain samples may correspond to a hyp abyssal formation and an extrusive formation. We have had to give the classification in these cases arbitrarily, according to the idea suggested by the sketch of the survey or the literature mentioned above. Other samples may come either from pebbles of a conglomerate, or from bombs of a volcanic agglomerate or lava.
Despite this, the material was treated by arranging it according to the geological formations of possible origin. In the last chapter, an effort has been made to deduce some geological observations. The appendix contains the study of all the samples according to the order of the survey.
