Structures and Their Tectonic Implications of the Southern Part of Cuddapah Basin, Andhra Pradesh, India

Abstract

Systematic structural observations in field outcrops can give clues to interpret orogenic events. Deformational structures studied in basement complexes as well as Cuddapah basinal sedimentary rocks indicate at least three events. The formation of N–S trending greenstone belts on gneissic basement complex is related to the oldest Kenoran orogeny. The later developed Hudsonian orogeny is related to opening of basin and numerous younger pluton as well as mafic dike emplacements. The Greenville or Eastern Ghats Orogeny is most intensively imprinted in the Cuddapah basin sedimentary rocks. The crescent shape of the Nallamalai fold belt in the east is due to the E–W compression related to thrusting followed by NNE–SSW compression. The E–W maximum compression (σ1) is related to the Eastern Ghats Orogeny, which is responsible for the development of several sympathetic E–W faults due to N–S extension (σ3). The formation of the Palaeo–Mesoproterozoic supercontinent Columbia is related to the E–W compression and the Napier Complex of east Antarctica connected with India occupying the indentation of the E part of the Cuddapah basin. Palaeostress study from the southern part of Cuddapah basin reveals that the initial E–W compression and associated fracturing produced E–W extensional regime, and subsequent NNE–SSW shear developed conjugate fracture set. However, the initial E–W compression was associated with the N–S extension component to develop broadly E–W parallel normal faults such as Vempalle fault and later strike-slip faults related to changes in the stress field. The proposed model explains the development and evolution of the Cuddapah basin as a new insight into the regional geodynamics.