Pisco Basin ( es, Cuenca de Pisco) 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 subsiden ...

extending over in southwestern Peru.Solís Mundaca, 2018, p.1 The basin has a 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 lithosphere ...

s in Peru. The oldest known sediments are the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicat ...

s of the Caballas Formation, while the youngest deposits, the fossiliferous

Pisco Formation The Pisco Formation is a geologic formation located in Peru, on the southern coastal desert of Ica and Arequipa. The approximately thick formation was deposited in the Pisco Basin, spanning an age from the Middle Miocene up to the Early Pleisto ...

, date to the

Early Pleistocene The Early Pleistocene is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy, being the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the time ...

. 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 The Nazca culture (also Nasca) was the archaeological culture that flourished from beside the arid, southern coast of Peru in the river valleys of the Nazca, Rio Grande de Nazca drainage and the Ica Valley.''The Nasca'' by Helaine Silverman and ...

and the Andean foothills. The basin is renowned for hosting various highly fossiliferous

stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize ...

s; the Pisco Formation has provided a wealth of marine mammals (including sloths), birds, fish and other groups, as have the Chilcatay, Otuma and Yumaque 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 tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend ...

from Eocene to the Late Miocene with short-lived episode of basin inversion in the Middle Miocene. Late Pliocene and

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

uplift of the basin may be consequence of the

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

Nazca Ridge The Nazca Ridge is a submarine ridge, located on the Nazca Plate off the west coast of South America. This plate and ridge are currently subducting under the South American Plate at a convergent boundary known as the Peru-Chile Trench at approxi ...

.León et al. 2007, p. 145. Sedimentary strata of the basin shows evidence for a series of

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

s 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 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 means "less recen ...

(25–16 Ma) marine transgression is evidenced by a series of sedimentary strata containing fossils of marine

diatom A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...

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.

Stratigraphy

Tectonic and sedimentary evolution

Oligo-Miocene transgression

Paleontology

Pisco Formation

Chilcatay Formation

Otuma Formation

Paracas Group

Yumaque Formation

See also

Notes and references

Notes

References

Bibliography

Geology publications

Paleontology publications

Further reading