Loma Gorda Formation

Loma Gorda Formation
Stratigraphic range: Turonian-Coniacian
~90–86.3 Ma
↓
Type Geological formation
Unit of Güagüaquí Group
Underlies Oliní Group
Overlies Hondita Formation
Thickness up to 167 m (548 ft)
Lithology
Primary Siltstone, shale
Other Calcareous concretions
Location
Coordinates 4°15′37.5″N 74°43′28.7″W / 4.260417°N 74.724639°W / 4.260417; -74.724639Coordinates: 4°15′37.5″N 74°43′28.7″W / 4.260417°N 74.724639°W / 4.260417; -74.724639
Region Upper Magdalena Valley, Central & Eastern Ranges, Andes
Country  Colombia
Type section
Named for Loma Gorda ("Fat Hill")
Named by De Porta
Location Ricaurte, Cundinamarca
Year defined 1966
Coordinates 4°15′37.5″N 74°43′28.7″W / 4.260417°N 74.724639°W / 4.260417; -74.724639
Region Cundinamarca, Huila, Tolima
Country  Colombia

Paleogeography of Northern South America
90 Ma, by Ron Blakey

The Loma Gorda Formation (Spanish: Formación Loma Gorda, 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 167 metres (548 ft).

Etymology

The formation was named in 1966 by De Porta, named Loma Gorda ("Fat Hill") in Ricaurte, Cundinamarca.[1]

Description

Lithologies

The Loma Gorda Formation is characterised by laminated siltstones and shales with calcareous concretions.[2] 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..[3]

Stratigraphy and depositional environment

The Loma Gorda Formation is the uppermost unit of the Güagüaquí Group.[1] 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.[2] Stratigraphically, the formation is time equivalent with the upper parts of the Chipaque, La Luna and La Frontera Formations.[4] 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.[5]

Outcrops

Type locality of the Loma Gorda Formation to the southwest of the Altiplano Cundiboyacense

The type locality of the Loma Gorda Formation is located close to Loma Gorda in Ricaurte, Cundinamarca.[6] Other outcrops of the Loma Gorda Formation have been noted east of the Magdalena River northeast of Honda,[7] west of Nariño, [8] west across the Magdalena River in San Luis, Tolima,[9] between the Tetuán and Saldaña Rivers west of Coyaima and east and west of Ataco,[10] to the east of the Prado River reservoir,[11] north and west of Aipe,[12] surrounding Alpujarra, Tolima,[13] south of Palermo, Huila, displaced by the Baché Fault,[14] east of Iquira,[15] north of Yaguará,[16] south of La Plata where the formation is cut by the Itaibe Fault,[17] a small patch east of Gigante, Huila,[18] northwest and northeast of San Agustín,[19] and north of Timaná surrounding the Magdalena River.[20]

Regional correlations

Cretaceous stratigraphy of the central Colombian Eastern Ranges
AgePaleomapVMMGuaduas-VélezW Emerald BeltVilleta anticlinalChiquinquirá-
Arcabuco		Tunja-
Duitama		Altiplano CundiboyacenseEl Cocuy
MaastrichtianUmir Fm.Córdoba Fm.Seca Fm.erodedGuadalupe Gp.Colón-Mito Juan Fm.
Umir Fm.
CampanianCórdoba Fm.
Oliní Gp.
SantonianLa Luna Fm.Cimarrona Fm. - La Tabla Fm.La Luna Fm.
ConiacianOliní Gp.Conejo Fm.Chipaque Fm.
Güagüaquí Gp
Loma Gorda Fm.undefinedLa Frontera Fm.
TuronianHondita Fm.La Frontera Fm.Otanche Fm.
CenomanianSimití Fm.hiatusLa Corona Gb.Simijaca Fm.Capacho Fm.
Pacho Fm.Hiló Fm. - Pacho Fm.Churuvita Fm.Une Fm.Aguardiente Fm.
AlbianHiló Fm.Chiquinquirá Sst.Tibasosa Fm.Une Fm.
Tablazo Fm.Tablazo Fm.Capotes Fm. - La Palma Fm. - Simití Fm.Simití Fm.Tibú-Mercedes Fm.
AptianCapotes Fm.Socotá Fm. - El Peñón Fm.Paja Fm.Fómeque Fm.
Paja Fm.Paja Fm.El Peñón Fm.Trincheras Fm.Río Negro Fm.
La Naveta Fm.
Barremian
HauterivianMuzo Fm.
Cáqueza Gp
Las Juntas Fm.
Rosablanca Fm.Ritoque Fm.
ValanginianRitoque Fm.Furatena Fm.Útica Fm. - Murca Fm.Rosablanca Fm.Girón Fm.Macanal Fm.
Rosablanca Fm.
BerriasianCumbre Fm.Cumbre Fm.Los Medios Fm.Guavio Fm.
Tambor Fm.Arcabuco Fm.Cumbre Fm.
Sources

See also

Geology of the Eastern Hills
Geology of the Ocetá Páramo
Geology of the Altiplano Cundiboyacense
Geology of the Middle Magdalena Valley

References

  1. 1 2 Acosta & Ulloa, 2002, p.23
  2. 1 2 Acosta & Ulloa, 2002, p.24
  3. ↑ Patarroyo, 2011
  4. ↑ Acosta & Ulloa, 2002, p.22
  5. ↑ Villamil, 2012, p.173
  6. ↑ Acosta & Ulloa, 2001, p.43
  7. ↑ Plancha 207, 2010
  8. ↑ Plancha 245, 1999
  9. ↑ Plancha 264, 2002
  10. ↑ Plancha 282, 1993
  11. ↑ Plancha 283, 2009
  12. ↑ Plancha 302, 1993
  13. ↑ Plancha 303, 2002
  14. ↑ Plancha 323, 1998
  15. ↑ Plancha 344, 1999
  16. ↑ Plancha 345, 1999
  17. ↑ Plancha 366, 1998
  18. ↑ Plancha 367, 2003
  19. ↑ Plancha 388, 2002
  20. ↑ Plancha 389, 2003

Bibliography

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