Boletín de Geología

Geochemical characterization of the Cretaceous Gachetá Formation, in the Casanare area, and its contribution of hydrocarbon charge as a source rock for petroleum systems present in the Llanos Orientales basin, Colombia

María Paula Cadena-Mejía — 2024-11-28

The geochemical characterization of the Gachetá Formation, based on the geochemical variables of quantity, quality and maturity of organic matter, allowed the identification of an area with greater generating potential in the west of the study area, in the Casanare department. In addition, the application of the △ log R methodology made it possible to determine the lower interval of the Gachetá Formation as the one with the highest generating potential. Crude oil analysis in the area, as well as the simulation of hydrocarbon generation and expulsion events, contributed to the identification of two oil systems, SP1: Chipaque – Guadalupe (.), from which the FCO1 family originates, and SP2: Gachetá - Mirador (.), from which the FPM family originates. Based on the above, it is postulated that the crude oils present in the platform of the Llanos Orientales Basin are the product of the mixture of the two families mentioned above, defined in this study as GPF.

Los Santos Formation in the Platanalito section: A fluvial and transgressive river-mouth estuary deposit of the Eastern Cordillera of Colombia

Fabio Laverde-Montaño — 2024-11-28

This study provides a new perspective in relation to the Los Santos Formation in the Mesas area, Eastern Cordillera of Colombia. The deposition at the base of the Los Santos Formation, referred to as Segment A, forms a coarsening-upward succession consisting of smaller entities of fining-upward type. This suggests a fluvial bay-head delta below the overlying Segment B, which is characterized by predominantly muddy succession. This lutitic domain of Segment B shows intercalated thin-bedded, very-fine-grained sandstones with double mud drapes, occasional plant remains, and the local appearance of Kinneyia. It has been interpreted as the deposit in the central part of an estuary. The presence of a tabular body of quartz sandstones, several meters thick (Segment C), observable at a distance in the landscape of the Mesas area, which develops a remarkable ravinement surface or some gullying features over the underlying lithologies at the bottomset. Segment C is mainly constituted by compound dune fields, where reactivation surfaces are oriented in the same direction as the internal stratification. These sedimentological features allow us to deduce its genesis from sediments coming from a source area located westward or southwestward, deposited obliquely or almost perpendicular to the fluvial deposit in Segment A. Segment C is interpreted as a transgressive sandy deposit at the mouth of the consolidating estuary. Subsequent minor tectonic activity reintroduces subaerial and muddy fluvial facies followed by scattered intertidal bars and channels in the fine-grained deposits of the coastal plain (Segment D). This reflects base-level fluctuations prior to the emergence of fossil-contained, tidal-influenced facies in the Cumbre Formation.

Recent tectonic activity on the western flank of the Santander massif (Colombia) from morphometric análisis

Daniel Moreno-Lozada — 2024-11-28

Nowadays, because of the available spatial information and data processing capabilities, quantitative geomorphology has become a valuable tool for assessing recent tectonic activity in structurally complex areas such as the Santander Massif. This region is characterized by low seismological and GPS data density and scarcity or absence of paleoseismological studies. It is necessary to highlight the morphological features associated with the Bucaramanga Fault and transverse NE structures. This will help identify deformation patterns and understand their kinematics, and spatial and temporal interactions. The assessment of morphometric indices on the western margin of the massif allowed for the analysis of drainage basin asymmetry, mountain front characteristics, and variations in the drainage network. The results confirm a significant tectonic activity that generates active tilting in some sectors associated with NE transverse faults, with empirical uplift rates ranging from 0.03 to 0.08 m/ka. Additionally, a counterclockwise rotation of 16.5° is observed in the hydrographic basins, with pressure ridges indicating southeastward propagation along the Bucaramanga Fault.

