Middle Eocene deformation and sedimentation in the Puna-Eastern Cordillera transition (23º-26ºS): Control by preexisting heterogeneities on the pattern of initial Andean shortening.

HONGN, F.; DEL PAPA, C; POWELL, J.; PETRINOVIC, I.; MON, R.; DERACO, V.

GEOLOGY

Geological Society of America

Lugar: Boulder (Colorado); Año: 2007 vol. 35 p. 271 - 274

0091-7613

The Quebrada de los Colorados Formation, at the north end of Calchaquí Valley, preserves evidence of syndepositional deformation since the Middle Eocene (~40 Ma) that includes (1) an angular unconformity with the underlying Salta Group (Paleogene), and (2) internal unconformities, changes in vertical facies succession and provenance. Its fossil record -mammalian (Notoungulates) of Middle Eocene age- is correlable to the Casa Grande Formation, which also unconformably overlies the Salta Group, so that both units record Middle Eocene deformation along the eastern border of the Puna and outline previous first-order mechanic heterogeneities related to the Cretaceous rift basin border. Along the western margin of the Puna, Eocene deformation coincides with thermal (magmatic arc) and mechanical (basin inversion) heterogeneities. Thus, the distribution of Eocene deformation followed an irregular pattern as a consequence of the heritage of preexisting heterogeneities.