The Loma Gorda Formation (, Kl, Kslg) is a fossiliferous geological formation of the Upper Magdalena Valley (VSM) and surrounding Central and Eastern Ranges of the Colombian Andes, extending from Cundinamarca in the north to Huila and easternmost Tolima in the south. The uppermost unit of the Güagüaquí Group, a sequence of laminated siltstones and shales, dates to the Late Cretaceous period; Turonian to Coniacian epochs, and has a maximum thickness of .
Etymology The formation was named in 1966 by De Porta, named Loma Gorda ("Fat Hill") in Ricaurte, Cundinamarca.Acosta & Ulloa, 2002, p.23
Description Lithologies The Loma Gorda Formation is characterised by laminated siltstones and shales with calcareous concretions.Acosta & Ulloa, 2002, p.24 The formation has provided fossils of Ankinatsytes venezolanus, Barroisiceras onilahyense, Codazziceras ospinae, Eulophoceras jacobi, Fagesia catinus, Hauericeras madagascarensis, Hoplitoides ingens, H. lagiraldae, Mitonia gracilis, Mytiloides kossmati, M. goppelnensis, M. scupini, Neoptychites cf. andinus, Paralenticeras sieversi, Paramammites sp., Peroniceras subtricarinatum, Prionocycloceras guayabanum, Reesidites subtuberculatum, Subprionotropis colombianus, Allocrioceras sp., Anagaudryceras sp., Anomia sp., Benueites sp., Choffaticeras sp., Dydimotis sp., Forresteria sp., Gauthiericeras sp., Morrowites sp., Nannovascoceras sp., and Quitmaniceras sp..Patarroyo, 2011
Stratigraphy and depositional environment The Loma Gorda Formation is the uppermost unit of the Güagüaquí Group. It overlies the Hondita Formation and is overlain by the Oliní Group. The age has been estimated on the basis of ammonites to be ranging from Turonian to Coniacian. Stratigraphically, the formation is time equivalent with the upper parts of the Chipaque, La Luna and La Frontera Formations.Acosta & Ulloa, 2002, p.22 The formation was deposited in a relative highstand sequence with an oceanic oxygen depletion event, sharply marked in Colombia and characterised by the appearance of calcareous concretions with a thick pyrite rim.Villamil, 2012, p.173
Outcrops
The type locality of the Loma Gorda Formation is located close to Loma Gorda in Ricaurte, Cundinamarca.Acosta & Ulloa, 2001, p.43 Other outcrops of the Loma Gorda Formation have been noted east of the Magdalena River northeast of Honda,Plancha 207, 2010 west of Nariño,Plancha 245, 1999 west across the Magdalena River in San Luis, Tolima,Plancha 264, 2002 between the Tetuán and Saldaña Rivers west of Coyaima and east and west of Ataco,Plancha 282, 1993 to the east of the Prado River reservoir,Plancha 283, 2009 north and west of Aipe,Plancha 302, 1993 surrounding Alpujarra, Tolima,Plancha 303, 2002 south of Palermo, Huila, displaced by the Baché Fault,Plancha 323, 1998 east of Iquira,Plancha 344, 1999 north of Yaguará,Plancha 345, 1999 south of La Plata where the formation is cut by the Itaibe Fault,Plancha 366, 1998 a small patch east of Gigante, Huila,Plancha 367, 2003 northwest and northeast of San Agustín,Plancha 388, 2002 and north of Timaná surrounding the Magdalena River.Plancha 389, 2003
Regional correlations
See also
Geology of the Eastern Hills Geology of the Ocetá Páramo Geology of the Altiplano Cundiboyacense Geology of the Middle Magdalena Valley
Notes
References
Bibliography
Maps
External links