Geomorphological aspects of the Jirau 01 fossiliferous natural tank, municipality of Itapipoca, Ceará state, Brazil

Abstract

The natural tanks (stricto sensu) are important geomorphological features that occur in the municipality of Itapipoca (CE), which occasionally accommodate Quaternary sediments with relevant fossil content. The ''Tanque Jirau 01'', located at the Jirau Paleontological Site, stands out among the various depressions that occur in this municipality of Ceará, both in terms of geomorphology and paleontology. The Jirau fossiliferous tank (TF01) is a steep natural tank, which was formed in the crystalline basement, presenting a concave-type bottom morphology. The depression follows the WNW-ESE orientation and is partially filled by sand-clayey sedimentary deposits, with fossiliferous content from the Pleistocene megafauna. Regarding dimensional aspects, the TF01 has an extension of more than 50 meters in length, with a maximum width of 5,30 meters and depths of up to 5 meters. The conformity of the geomorphological aspects, in addition to attributing to the TF01 an extraordinary scenic beauty, also made it possible to offer, in the past, an area of stock and availability of water for the fauna and, later, for the local population in periods of drought. Inside the tank, it is possible to verify the registration of minor structures on the lateral walls, features similar to honeycombs and/or alveoli with centimeter sizes, and evidence of weathering processes of soil-rock contact linked to chemical corrosion. Although there are paleontological studies in academia on the material found in the depressions of Itapipoca, there is still few materials linked to the conditions responsible for the possible origin and development of these natural tanks in the region. This study presents an initial analysis based on the morphological characterization and tectono-structural control of the Jirau 01 (TF01) natural tank, an area of important scientific reference in the municipality of Itapipoca (CE).