Floresta Formation

Floresta Formation
Stratigraphic range: Late Emsian-Early Givetian
~400–387 Ma

Platyceras nodosum from the Floresta Formation
Type Geological formation
Underlies Cuche Formation
Overlies El Tibet Formation
Thickness up to 600 m (2,000 ft)
Lithology
Primary Siltstone
Other Shale, coquina, sandstone
Location
Coordinates 5°51′37.2″N 72°56′57.6″W / 5.860333°N 72.949333°W / 5.860333; -72.949333Coordinates: 5°51′37.2″N 72°56′57.6″W / 5.860333°N 72.949333°W / 5.860333; -72.949333
Region Altiplano Cundiboyacense
Eastern Ranges, Andes
Country  Colombia
Type section
Named for Floresta
Named by Olsson & Carter
Location Floresta
Year defined 1939
Coordinates 5°51′37.2″N 72°56′57.6″W / 5.860333°N 72.949333°W / 5.860333; -72.949333
Approximate paleocoordinates 51°42′S 48°06′W / 51.7°S 48.1°W / -51.7; -48.1
Region Boyacá
Country  Colombia
Thickness at type section 600 m (2,000 ft)

Paleogeography of the Middle Devonian
380 Ma, by Stampfli & Borel

The Floresta Formation (Spanish: Formación Floresta, Df) is a geological formation of the Altiplano Cundiboyacense in the Eastern Ranges of the Colombian Andes. The sequence of siltstones, shales, coquinas and sandstone beds dates to the Devonian period; Late Emsian, Eifelian and Early Givetian epochs, and has a maximum thickness of 600 metres (2,000 ft). The unit is highly fossiliferous; brachiopods, bryozoans, gastropods, trilobites, corals and bivalves have been found in the Floresta Formation. Some fragments of Placoderm fish fossils were found in the Floresta Formation, while the overlying Cuche Formation is much richer in fish biodiversity.

Etymology

The formation was first described as Floresta Series by Olsson and Carter in 1939. The current definition was given by Botero in 1950. The formation is named after Floresta, Boyacá, where the formation outcrops.[1]

Description

Lithologies

The Floresta Formation is characterised by a lower sequence of shales and ochre to beige siltstones with alternating coquinas, while the upper part consists of siltstones with sandy beds.[2]

Stratigraphy and depositional environment

The Floresta Formation overlies the El Tibet Formation and is overlain by the Cuche Formation. The age has been estimated to be Late Emsian to Early Givetian.[3] Stratigraphically, the formation is time equivalent with the Portachuelo Formation around Quetame.[4] The Onondaga Formation of New York is considered time equivalent too.[5] The formation contains concretions and a high diversity of fossils. The formation was deposited in a transgressional and regressional epicontinental marine environment at the edge of the Paleo-Tethys Ocean.[6] The uppermost part of the formation has been deposited in a deltaic setting,[7] with the lower sequence formed in a coral reef environment.[8]

Fossil content

Remains of Barroisella sp.,[9] ?Tarutiglossa sp.,[10] Dipleura cf. dekayi, Dechenella boteroi,[11] Mannopyge sp., Cordania gasepiou, Viaphacops cristata,[12] Anchiopsis armata,[13] Synphoria stemmata, Coronura cf. lessepsensis,[14] Greenops cf. grabaui,[15] Belenopyge contusa, Kettneraspis callicera,[16] Placoderm fishes,[17] Platyceras nodosum,[18] Acrospirifer olssoni, Anoplotheca cf. silvetii, Atrypa harrisi, Australospirifer cf. antarcticus, Aviculopecten wellsi, Brachyspirifer palmerae, Camarotoechia dotis, Chonetes cf. billingsi, C. comstockii, C. cf. stubeli, Chonostrophia knodi, Cyclotrypa boyaca, C. carribeana, C. dickeyi, C. reticulata, C. stellata, Cymostrophia dickeyi, C. schucherti, C. waringi, Cypricardinia cf. subindenta, Cyrtina hamiltonensis, Dalmanites cf. patacamayaensis, Dictyostrophia cooperi, Elytha colombiana, Eodevonaria imperialis, Favosites aff. hamiltonensis, Fenestrellina colombiana, F. olssoni, F. acuta, F. quadrata, F. harrisi, Fistulipora anomala, F. megalopora, Florestacanthus morenoi, Heliophyllum halli,[18] Intrapora fragilis, I. megalopora, Leiorhynchus mysia, Leptaena boyaca, Meganteris australis, Megastrophia hopkinsi, M. pygmaea, Meristella wheeleri, Nucleospira concinna, Odontopleura callicera, Pentagonia gemmisulcata, Phacops cf. salteri, Pholidops florestae, Platyostoma lineata, Pleurodictyum americanum, Polypora elegantula, P. granulifera, Prismopora inornata, Schellwienella goldringae, Semicoscinium colombiensis, S. minutum, Spinocyrtia cf. valenteana, Spinulicosta spinulicosta, Spirifer kingi, Strophonella floweri, S. meridionalis, Sulcoretepora olssoni, S. subramosa, Taeniopora florestae, Tropidoleptus carinatus, Unitrypa casteri, Acanthograptus sp., Actinopteria sp, Amphigenia sp., Anthozoa sp., Camarotoechia sp., Cryptonella sp., Cyphaspis sp., Cryphaeus sp., Dalmanites sp., Derbyina sp., Gastropoda sp., Grammysia sp., Homalonotus sp., Leptostrophia sp., Mediospirifer sp., Orthoceras sp., Ostracoda sp., Orthis sp., Paraspirifer sp., Proetus sp., Pterinea sp., Strophodonta sp., Thamnopora sp., and Vitulina sp. have been described from the Floresta Formation.[19] Colombianaspis carvalhoae gen. et sp. nov., Schizobolus pilasiensis sp. nov. and Tarijactinoides sp. nov.,[16] were newly described in 2015.[3]

Outcrops

Type locality of the Floresta Formation in the north of the Altiplano Cundiboyacense

The Floresta Formation is found at the Floresta Massif around its type locality in Floresta, Boyacá,[20] stretching to the south until between Busbanzá and Nobsa and to the west close to Belén, Cerinza and Tutazá.[21]

See also

Geology of the Eastern Hills
Geology of the Ocetá Páramo
Geology of the Altiplano Cundiboyacense

References

  1. ↑ Mojica & Villarroel, 1984, p.64
  2. ↑ Morzadec et al., 2015, p.332
  3. 1 2 Morzadec et al., 2015, p.355
  4. ↑ Morzadec et al., 2015, p.331
  5. ↑ Giroud López, 2014, p.168
  6. ↑ Janvier & Villarroel, 1998, p.6
  7. ↑ Giroud López, 2014, p.169
  8. ↑ Giroud López, 2014, p.170
  9. ↑ Morzadec et al., 2015, p.335
  10. ↑ Morzadec et al., 2015, p.336
  11. ↑ Morzadec et al., 2015, p.340
  12. ↑ Morzadec et al., 2015, p.342
  13. ↑ Morzadec et al., 2015, p.344
  14. ↑ Morzadec et al., 2015, p.346
  15. ↑ Morzadec et al., 2015, p.348
  16. 1 2 Morzadec et al., 2015, p.352
  17. ↑ Janvier & Villarroel, 1998, p.9
  18. 1 2 Giroud López, 2014, p.39
  19. ↑ Floresta at Fossilworks.org
  20. ↑ Mojica & Villarroel, 1984, p.70
  21. ↑ Plancha 172, 1998

Bibliography

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