| 词条 | Villeta Group |
| 释义 |
| name = Villeta Group | period = Coniacian | age = Aptian-Coniacian ~{{fossil range|125|87}} | image = Relieve_Villetano.jpg | imagesize = | caption = Villeta, type locality of the Villeta Group | type = Geological group | prilithology = Sandstone, shale, limestone | otherlithology = | unitof = | subunits = Conejo Fm., La Frontera Fm., Simijaca Fm., Hiló Fm., Pacho Fm., Chiquinquirá Sst., Capotes Fm., Socotá Fm., El Peñón Fm., Trincheras Fm. | underlies = Guadalupe Group | overlies = La Naveta Formation | thickness = | area = | map = Blakey 105Ma - COL.jpg | map_caption = Paleogeography of northern South America 105 Ma, {{small|by Ron Blakey}} | location | coordinates = {{coord|5|00|59|N|74|28|54|W|display=inline,title}} | region = Altiplano Cundiboyacense Eastern Ranges, Andes | country = {{COL}} | extent = | namedfor = Villeta | namedby = Hettner | year_ts = 1892 | location_ts = | coordinates_ts = {{coord|4|35|31|N|74|03|15|W|display=inline}} | paleocoordinates_ts = | region_ts = Cundinamarca, Boyacá, Huila, Santander | country_ts = {{COL}} | thickness_ts = }} The Villeta Group ({{lang-es|Grupo Villeta}}) is a geological group of the Eastern Ranges of the Colombian Andes, to the west of the Altiplano Cundiboyacense. The group, a sequence of shales, limestones and sandstones, is subdivided into various formations; Conejo, La Frontera, Simijaca, Hiló, Pacho, Chiquinquirá, Capotes, Socotá, El Peñón, and Trincheras, and dates to the Cretaceous period; Aptian-Coniacian epochs. The group stretches out across four departments, from Huila in the south, through Cundinamarca and Boyacá to southern Santander in the north. The upper part of the Villeta Group is time-equivalent with the La Luna Formation of the Middle Magdalena Valley (VMM) and Sierra Nevada del Cocuy, the Oliní and Güagüaquí Groups of the Guaduas-Vélez synclinal and the Chipaque Formation of the Altiplano Cundiboyacense. The lower part has been correlated with the Simití, Tablazo and Paja Formations of the VMM, the upper Tibasosa, Une and Fómeque Formations of the Altiplano Cundiboyacense and the Capacho, Aguardiente, Tibú-Mercedes and upper Río Negro Formations of the Sierra Nevada del Cocuy. EtymologyThe group was published in 1892 by Hettner and named after its type locality Villeta on the western flanks of the Eastern Ranges of the Colombian Andes.[1] DescriptionLithologiesThe sequence comprises an alternation of sandstones, shales and limestones and the lithologies and lateral facies variations are described in detail in the various formations comprising the group. Mineralizations of zinc, cadmium and molybdenum have been found in the Villeta Group.[1] Stratigraphy and depositional environmentThe Villeta Group overlies the La Naveta Formation and is overlain by the Guadalupe Group. The age has been estimated to be Aptian-Coniacian and the unit is subdivided into the Conejo, La Frontera, Simijaca, Hiló, Pacho Formations, the Chiquinquirá Sandstone, and the Capotes, Socotá, El Peñón, and Trincheras Formations. The core extent of the group has been defined by Cáceres and Etayo in 1969, running from Apulo in the south to Muzo in the north.[2][3] The Villeta Group has been deposited in a marine environment and the organic rich shales and pelagic limestones and cherts of the Villeta Group and equivalent units comprise 60-70% of the Cretaceous record in the Eastern Ranges. They provide a good opportunity to study the interactions between tectonics eustatic sea level and sedimentation that regulate relative sea level in a basin.[4] Outcrops{{Location map | Bogotá savanna| width = 250 | lat_deg = 5.016345 | lon_deg = -74.481596 | label = | float = left | position = right | mark = Green pog.svg | marksize = 12 | caption = Type locality of the Villeta Group to the northwest of the Bogotá savanna }} The formations of the Villeta Group are apart from its type locality near Villeta, found in other parts of the western flanks of the Eastern Ranges, stretching from Huila in the south to southern Santander in the north.[5][6][7][8][9][10][11][12][13][14][15] {{clearboth}}Regional correlations{{Cretaceous stratigraphy of the central Colombian Eastern Ranges}}See also{{portal|Colombia|Geology|Prehistory of South America|Cretaceous}}{{icon|GAN}} Geology of the Eastern Hills {{icon|B}} Geology of the Ocetá Páramo {{icon|C}} Geology of the Altiplano Cundiboyacense{{clearboth}} References1. ^Acosta & Ulloa, 2001, p.14 2. ^1 Acosta & Ulloa, 2002, p.39 3. ^Acosta & Ulloa, 2001, p.22 4. ^Villamil, 2012, p.161 5. ^Plancha 170, 2009 6. ^Plancha 171, 2009 7. ^Plancha 190, 2009 8. ^Plancha 191, 1998 9. ^Plancha 209, 2009 10. ^Plancha 210, 2010 11. ^Plancha 227, 1998 12. ^Plancha 245, 1999 13. ^Plancha 246, 1998 14. ^Plancha 264, 2000 15. ^Plancha 265, 1999 Bibliography
Maps
17 : Geological groups|Geologic formations of Colombia|Cretaceous Colombia|Upper Cretaceous Series of South America|Lower Cretaceous Series of South America|Coniacian Stage|Turonian Stage|Cenomanian Stage|Albian Stage|Aptian Stage|Reservoir rock formations|Source rock formations|Altiplano Cundiboyacense|Geography of Boyacá Department|Geography of Cundinamarca Department|Geography of Huila Department|Geography of Santander Department |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。