The Cocinetas Basin () is a small sedimentary basin of approximately in northeasternmost Colombia. The onshore pull-apart basin is located in the department of La Guajira at the border with Zulia, Venezuela. The basin is bound by three sets of hills; the Serranía de Jarara, Serranía Macuira and Serranía Cocinas, with the eastern boundary formed by the Gulf of Venezuela, part of the Caribbean Sea.
The basin was formed during the Paleogene as a result of the eastward movement of the Caribbean Plate along the northern edge of the South American Plate, leading to the deposition of a Middle Eocene to Middle Pleistocene sedimentary sequence of conglomerates, sandstones, siltstones, limestones and mudstones.
In the Cocinetas Basin, several fossiliferous stratigraphic units have been registered, providing an abundance of marine and continental vertebrate and invertebrate fossil fauna assemblages. The Uitpa, Jimol, Castilletes and Ware Formations contain numerous fossils of Neogene and Quaternary ages, both before and after the Great American Biotic Interchange (GABI), presenting new insights in the understanding of the variation in South American fauna related to the uplift of the Panama Block and the connection of North America and South America.
Description
The Cocinetas Basin is a small onshore sedimentary basin of approximately in the northeasternmost part of Colombia.Area Calculator Google Maps The northernmost onshore sedimentary basin of South America is clockwise bound by the Serranía de Jarara, the Macuira Fault separating the basin from the Serranía de Macuira, the Tucacas or Tortugas and Cocinetas Bays as part of the Gulf of Venezuela and the Serranía de Cocinas (in older literature referred to as Cosinas),Hernández Pardo et al., 2009, p.65 separated by the Cuisa Fault.Moreno et al., 2015, p.6
The bounding fault to the south, the dextral Cuisa Fault with a lateral displacement of ,Hernández Pardo et al., 2009, p.66 has an extension of approximately along a roughly east–west axis and the fault continues to the east underneath the Gulf of Venezuela. The fault is partly covered by Oligocene sediments.Afanador, 2009, p.38 The northern boundary of the pull-apart basin is formed by the roughly northwest–southeast-trending Macuira Fault, with an extension of about . The sinistral oblique fault has a displacement of about and uplifted the northeastern Serranía de Macuira.Rodríguez & Londoño, 2002, p.177
The basin is situated in its entirety in the municipality Uribia of the department of La Guajira. The southernmost tip of the basin borders the Venezuelan state of Zulia. The villages of Uitpa, Castilletes and Puerto López are located inside the basin.Carrillo Briceño et al., 2016, p.78Hendy et al., 2015, p.47
The present-day climate in the basin is very dry and hot (Köppen: BSh), being in the desert of La Guajira. The temperature in tropical northern South America does not vary much across the year. July is the hottest month with an average temperature of and January has a mean of . Rain is sparse throughout the year, except for October, the wettest month with of precipitation.Climate Data Uribia Alta Guajira is the driest region of Colombia and long periods of drought are common. Alta Guajira, dos años sin lluvia - El Espectador
Stratigraphy
The stratigraphy of the Cocinetas Basin was first defined by Renz in 1960. In 2015, Moreno et al. revised the stratigraphy of the basin in detail, redefining ages based on extensive fieldwork, biostratigraphy and 87Sr/86Sr isotope ratios. The basement of the basin, cropping out in the surrounding hills, is formed by the metamorphic Jarara Schist and the Paleozoic Macuira Gneiss.Plancha 3, 2008Plancha 5, 2008Plancha 10, 2008Plancha 10bis, 2008
Sedimentation in the basin started during the Middle to Late Eocene with the Macarao Formation and continued again during the Late Oligocene, when the Siamaná Formation, a sequence of conglomerates and thick carbonates, was deposited. Overlying the Siamaná Formation is the Early Miocene Uitpa Formation, a thick sequence of calcareous mudstone interbedded with lithic sandstones. The Uitpa Formation is covererd by the Miocene Jimol and Castilletes Formations, composed mostly of lithic sandstones and mudstones, that are in certain areas highly fossiliferous. The last phase of preserved sedimentation is represented by the Pliocene Ware Formation, defined in 2015 by Moreno et al.Moreno et al., 2015, p.7
The Tertiary (Paleogene to Late Pleistocene) of South America is subdivided into an own stratigraphy; the South American land mammal ages, (SALMA). This subdivision is used throughout the continent to indicate certain geologic intervals based on the occurrences of specific land mammals.South American Land Mammal Ages at Fossilworks.org
Age SALMA Formation Thickness Lithologies Notes Holocene Late Pleistocene Lujanian Mid Pleistocene Ensenadan Early Pleistocene Uquian Ware Fm. Fine lithic to quartz sandstones, mudstones, pebbly conglomerates with sedimentary and metamorphic rock fragments, fossiliferous packstones & sandy to conglomeratic beds with high fossil content Pliocene Chapadmalalan Late Miocene Montehermosan Late MioceneMid Miocene Huayquerian Chasicoan Mayoan Laventan Mid Miocene Colloncuran Castilletes Fm. Fossiliferous mudstones, siltstones & medium-grained to conglomeratic fossiliferous lithic to quartzitic sandstones Friasian Early Miocene Santacrucian Jimol Fm. Calcareous lithic & fossiliferous sandstones, siltstones & mudstones Colhuehuapian Uitpa Fm. Calcareous mudstones interbedded with lithic sandstones Late Oligocene Deseadan Siamaná Fm. Conglomerates & thick carbonates Mid Oligocene Tinguirirican Late Eocene Divisaderan Macarao Fm. Foraminifera-rich fine to medium grained calcareous sandstones intercalated with calcareous siltstones, cross-cut by veins of gypsum Middle Eocene Early Eocene Paleocene Late Cretaceous Cretaceous Jarara Schist Basement Schists & phyllites with intercalations of quartzite & localised microgabbro Jurassic Triassic Paleozoic Macuira Gneiss Basement Quartz-feldspathic, amphibolitic & biotitic gneisses, amphibolites, micaceous schists, migmatites, pegmatites & marbles
