Las Juntas Formation

Geological formation in the Colombian Andes From Wikipedia, the free encyclopedia

The Las Juntas Formation or Las Juntas Sandstone (Spanish: (Formación) Areniscas de Las Juntas, Kiaj, Kialj, K1j) is a geological formation of the Altiplano Cundiboyacense and Tenza Valley, Eastern Ranges of the Colombian Andes. The Las Juntas Formation is found in the departments Cundinamarca, Boyacá and Casanare. The predominantly sandstone formation dates to the Early Cretaceous period; Hauterivian epoch, and has a maximum thickness of 910 metres (2,990 ft).

Quick Facts Type, Unit of ...
Las Juntas Formation
Stratigraphic range: Hauterivian
~132–130 Ma
TypeGeological formation
Unit ofCáqueza Group
Sub-unitsArenisca de Almeida Mb.
Lutitas Intermedias Mb.
Arenisca de El Volador Mb.
UnderliesFómeque Fm., Apón Fm.
OverliesMacanal Formation
Thicknessup to 910 m (2,990 ft)
Lithology
PrimarySandstone
OtherShale
Location
Coordinates5°00′49″N 73°27′27″W
RegionAltiplano Cundiboyacense & Tenza Valley
 Eastern Ranges
  Andes
Country Colombia
Type section
Named forCerro Las Juntas
Named byRodríguez & Ulloa
LocationGuateque
Year defined1979
Coordinates5°00′49″N 73°27′27″W
RegionBoyacá
Country Colombia
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Etymology

The formation was defined and named in 1979 by Rodríguez and Ulloa after Cerro Las Juntas, Guateque, Tenza Valley, Boyacá.[1][2]

Description

Lithologies

The Las Juntas Formation has a maximum thickness of 910 metres (2,990 ft) and is characterised by a sequence of sandstones with interbedded shales.[1]

Stratigraphy and depositional environment

The Las Juntas Formation, the uppermost unit of the Cáqueza Group, overlies the Macanal Formation and is overlain by the Fómeque Formation and the Apón Formation in the Sierra Nevada del Cocuy.[3] The formation is subdivided into three members, from old to younger; Arenisca de El Volador, Lutitas Intermedias and Arenisca de Almeida. The age has been estimated to be Hauterivian. The formation has been deposited in a near shore deltaic environment,[1][2] with as provenance areas the Santander High and the Guiana Shield.[4] The formation represents a regressive sequence in the present-day Eastern Ranges, as the Rosablanca Formation in the Middle Magdalena Valley.[5]

Outcrops

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Las Juntas Formation
Type locality of the Las Juntas Formation in the Tenza Valley east of the Altiplano Cundiboyacense

The Las Juntas Formation is apart from its type locality east of Guateque, found in Chingaza National Park,[1] in the El Cochal Synclinal east of the Ocetá Páramo,[6] between Lake Tota and Labranzagrande,[7] other parts of the Tenza Valley such as close to Macanal and Almeida.[8]

The Támara Fault thrusts the Las Juntas Formation southeastward on top of the Tertiary San Fernando and Diablo Formations,[9] and the Chámeza Fault thrusts the older Macanal Formation on top of the Las Juntas Formation around Chámeza, Casanare.[10]

Regional correlations

More information Ma, Age ...
Stratigraphy of the Llanos Basin and surrounding provinces
MaAgePaleomapRegional eventsCatatumboCordilleraproximal Llanosdistal LlanosPutumayoVSMEnvironmentsMaximum thicknessPetroleum geologyNotes
0.01Holocene
Thumb
Holocene volcanism
Seismic activity
alluviumOverburden
1Pleistocene
Thumb
Pleistocene volcanism
Andean orogeny 3
Glaciations
GuayaboSoatá
Sabana
NecesidadGuayaboGigante
Neiva
Alluvial to fluvial (Guayabo)550 m (1,800 ft)
(Guayabo)
[11][12][13][14]
2.6Pliocene
Thumb
Pliocene volcanism
Andean orogeny 3
GABI
Subachoque
5.3MessinianAndean orogeny 3
Foreland
MarichuelaCaimánHonda[13][15]
13.5LanghianRegional floodingLeónhiatusCajaLeónLacustrine (León)400 m (1,300 ft)
(León)
Seal[14][16]
16.2BurdigalianMiocene inundations
Andean orogeny 2
C1Carbonera C1OspinaProximal fluvio-deltaic (C1)850 m (2,790 ft)
(Carbonera)
Reservoir[15][14]
17.3C2Carbonera C2Distal lacustrine-deltaic (C2)Seal
19C3Carbonera C3Proximal fluvio-deltaic (C3)Reservoir
21Early MiocenePebas wetlandsC4Carbonera C4BarzalosaDistal fluvio-deltaic (C4)Seal
23Late Oligocene
Thumb
Andean orogeny 1
Foredeep
C5Carbonera C5OritoProximal fluvio-deltaic (C5)Reservoir[12][15]
25C6Carbonera C6Distal fluvio-lacustrine (C6)Seal
28Early OligoceneC7C7PepinoGualandayProximal deltaic-marine (C7)Reservoir[12][15][17]
32Oligo-EoceneC8UsmeC8onlapMarine-deltaic (C8)Seal
Source
[17]
35Late Eocene
Thumb
MiradorMiradorCoastal (Mirador)240 m (790 ft)
(Mirador)
Reservoir[14][18]
40Middle EoceneRegaderahiatus
45
50Early Eocene
Thumb
SochaLos CuervosDeltaic (Los Cuervos)260 m (850 ft)
(Los Cuervos)
Seal
Source
[14][18]
55Late PaleocenePETM
2000 ppm CO2
Los CuervosBogotáGualanday
60Early PaleoceneSALMABarcoGuaduasBarcoRumiyacoFluvial (Barco)225 m (738 ft)
(Barco)
Reservoir[11][12][15][14][19]
65Maastrichtian
Thumb
KT extinctionCatatumboGuadalupeMonserrateDeltaic-fluvial (Guadalupe)750 m (2,460 ft)
(Guadalupe)
Reservoir[11][14]
72CampanianEnd of riftingColón-Mito Juan[14][20]
83SantonianVilleta/Güagüaquí
86Coniacian
89TuronianCenomanian-Turonian anoxic eventLa LunaChipaqueGachetáhiatusRestricted marine (all)500 m (1,600 ft)
(Gachetá)
Source[11][14][21]
93Cenomanian
Thumb
Rift 2
100AlbianUneUneCaballosDeltaic (Une)500 m (1,600 ft)
(Une)
Reservoir[15][21]
113Aptian
Thumb
CapachoFómequeMotemaYavíOpen marine (Fómeque)800 m (2,600 ft)
(Fómeque)
Source (Fóm)[12][14][22]
125BarremianHigh biodiversityAguardientePajaShallow to open marine (Paja)940 m (3,080 ft)
(Paja)
Reservoir[11]
129Hauterivian
Thumb
Rift 1Tibú-
Mercedes
Las JuntashiatusDeltaic (Las Juntas)910 m (2,990 ft)
(Las Juntas)
Reservoir (LJun)[11]
133ValanginianRío NegroCáqueza
Macanal
Rosablanca
Restricted marine (Macanal)2,935 m (9,629 ft)
(Macanal)
Source (Mac)[12][23]
140BerriasianGirón
145TithonianBreak-up of PangeaJordánArcabucoBuenavista
Batá
SaldañaAlluvial, fluvial (Buenavista)110 m (360 ft)
(Buenavista)
"Jurassic"[15][24]
150Early-Mid Jurassic
Thumb
Passive margin 2La Quinta
Montebel

