The Gatún Formation (Tg)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 and

Panamá Province Panamá is a province of Panama. It is the location of the national capital Panama City, which also serves as the provincial capital. The governor of the province is Mayín Correa, appointed by President José Raul Mulino. Administrative di ...

s 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 formation crops out in and around 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 coastal to marginally marine

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 ...

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 ...

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

and conglomerate formation dates to the latest Serravallian to

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 ...

(

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), from 12 to 8.5 Ma.Aguilera et al., 2017, p.5Gatún Formation
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 It preserves many

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 ...

, among others,

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 ...

teeth have been found in the formation.

Description

The Gatún Formation was first defined and named as such by Howe in 1907. The formation was known before and when

William Phipps Blake William Phipps Blake (June 1, 1826 – May 22, 1910) was an American geologist, mining consultant, and educator. Among his best known contributions include being the first college trained chemist to work full-time for a United States chemical ...

traveled across Panama in 1853 on his way to California to join one of the transcontinental railroad surveying parties, he collected a few Gatún Formation fossils.Woodring, 1957, p.42 In the Canal Zone the contact between the formation with the underlying Caimito Formation is covered by the waters of Lake Gatún and even before the flooding of the lake perhaps all of the contact was concealed by swamps.Woodring, 1957, p.43 Massive medium- to very fine-grained

s and

s are the chief constituents of the Gatún Formation. They are somewhat

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

, or

marl Marl is an earthy material rich in carbonate minerals, Clay minerals, clays, and silt. When Lithification, hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. M ...

y, somewhat

aceous, and have a clay-like matrix. The sandstone contains numerous grains of black and greenish volcanic rocks and is practically a subgraywacke. Conglomerates and hard brittle very fine-grained tuff make up a small part of the formation.

Basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

intrudes older formations in the Lake Gatún area, but is not known to penetrate the Gatún Formation.

Fossil content

* '' Agatrix agathe''Landau et al., 2012 * '' Aphera aphrodite'' * '' Axelella cativa'' * '' Bivetiella dilatata'' * '' Cancellaria harzhauseri'', '' C. mixta'' * ''

Otodus 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 ...

'' * '' Carinodrillia zooki'' * '' Chilomycterus exspectatus'', '' C. tyleri'' * '' Conasprella burckhardti'', '' C. imitator'' * '' Conus (Stephanoconus) woodringi'' * '' Cryoturris habra'' * '' Cynoscion latiostialis'', '' C. scitulus''Aguilera et al., 2016 * '' Diaphus apalus'', '' D. gatunensis'' * '' Euclia alacertata'' * '' Hindsiclava consors'' * '' Lepophidium gentilis''Schwarzhans & Aguilera, 2016 * '' Leucosyrinx xenica'' * '' Massyla toulai'' * '' Pyruclia tweedledee'', '' P. tweedledum'' * '' Umbrina opima'' * '' Ventrilia coatesi''

References

Bibliography

* * * * * * * * * *

Description

Fossil content

See also

References

Bibliography

Further reading