Depositional environments and correlations
The invertebrate fauna of the Jimol Formation is similar to the fauna found in the latest Early Miocene Cantaure Formation of Venezuela and the Culebra Formation of Panama.Moreno et al., 2015, p.23 The Jimol Formation was deposited in a shallow marine environment, inner shelf depth (less than water depth). This unit is correlated with the upper Agua Clara and lower Cerro Pelao Formations of the Venezuelan Falcón Basin.Moreno et al., 2015, p.27
The invertebrate fauna of the Castilletes Formation is highly similar not only to that of the underlying Jimol Formation, but also to the Cantaure Formation of Venezuela.Moreno et al., 2015, p.31 The Castilletes Formation was deposited in a shallow marine (estuarine, lagoonal, and shallow subtidal) to fluvio-deltaic environment with strong fluvial influence. The Castilletes Formation correlates with the upper Cerro Pelado and Querales Formations of the Venezuelan Falcón Basin. This unit is also correlative with the Cantaure Formation of the Paraguaná Peninsula in Venezuela.Moreno et al., 2015, p.32
The marine invertebrate fauna of the Ware Formation shows a greater similarity with modern assemblages offshore of the Guajira Peninsula than with those of the underlying units.Moreno et al., 2015, p.33 The base of the Ware Formation was deposited in a fluvio-deltaic environment, whereas the marine invertebrate assemblage at the top of the unit contains taxa typical of exposed open-ocean shoreface and nearshore settings, but with proximity to coral reef habitats. The Ware Formation correlates with the San Gregorio Formation in the Venezuelan Falcón Basin.Moreno et al., 2015, p.34
Tectonic history
Paleogeography of Colombia The tectonic history of the Cocinetas Basin, a pull-apart basin formed on top of Mesozoic basement underlain by oceanic crust, goes back to the Paleogene.Hernández Pardo et al., 2009, p.62 Farther to the south, in the Cesar-Ranchería Basin, the Paleocene, absent in the Cocinetas Basin, is represented by the first neotropic forest in the world, with megafauna as the largest recorded snake, Titanoboa cerrejonensis, with an estimated length of and a weight of , today found in the Cerrejón Formation, dated to 60 to 58 Ma. It has been estimated on the basis of the fossil flora, pollen and large reptiles that the mean annual temperature was between and yearly precipitation ranging from per year.Wing et al., 2009, p.18629
North of the Oca Fault, the oldest sedimentary sequence of the Cocinetas Basin, the Macarao Formation, is the oldest sedimentary unit of both the higher La Guajira area (the Cocinetas Basin) as well as the lower La Guajira area. This formation was deposited in a phase that is informally called "rifting", because of the formation of half grabens in the Late Eocene, though no real rifting occurred in the area.Hernández Pardo et al., 2009, p.60 Shortly after deposition, during the Early Oligocene, the Macarao Formation was heavily deformed, creating the series of hills that today still surround the Cocinetas Basin.Hernández Pardo et al., 2009, p.48 This transtensional deformation was caused by the eastward movement of the Caribbean Plate along the South American Plate, when the Caribbean volcanic arc was located just north of the Cocinetas Basin.Hernández Pardo et al., 2009, p.23 The main fault movement forming the pull-apart basin of Cocinetas was caused by the dextral Cuisa Fault, active from the Paleocene to the Eocene.
The transtensional phase of the Early Oligocene was followed by the deposition of the unconformably overlying Siamaná Formation, characterised by a basal sequence of conglomerates, indicating tectonic uplift in the provenance areas, followed by reefal limestones rich in corals and algae.Hernández Pardo et al., 2009, p.50 A new phase of transtension took place in the Early to Middle Miocene, when the Uitpa, Jimol and Castilletes Formations were deposited. The initial phase of uplift of the Isthmus of Panama, has been dated to this period, at around 12 Ma.De Porta, 2003, p.191
The Andean orogeny, represented by the tectonic uplift of the Colombian Eastern Ranges and its northern extension, the Serranía del Perijá, caused tilting and uplift in the Cocinetas Basin in the Late Miocene and Early Pliocene, when the Neogene hiatus separates the Castilletes Formation from the Ware Formation. The end of the Neogene corresponded to a marine platform setting, interrupted by the presence of a series of highs; the present-day mountain ranges of the region. Between these elevated areas, reefal limestones were deposited in a relatively quiet marine environment.Hernández Pardo et al., 2009, p.69 During the Andean orogenic phase, the paleotemperatures in the basin dropped considerably; in the Baja Guajira area from in the Early Miocene to in the Late Miocene.Hernández Pardo et al., 2009, p.122 In the Late Miocene to Pliocene, the major faults to the southwest of the Cocinetas Basin, the Oca and Bucaramanga-Santa Marta Faults were tectonically active.Hernández Pardo et al., 2009, p.28
Paleontology