Revisiting the latest Jurassic-earliest Cretaceous Los Santos Formation, Eastern Cordillera of Colombia. A – The history of its origin and the lowermost part of the unit

Abstract

A historical account is made of the way in which various researchers have conceptualized the regional geological framework and local exposure of a lithostratigraphic unit spanning from latest Jurassic to early Cretaceous, widely distributed in the Mesas and Cuestas region of the Eastern Cordillera of Colombia. In this first part of the revisit exercise of the Los Santos Formation, the lowermost part of the unit is analyzed, the development of its lithofacies from a detailed definition performed in the type section and its correlation with eleven additional stratigraphic sections. From this analysis, four main lithofacies with an important gravel-size quartz -quartzite content is determined east of the Suárez fault - south of the Los Montes transverse fault, while north of the area in the vicinity of the Lebrija and Solferino faults, the rudite fraction is almost entirely made up of brownish red sedimentary clasts. To the west of the Suarez fault-south of the Sogamoso fault, intercalated sandstones and shales predominate. A trend of sedimentological development is observed in all the stratigraphic columns with gravel-size contribution, from polymodal conglomerates, disordered fabric, poorly calibrated and supported by matrix to well-bedded intercalations of conglomerates, sandstones and shales. A structural control in the sedimentation is deduced, which is reflected in the shape, thickness and occurrence of the investigated facies and related faults.

Keywords

• Mesas and Cuestas; revisit; facies; tectonic response; Suarez fault