The Chagres Formation (Tc)Geologic Map, 1980 is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the

Colón Province Colón () is a province of Panama. The capital is the city of Colón. It covers an area of 4,575.5 km2, and the population (in 2023) is 281,956. Overview This province has traditionally been focused on commerce (through the Colón Free Zone, ...

of central

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

. The

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 and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

s were deposited in a shallow marine environment and preserve

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the Middle to Late Miocene (

Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Tort ...

Messinian The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.333 ± 0.005 Ma (million years ago). It follows the Tortonian and is followed by the Zanclean, the fir ...

Clarendonian The Clarendonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 13,600,000 to 9,000,000 years BP, a period of . It is us ...

Hemphillian The Hemphillian North American Stage on the geologic timescale is a North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 10,300,000 to 4,900,000 years BP. It is usually considered t ...

in the NALMA classification)

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

Description

The Chagres Formation is exposed in the northern part of the

Panama Canal Zone The Panama Canal Zone (), also known as just the Canal Zone, was a International zone#Concessions, concession of the United States located in the Isthmus of Panama that existed from 1903 to 1979. It consisted of the Panama Canal and an area gene ...

. The formation overlies and partly overlaps the Gatún Formation. The outcrop area lies entirely west of the

Panama Canal The Panama Canal () is an artificial waterway in Panama that connects the Caribbean Sea with the Pacific Ocean. It cuts across the narrowest point of the Isthmus of Panama, and is a Channel (geography), conduit for maritime trade between th ...

, extending from the Canal Zone southwestward along the Caribbean coast, about southwest of Colón. Calcareous strata at the base of the formation throughout most of the outcrop area in the Canal Zone constitute the Toro limestone member.Woodring, 1957, p.47 The name Chagres Sandstone was proposed by MacDonald in 1919 for the sandstone forming the hills that overlook the coast from Toro Point to the mouth of the

Chagres River The Chagres River (), in central Panama, is the largest river in the Panama Canal's drainage basin. The river is dammed twice, and the resulting reservoirs—Gatun Lake and Lake Alajuela—form an integral part of the canal and its water ...

. The sandstone is so massive that estimates of thickness are uncertain.

Fossil content

Various fossils have been found in the Chagres Formation:Pina
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org

Fish

* ''

Alopias superciliosus The bigeye thresher (''Alopias superciliosus'') is a species of thresher shark, family Alopiidae, found in temperate and tropical oceans worldwide. Like the other thresher sharks, nearly half its total length consists of the elongated upper lobe ...

'' * '' Benthosema pluridens''Schwarzhans & Aguilera, 2013 * ''

Carcharhinus brachyurus The copper shark (''Carcharhinus brachyurus''), bronze whaler, or narrowtooth shark is a species of requiem shark found mostly in temperate latitudes. It is distributed in a number of separate populations in the northeastern and southwestern Atlan ...

'' * ''

Carcharhinus cionei ''Carcharhinus'' is the type genus of the family Carcharhinidae, the requiem sharks. One of 12 genera in its family, it contains over half of the species therein. It contains 35 extant and eight extinct species to date, with likely more species y ...

'' * '' Carcharhinus obscurus'' * '' Carcharhinus plumbeus'' * '' Carcharhinus signatus'' * '' Carcharodon plicatilis'' * ''

Centrophorus granulosus The gulper shark (''Centrophorus granulosus'') is a long and slender Squalidae, dogfish usually about three feet in length generally found in deep, murky waters all around the world. It is a light grayish brown, Countershading, paler ventrally, ...

'' * '' Cynoscion prolixus''Aguilera et al., 2016 * '' Dalatias licha'' * '' Diaphus barrigonensis'', '' D. rodriguezi'' * '' Galeocerdo cuvier'' * ''

Galeorhinus galeus The school shark (''Galeorhinus galeus'') is a houndshark of the family Triakidae, and the only living member of the genus '' Galeorhinus''. Common names also include tope, tope shark, snapper shark, and soupfin shark. It is found worldwide in t ...

'' * '' Hemipristis serra'' * ''

Heptranchias perlo The sharpnose sevengill shark (''Heptranchias perlo''), also known as one-finned shark, perlon shark, sevengill cow shark, sharpsnouted sevengill or slender sevengill, is a species of shark in the family Hexanchidae, and the only living species ...

'' * '' Heterodontus sp.'' * '' Isistius sp.'' * '' Lampadena scapha'' * '' Lepidophanes inflectus'' *

Megalodon ''Otodus megalodon'' ( ; meaning "big tooth"), Common name, commonly known as megalodon, is an extinction, extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Earl ...

* '' Mustelus sp.'' * '' Myctophum arcanum'', '' M. degraciai'' * '' Myliobatis sp.'' * '' Premontreia sp.'' * '' Pristiophorus sp.'' * '' Pseudocarcharias kamoharai'' * '' Rhizoprionodon sp.'' * ''

Sphyrna lewini The scalloped hammerhead (''Sphyrna lewini'') is a species of hammerhead shark in the family (biology), family Hammerhead shark, Sphyrnidae. It was originally known as ''Zygaena lewini''. The Greek language, Greek word ''sphyrna'' translates into ...

'' * '' Squalus sp.'' * '' Squatina sp.'' * '' Trigonognathus sp.''

Mammals

* '' Isthminia panamensis''STRI 650009
at

.orgPyenson et al., 2015 * '' Nanokogia isthmia''Vélez Juarbe et al., 2015

Invertebrates

* '' Fusiturricula fenimorei''Hendy et al., 2008

References

Bibliography

* * A. J. W. Hendy, D. P. Buick, K. V. Bulinski, C. A. Ferguson, and A. I. Miller. 2008. Unpublished census data from Atlantic coastal plain and circum-Caribbean Neogene assemblages and taxonomic opinions * * * * * {{citation , last=Woodring , first=W.P , year=1957 , title=Geology and Paleontology of Canal Zone and Adjoining Parts of Panama - 306A Geology and description of Tertiary mollusks (Gastropods: Trochidae to Turritellidae) , url=https://pubs.usgs.gov/pp/0306a/report.pdf , publisher=

USGS The United States Geological Survey (USGS), founded as the Geological Survey, is an government agency, agency of the United States Department of the Interior, U.S. Department of the Interior whose work spans the disciplines of biology, geograp ...

, pages=1–186 , accessdate=2019-02-09 Geologic formations of Panama Neogene Panama Messinian Tortonian Clarendonian Hemphillian Sandstone formations Siltstone formations Shallow marine deposits Paleontology in Panama Formations Formations