Noreán
hiatusCoastal tuff (La Quinta)100 m (330 ft)
(La Quinta)
[25]
201Late Triassic
Thumb
MucuchachiPayandé[15]
235Early Triassic
Thumb
Pangeahiatus"Paleozoic"
250Permian
Thumb
300Late Carboniferous
Thumb
Famatinian orogenyCerro Neiva
()
[26]
340Early CarboniferousFossil fish
Romer's gap
Cuche
(355-385)
Farallones
()
Deltaic, estuarine (Cuche)900 m (3,000 ft)
(Cuche)
360Late Devonian
Thumb
Passive margin 1Río Cachirí
(360-419)
Ambicá
()
Alluvial-fluvial-reef (Farallones)2,400 m (7,900 ft)
(Farallones)
[23][27][28][29][30]
390Early Devonian
Thumb
High biodiversityFloresta
(387-400)
El Tíbet
Shallow marine (Floresta)600 m (2,000 ft)
(Floresta)
410Late SilurianSilurian mystery
425Early Silurianhiatus
440Late Ordovician
Thumb
Rich fauna in BoliviaSan Pedro
(450-490)
Duda
()
470Early OrdovicianFirst fossilsBusbanzá
(>470±22)
Chuscales
Otengá
Guape
()
Río Nevado
()
Hígado
()
Agua Blanca
Venado
(470-475)
[31][32][33]
488Late Cambrian
Thumb
Regional intrusionsChicamocha
(490-515)
Quetame
()
Ariarí
()
SJ del Guaviare
(490-590)
San Isidro
()
[34][35]
515Early CambrianCambrian explosion[33][36]
542Ediacaran
Thumb
Break-up of Rodiniapre-Quetamepost-ParguazaEl Barro
()
Yellow: allochthonous basement
(Chibcha terrane)
Green: autochthonous basement
(Río Negro-Juruena Province)
Basement[37][38]
600NeoproterozoicCariri Velhos orogenyBucaramanga
(600-1400)
pre-Guaviare[34]
800
Thumb
Snowball Earth[39]
1000Mesoproterozoic
Thumb
Sunsás orogenyAriarí
(1000)
La Urraca
(1030-1100)
[40][41][42][43]
1300Rondônia-Juruá orogenypre-AriaríParguaza
(1300-1400)
Garzón
(1180-1550)
[44]
1400
Thumb
pre-Bucaramanga[45]
1600PaleoproterozoicMaimachi
(1500-1700)
pre-Garzón[46]
1800
Thumb
Tapajós orogenyMitú
(1800)
[44][46]
1950Transamazonic orogenypre-Mitú[44]
2200Columbia
2530Archean
Thumb
Carajas-Imataca orogeny[44]
3100Kenorland
Sources
Close
Legend
  • group
  • important formation
  • fossiliferous formation
  • minor formation
  • (age in Ma)
  • proximal Llanos (Medina)[note 1]
  • distal Llanos (Saltarin 1A well)[note 2]

See also

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

Notes

  1. based on Duarte et al. (2019)[47], García González et al. (2009),[48] and geological report of Villavicencio[49]
  2. based on Duarte et al. (2019)[47] and the hydrocarbon potential evaluation performed by the UIS and ANH in 2009[50]

References

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