Gatuncillo Formation should not be confused with Gatún Formation.
| Gatuncillo Formation | |
| Type: | Formation |
| Age: | Middle-Late Eocene |
| Period: | Bartonian |
| Prilithology: | Mudstone, siltstone |
| Otherlithology: | Limestone, sandstone, conglomerate |
| Namedfor: | Gatuncillo River |
| Namedby: | Thompson |
| Year Ts: | 1944 |
| Region: | Panamá Province |
| Coordinates: | 9.3°N -79.7°W |
| Paleocoordinates: | 6.8°N -77.3°W |
| Underlies: | Caimito, Bohío & Panama Formations |
| Overlies: | Cretaceous basement |
| Thickness: | 150- |
| Extent: | Panama Basin |
The Gatuncillo Formation (Tgo)[1] is a geologic formation in central Panama. The formation is exposed in the Panama Canal Zone and surrounding areas. It preserves fossils dating back to the Middle to Late Eocene period.[2]
The Gatuncillo Formation is the oldest sedimentary unit of the Panama Canal Zone, unconformably resting on Cretaceous basement. The formation was defined as Gatuncillo Shale by Thompson in 1944, who named it after the Gatuncillo River. The estimated thickness ranges from 150mto800mm (490feetto2,600feetm).[3]
Though the Gatuncillo consists chiefly of mudstone and siltstone, it includes bentonitic mudstone, sandstone, and limestone, and at the base a conglomerate of variable thickness.[4]