Abstract

DUENAS JIMENEZ, Hernando  and  GOMEZ GONZALEZ, Clemencia. BIOSTRATIGRAPHY OF THE CANSONA FORMATION AT QUEBRADA PEÑITAS, SAN JACINTO BELT. PALEOGEOGRAPHIC IMPLICATIONS. Rev. acad. colomb. cienc. exact. fis. nat. [online]. 2013, vol.37, n.145, pp.527-539. ISSN 0370-3908.

In this paper the results obtained from the biostratigraphical analysis of 13 samples from the Cansona Formation are presented. These samples were collected along the Quebrada Peñitas. The Quebrada Peñitas cuts through the core of the Chalán anticline and it is located on the San Jacinto belt of the Caribbean region of Colombia. Based on the information obtained, it is possible to assign a Late Cretaceous age to the Casona Formation. For the lower part of the analyzed section, it is possible to assign a Late Campanian to Early Maastrichtian age. For the upper part, we assigned a Late Maastrichtian age. According to the micropaleontological content, all of the analyzed sediments were deposited on shallow marine near-coast environments, which received a great influx of terrigenous material. It is possible to observe a shallowing of the basin as we ascend stratigraphically. The microfauna collected includes only long-range Cretaceous benthonic foraminifera, which are indicative of marine environments but do not contribute much in assigning a more precise age. From the analysed samples of the upper part of the section, it was possible to obtain good assemblages of pollen and spores, including Buttinia andreevi, Zivisporites blanensis and Proxapertites humbertoides, among many others. These assemblages allow us to assign to this part of the section a Late Maastrichtian age, and assume that these sediments belong to the Proteacidites dehaani zone (Germeraad et al., 1968). Very good assemblages of dinoflagellates were recovered from samples collected on the lower part of the analysed section. They are characterized by the co-occurrence of species of the genera Andalusiella, Cerodinium and Senegalinium, which are indicative that these sediments belong to the Tropical Paleo-Belt (Malloy suite), as established by Lentin and Williams (1980). The palynological assemblages similar to those recovered from sediments belonging to Quebrada Peñitas have been widely reported throughout the Eastern Cordillera. During the late Cretaceous Period there was a shallow Tropical sea (Cansona Sea), in the San Jacinto belt region, that was interconnected with the seas that allowed the deposition of the sediments belonging to the Colon, Umir, and equivalent Units. In this paper is reported, for the first time, the presence of sediments belonging to the Proteacidites dehaani and to the Tropical Paleo-Belt located west of the current Romeral Fault.

Keywords : upper Cretaceous Dinoflagellates; Cansona Formation; Foraminifera; Paleoenvironment; Tropical Paleo-Belt.

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