Gas prospectivity in the foothills domine Cordillera basin in the western foreland Llanos Orientales basin, Colombia

César Augusto Mora-Hernández — 2024-11-28

Colombia is a gas producing country that has managed to maintain a high level of self-sufficiency of this energy resource during the last 40 years, however the drastic decrease in reserves poses a worrying picture. The gas prospectivity study in the foothills domain (Cordillera basin) and the western foreland area of the Eastern Llanos basin aims to support exploration and production effort to increase gas reserves in Colombia. The geochemical characterization of gasses and the focus on the C3+ variable (propane (C3) + butane (C4) + pentane (C5)), indicates that 96% of the gas produced in the study area is of wet character (C3+ above 5%) and is a source of both natural gas (NG-Methane) and liquefied petroleum gas (LPG- propane-butane). The combination associated the source rock potential, thermal maturity level of the source rocks and the origin of the gas associated to primary cracking processes, allowed ideal conditions for the trapping and production of light oil, condensates, wet gas (LPG source) and dry gas (NG). Based on the integration of the results, four prospectivity play fairways are proposed: foothills, where the largest gas production in Colombia is located (NG and LPG), foredeep (deep zone of the foreland basin). In all the play fairways there are discovered oil and gas fields with production histories of more than 30 years and in the process of decline, which have a well-developed oil infrastructure. Since most of the gas is associated with oil, the increase of gas reserves in the foothills domain and the foreland of the Llanos Orientales basin depends on an integrated exploration strategy that includes both oil and gas.

Discrimination of the climate, relief, and tectonic relationship in a sector of the Eastern Basin, Eastern Cordillera of Colombia through geomorphology and quantitative thermochronology

Lady Alejandra Barrera-Chaparro — 2024-11-28

At the Colombian Eastern Cordillera, we focused on the Arcabuco Anticline, which is an asymmetric fold with a core of Jurassic sedimentary rocks. The region considered includes the active reverse faults of Soapaga and Boyacá, the activity of these faults, the geomorphological evolution and its relationship with the current erosion of this area have been little studied. By applying quantitative geomorphology, the relationship between climate, relief, and tectonics, as well as the possible coupling of these processes, was distinguished. For this purpose, the study incorporated data on precipitation, relief, hypsometric integral (HI), steepness index, seismicity, and thermochronological. Using statistical comparison of the different calculated variables, it is concluded that tectonic activity, primarily resulting from the interaction of the Boyacá and Soapaga faults, is determining the shaping of the current relief. Additionally, the geomorphometric analysis allowed for the discrimination of basins at different evolutionary stages. The Chicamocha Basin is in a senile stage (HI=0.27), while the Huertas, Pómeca, and Tolotá Basins are in a mature stages (HI=0.34, HI=0.44, HI=0.31, respectively).

Geometric and kinematic analysis of the Puquín anticline, Cusco – Perú

Yessenia Puma-Enriquez — 2024-11-28

The Puquín anticline is a geological structure located in the Cusco region that extends ~9.8 km. In the core of the anticline, sedimentary rocks of the Puquín Formation are exposed. Likewise, sedimentary rocks of the Quilque, Chilca, Kayra and Soncco formations outcrop on the flanks of the anticline. It is an asymmetric fold with a N-S fold axis strike, closed in the northern and central portion and open in the southern portion, and has a double dip axis of approximately 21°S and 34°N. The front flank shows greater thickening than the rear flank and is traversed by a backthrust. Based on these features, the Puquín anticline is interpreted as a fault-propagation fold. The shortening calculated from three structural sections, carried out by the trishear method, is 8.32 km (15.1%), 8.61 km (12.1%) and 8.62 km (12.0%) for the northern, central and south cross-sections, respectively. The analysis of the pattern of fractures, faults and veinlets carried out in 23 structural stations in different sectors of the anticline made it possible to distinguish 5 sets of orientations: WNW-ESE, NNE-SSW, W-E, NE-SW and WSW-ENE. These structures are compatible with the structural arrangement that originates in the folds and in this case with the Puquín fold.

Paleoenvironments in the central San Jacinto Fold Belt (Colombian Caribbean) during the late Eocene and early Miocene: inferences from benthic foraminífera

