Chapter 1

Abstract

The Cauca River valley is a Cenozoic intermountain basin with a tectonic history characterized by the alternation between compressional and extensional phases. Here, two new radiometric ages of La Paila Formation (10.5 ± 0.4 Ma and 4.4 ± 0.07 Ma Ar/Ar in amphibole) are used as a reference to deduce the tectonic events that occurred in the Miocene -Quaternary interval. The Miocene -Pliocene La Paila Formation is a continental unit deposited during an initial extensional phase under the influence of arc volcanism and a compressional final stage. The overlying units, i.e., the Pleistocene Zarzal Formation and Quaternary deposits, record the compressive tectonic activity that started after the formation of the Panamá Isthmus. The current deformation is registered in the Buga Salient by a series of west-vergent thrust faults that are narrowing the present Cauca River valley. This salient is proposed as the western termination of the Ibagué Fault. The most recent manifestations of this deformation are the folds on Quaternary alluvial fans, which involve Holocene paleosols, and the liquefaction of the deposits of the Zarzal Formation, which affects the overlying Quaternary deposits. On the Western Cordillera, a predominantly transcurrent tectonic style characterizes the recent deformation. It is proposed that the structure of the most recent deformation has occurred due to the indentation of a shallow continental wedge that has been introduced below the Cretaceous basement of the valley.

Volume 1

“…The tectonic history of the intermountain basin of the Cauca River valley, described in chapter 1 by López & Toro-Toro (2020), exhibits alternating compressional and extensional phases in the Miocene -Quaternary interval. These phases are reflected in the Miocene -Pliocene La Paila Formation depos-ited during an extensional phase influenced by arc volcanism, and the Pleistocene Zarzal Formation and Quaternary deposits that record compressive tectonic activity that initiated after the accretion of the Isthmus of Panamá.…”

Presentation

“…The tectonic history of the intermountain basin of the Cauca River valley, described in chapter 1 by López & Toro-Toro (2020), exhibits alternating compressional and extensional phases in the Miocene -Quaternary interval. These phases are reflected in the Miocene -Pliocene La Paila Formation depos-ited during an extensional phase influenced by arc volcanism, and the Pleistocene Zarzal Formation and Quaternary deposits that record compressive tectonic activity that initiated after the accretion of the Isthmus of Panamá.…”