Pisco Basin () is a
sedimentary basin
Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock They form when long-term subsidence ...
extending over in southwestern Peru.
[Solís Mundaca, 2018, p.1] The basin has a 2-kilometre (1.25-mile) thick sedimentary fill, which is about half the thickness of more northern
foreland basin
A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...
s in Peru.
[
The oldest known sediments are the ]Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
sandstone
Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
s of the Caballas Formation, while the youngest deposits, the fossiliferous Pisco Formation, date to the Early Pleistocene
The Early Pleistocene is an unofficial epoch (geology), sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently esti ...
.[ In relation to present-day, topography the fill of Pisco Basin makes the upper part of the Coastal Cordillera of southern Peru, the coastal plains, the Ica-Nazca Depression and the Andean foothills.
The basin is renowned for hosting various highly fossiliferous stratigraphic units; the Pisco Formation has provided a wealth of marine mammals (including sloths), birds, fish and other groups, as have the Chilcatay, Otuma and Paracas Formations.
]
Stratigraphy
Tectonic and sedimentary evolution
The basin developed in a setting of extensional tectonics
Extensional tectonics is concerned with the structures formed by, and the Tectonics, tectonic processes associated with, the stretching of a planetary body's Crust (geology), crust or lithosphere.
Deformation styles
The types of structure and the ...
from Eocene to the Late Miocene with short-lived episode of basin inversion in the Middle Miocene. Late Pliocene and Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
uplift of the basin may be consequence of the subduction of Nazca Ridge.[León et al. 2007, p. 145.]
Sedimentary strata of the basin shows evidence for a series of marine transgressions during the last 50 million years.[DeVries, 1998] These marine transgressions occurred in a sequence 41-34 Ma, 31-28 Ma, 25-16 Ma, 15-11 Ma, 10-5 Ma, and 4-2 Ma.[ The end of most of the marine transgressions is thought to be associated either with global sea level falls or compressional events in the Andes.][
]
Oligo-Miocene transgression
The marine Oligo-Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
(25–16 Ma[) marine transgression is evidenced by a series of sedimentary strata containing fossils of marine ]diatom
A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...
s, '' Peruchilus'' snails and '' Pitar'' and '' Cucullaea'' clams.[Macharé et al., 1988] Oligo-Miocene marine environments in the Pisco Basin range from littoral to shelf.[ Moquegua Basin southeast of Pisco Basin appear to have been unaffected by the transgression.][
Within the Andean margin contemporary marine transgressions are also known from southern Chile, Patagonia and Colombia.][ As such the marine transgression is thought to represent a regional phenomenon with the steadily rising central Andes being an exception.][
]
Paleontology
Pisco Formation
Chilcatay Formation
Otuma Formation
Paracas Formation
See also
* Arauco Basin, Chile
* Altiplano Basin, Peru, Chile, Bolivia
* Caldera Basin, Chile
* Cocinetas Basin, Colombia
* Urumaco Formation, Venezuela
Notes and references
Notes
References
Bibliography
;Stratigraphy
*
*
Geology publications
*
*
*
Paleontology publications
*
*
Further reading
;Chilcatay Formation
*
*
*
*
;Paracas Group
*
;Pisco Formation
*
*
*
*
*
*
*
*
*
*
*
*
*
*
{{Sedimentary basins of Peru
Sedimentary basins of Peru
Forearc basins
Paleogene Peru
Neogene Peru
Paleontology in Peru
Basins