Earth:Loma Gorda Formation

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Short description: Geological formation in the Colombian Andes
Loma Gorda Formation
Stratigraphic range: Turonian-Coniacian
~90–86.3 Ma
↓
TypeGeological formation
Unit ofGüagüaquí Group
UnderliesOliní Group
OverliesHondita Formation
Thicknessup to 167 m (548 ft)
Lithology
PrimarySiltstone, shale
OtherCalcareous concretions
Location
Coordinates [ ⚑ ] : 4°15′37.5″N 74°43′28.7″W / 4.260417°N 74.724639°W / 4.260417; -74.724639
RegionCundinamarca, Huila & Tolima
Country Colombia
ExtentUpper Magdalena Valley, Central & Eastern Ranges, Andes
Type section
Named forLoma Gorda ("Fat Hill")
Named byDe Porta
LocationRicaurte, Cundinamarca
Year defined1966
Coordinates [ ⚑ ] 4°15′37.5″N 74°43′28.7″W / 4.260417°N 74.724639°W / 4.260417; -74.724639
RegionCundinamarca, Huila, Tolima
Country Colombia
Blakey 090Ma - COL.jpg
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

Lua error in Module:Location_map at line 522: Unable to find the specified location map definition: "Module:Location map/data/Altiplano Cundiboyacense" does not exist. 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

See also

Featured article candidate Geology of the Eastern Hills
B-Class article Geology of the Ocetá Páramo
C-Class article Geology of the Altiplano Cundiboyacense
C-Class article Geology of the Middle Magdalena Valley

Notes

References

  1. ↑ 1.0 1.1 Acosta & Ulloa, 2002, p.23
  2. ↑ 2.0 2.1 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

Maps

External links



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