The Ucayali Basin is a Peruvian sub-Andean basin that initially formed during
the extensive tectonics of the Early Paleozoic. Originally, the Ucayali Basin was part
of a larger basin that extended east of the current Andean chain along the Peruvian
territory. Subsequently, this large basin was divided into many smaller sub-Basins
during the Andean Orogeny. Today, the basin covers an area of about 140,000 km2,
and it is morphologically defined by two well-differentiated structural features: the sub-
Andean fold and thrust belt (SFTB) to the west and the Amazon plain and Brazilian
shield to the east. It is limited to the north and south by the Contaya and Fitzcarrald
Arches respectively, the Andes to the west and the Brazilian Shield to the east. These
structural features acted as favorable elements to add sediments and to contribute to the
structural development of this basin. The sedimentary section of the basin varies in
thickness from 1 to 10 km, with ages of strata ranging from the Paleozoic to
Quaternary. The strata were deposited in deep and shallow marine as well as
transitional and fluvial continental environments. The most important phase of marine
sedimentation was initiated with the transgression of the Cretaceous sea (Aptian - Albian) over the irregular paleogeography defined by morphologic highs and
peneplains.
Tectonic features of the basin show structural deformations parallel to the
Andean front, where overturned structures are observed. These are commonly cut by
thrusts and laterally displaced by strike-slip faults.
To better understand the development of the Shira Mountains in the central part
of the Ucayali Basin, the structural and stratigraphic relationships were mapped out
using a dense grid of 2D seismic reflection data and well log control. Three regional EW
cross sections were constructed and restored to the top of the Cretaceous to
determine the nature of deformation and faulting during the Paleozoic and Mesozoic.
The reconstructions show that Shira Mountains fault was initially a major
normal fault bounding a half graben. The fault was reactivated by later compression as
a thick-skinned thrust fault that detaches between 21 and 24 km depth. Reactivation
occurred during Upper Miocene between 7.2 and 5.3 Ma, corresponding to the
Quechua 3 compressive phase of Andean Orogeny. The shortening of the central
Ucayali Basin determined by the reconstructed cross sections ranges between 3 and
5.5%.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/85841 |
| Date | 10 October 2008 |
| Creators | Sanchez Alvarez, Jaime Orlando |
| Contributors | Hopper, John |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, born digital |
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