Raúl Trejos-Tamayo — 2024-11-28

The distribution of benthic foraminifera from the upper Eocene to lower Miocene interval was studied in a marine sedimentary succession recorded by the ANH-SAN JACINTO-1 well, located in the central San Jacinto Fold Belt (Colombian Caribbean). The study included the estimation of diversity, the ratio between calcareous and agglutinated benthic foraminifera, the planktonic to benthic (P/B) ratio, the distribution of dissolved oxygen indicators, and morphogroup analysis, aiming to understand the paleoenvironmental evolution of the succession. During the upper Eocene, the lithological transition from calcareous sandstones and limestones to black mudstones indicates a discordant contact between the San Jacinto and El Carmen formations. In the San Jacinto Formation, calcareous benthic foraminifera predominate, and the low P/B ratio indicates shelf environments with a constant nutrient flux and suboxic bottoms influenced by turbiditic currents. In contrast, at the onset of the El Carmen Formation, the P/B ratio increases, indicating deeper conditions typical of the slope. The predominance of agglutinated foraminífera suggests corrosive bottom waters, likely below the lysocline and the calcite compensation depth (CCD). This scenario aligns with the global cooling during the late Eocene when the CCD was shallower. In the early Oligocene, a resurgence of calcareous foraminifera occurred, coinciding with the global deepening of the lysocline and/or the CCD, which allowed their preservation. During this interval, the assemblages indicates mesotrophic bottom waters with low oxygen levels. During the late Oligocene and early Miocene, benthic foraminifera indicate increased nutrient availability, reflecting a transition to more eutrophic conditions in bottom environments.

Gerardo Botero: The human being

Natalia Hoyos — 2024-11-28

This work presents the profile of Gerardo Botero Arango (1911-1986) from his multiple facets as a scientist, teacher, engineer, colleague, friend, and family member, based on his academic and personal correspondence, as well as memories of his closest relatives, as a tribute to commemorate the 60th anniversary of the publication of his work “Contribution to the knowledge of the geology of the central zone of Antioquia” (Botero 1963). Although formally trained as a Civil and Mining Engineer, his scientific interests spanned various branches of the natural sciences, including paleontology, stratigraphy, petrography, and regional geology. He published research in these areas over half a century (1934-1983) in collaboration with local and international colleagues. His professional and personal life were characterized by his vision, knowledge, pragmatism, and unwavering ethics, framed in a personality far from any search of recognition.

Uplift and denudation of the Antioquia Eastern Massif (Colombia) from fission-tracks thermochronology

Edgar Alland Saenz-Mateus — 2024-11-28

Fission-track dating and thermochronology have been used to assess the low-thermal history of some plutonic rocks intruded into the Antioquia Eastern Massif as defined by Gerardo Botero. These techniques enable us to gain a better understanding of the orogenic process that shaped the northern Colombian Central Cordillera. Samples were collected from the Antioqueño Batholith, Sonsón Batholith, and the smaller igneous bodies: La Unión, San Diego, Altavista and Ovejas, all intruded during the Late Cretaceous. Zircon fission track ages vary from 46.4±1.1 Ma to 64.0±1.3 Ma. Mean track lengths are very homogeneous, with variations from 13.9±1.6 μm to 14.6±1.3 μm. The results of thermal annealing modeling carried out with the AFTSolve program show three main segments: 1) Significant decrease in temperature from 240°C to ~50°C in the middle to late Eocene at maximum cooling rates of 50°C/Ma; 2) A period of thermal stability extending into the Middle Miocene; and 3) a final cooling segment through to surface temperature (20°C) at cooling rates of about 4°C/Ma. Results were interpreted as coincident with the Pre-Andean (middle Eocene) and the Eu-Andean (late Miocene-Pliocene) orogenies. This last pulse is related to the recent orogeny that exhumed the analyzed samples, occurring between 3 and 5 Ma ago, interpreted as the maximum time for the formation of the “Central Cordillera” erosion surface and its subsequent superimposed relief. The intermediate quiescent period did not record the Oligocene Proto-Andean orogeny. The tectonic phases produced episodes of uplift and denudational response at maximum rates of 2000 and 160 m/ Ma, respectively, using an assumed geothermal gradient of 25ºC/km.

