Jama Formation

Jama Formation
Stratigraphic range: Pliocene-Early Pleistocene (Montehermosan-Ensenadan) ~
Type	Geological formation
Lithology
Primary	Claystone, sandstone
Location
Coordinates	0.2°S 80.3°W / -0.2; -80.3
Approximate paleocoordinates	0.3°S 79.9°W / -0.3; -79.9
Region	Manabí Province
Country	Ecuador
Type section
Named for	Jama
Jama Formation (Ecuador)

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

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

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