Jama Formation

The Jama Formation is a Pliocene to Early Pleistocene (Montehermosan to Ensenadan in the SALMA classification) geologic formation in Ecuador. The claystones and sandstones were deposited in an coastal environment. The age of the Jama Formation is constrained by ⁴⁰Ar/³⁹Ar dating of tephra beds.[1] The formation is correlated to the Charco Azul Formation of western Panama and southeastern Costa Rica.[2]

Jama Formation Stratigraphic range: Pliocene-Early Pleistocene (Montehermosan-Ensenadan) ~5.3–0.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Lithology
Primary	Claystone, sandstone
Location
Coordinates	0.2°S 80.3°W
Approximate paleocoordinates	0.3°S 79.9°W
Region	Manabí Province
Country	Ecuador
Type section
Named for	Jama
Jama Formation (Ecuador)

Subdivision

The formation is subdivided in, from top to base:

• El Matal Member (60 metres (200 ft), fluvial)
• Punta Ballena Member (lower shoreface)
• Punta Pasa Borracho Member (20 metres (66 ft), marine)

Fossil content

The formation has provided bivalve, gastropod and scaphopod fossils.

See also

• List of fossiliferous stratigraphic units in Ecuador

References

1. Jama Formation at Fossilworks.org
2. Charco Azul Formation at Fossilworks.org

Further reading

• G. Cantalamessa, C. Di Celma, and L. Ragaini. 2005. Sequence stratigraphy of the Punta Ballena Member of the Jama Formation (Early Pleistocene, Ecuador): insights from integrated sedimentologic, taphonomic and paleoecologic analysis of molluscan shell concentrations. Palaeogeography, Palaeoclimatology, Palaeoecology 216:1-25
• H. A. Pilsbry and A.A. Olsson. 1941. A Pliocene fauna from Western Ecuador. Proceedings of the Natural Sciences of Philadelphia 93:1-79