From rock decomposition to soil formation: a paradigm shift in the teaching of geology in Antioquia, Colombia (1887-1965)

Susana Salazar — 2024-11-28

When “Contribución al conocimiento de la geología de la zona central de Antioquia” by Gerardo Botero Arango was published in 1963 in Anales de La Facultad de Minas, knowledge of weathering processes in Antioquia was limited. Although this work introduced an approach to exogenous processes, attention to chemical weathering in the region did not emerge until the thesis of his student, Michel Hermelin Arbaux, in 1965. Chemical weathering, which plays a key role in the formation of materials such as regoliths, saprolites, and soils, as well as in landscape evolution, only gained recognition in Colombia during the second half of the 20th century. Consequently, Michel Hermelin Arbaux's thesis, Estudio preliminar sobre la descomposición de algunas rocas del Batolito Antioqueño, along with subsequent research on chemical weathering, has greatly enriched our understanding of how these processes influence landscape and soil formation in Antioquia and, more broadly, throughout Colombia. IOriginally introduced by geologists but extensively developed by pedologists and geomorphologists, this new knowledge and awareness of surface processes have enhanced our understanding of tropical geomorphology and environmental geology in the country. This article reviews the historical context of earth science education at the then National School of Mines (1887-1940), the importance of exogenous processes in a holistic view of geology, and their impact on applied geology in Antioquia. Encouraged by Gerardo Botero Arango, the study of the “decomposition (sic)” of the rocks of the Antioquian Batholith went beyond a simple examination of chemical weathering; it was a pioneering effort in Antioquia and that underscored the differences in materials, processes, and landforms between tropical and temperate regions.

Considerations on the crustal seismic structure in the northernmost Central Cordillera of Colombia – “Altiplano Antioqueño”

Gaspar Monsalve — 2024-11-28

The “Altiplano Antioqueño” (Antioquia Plateau) is located in the northern portion of the Central Cordillera of Colombia, and comprises a series of erosion surfaces geologically dominated by the Antioquia Batholith. The nature of the crustal deformation in the area is still enigmatic. In this contribution we integrate various elements to elucidate the seismic structure of the crust, including the use of the seismological receiver function technique to estimate crustal thickness, the analysis of instrumental seismicity, and the calculation of focal mechanisms for earthquakes in the area with magnitudes greater than 3; the integration of these observations with current knowledge of the lithologies and the regional faults, facilitates a better approximation of the crustal structure and the nature of the present deformation. In particular, teleseismic receiver functions suggest crustal thicknesses between 45 and 55 km, especially in the western flank of the plateau; the receiver functions do not provide conclusive data regarding crustal thickness near its eastern boundary. The instrumental seismicity shows a concentration of earthquakes along the borders of the Antioquia Batholith, with a relative absence of seismicity within this body. The focal mechanisms indicate thrust faulting at the western border of the batholith, whereas at the eastern border they show strike-slip faulting.

A preliminary assessment of the topography of Botero’s Central Zone of Antioquia (Colombian Andes) via wavelet transforms

Sergio Andrés Restrepo-Moreno — 2024-11-28

The classic work “Contribución al conocimiento de la geología de la zona central de Antioquia” by Dr. G. Botero (1963) addressed for the first time important morpho-climatic aspects in the northern portion of the Central and Western mountain ranges, incorporating altimetry, geomorphology, tectonics and climate as geological elements that shape a key morpho-tectonic province in the Northern Andes: the Antioquia Altiplano (AA) in the Eastern Massif (OM) of Antioquia, sensu Botero, and the canyon of the Medellín-Porce river that dissect it, and the Cauca and Magdalena rivers that delimit it to the west and east respectively. Given the technological restrictions at the time, Dr. Botero was unable to address these topics based on digital analysis of the terrain. His work was mainly descriptive-qualitative and focused on establishing genetic elements in the evolution of the landscape. We present a preliminary proposal for using digital elevation models (DEM-SRTM) and GRASS tools and R extensions, to facilitate a quantitative-geomorphometric treatment of the terrain to address the topographic expression of AA-MO as a set of periodic-quasiperiodic signals, specifically through wavelet transforms. We preliminarily evaluate the role of the Haar wavelet transform both in a synthetic relief and a real case study on a portion of the MO, incorporating elements of the AA and the canyons/valleys of the Medellín and Cauca rivers. The dyadic DEM segment of the MO (~512×512 pixels of 90×90 m) enabled the preliminary dissection of the landscape, without loss of spatial information, into several levels, each containing landforms within a similar scale domain in space-frequency. Our approach holds promise for analyzing diverse landforms, including composites of hills, valleys and plateau systems. This pioneering application of wavelets to geomorphology problems in Colombia demonstrates the potential of these novel methods for decompositions and recompositions under GRASS-R is demonstrated.