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Tabor, Ibagué, Tolima
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Only the abstracts and keywords of the manuscripts accepted up to now have been included.
Stratigraphy and Tectonics of the Neogene and Quaternary of the Cauca Basin of Colombia
By Myriam Carlota LÓPEZ CARDONA and Luz Mary TORO TORO
October 29, 2018
The Cauca River valley is a Cenozoic intermountain basin with a tectonic history characterized by the alternation between compressional and extensional phases. Here, two new radiometric ages of the La Paila Formation are used as a reference to deduce the tectonic events that occurred in the Miocene – Quaternary interval. The Miocene – Pliocene La Paila Formation is a continental unit deposited during an extensional phase under the influence of arc volcanism. The overlying units, i.e., the Pleistocene Zarzal Formation and Quaternary deposits, record the compressive tectonic activity that started after the accretion of the Panamá Isthmus. The current deformation is registered in the Buga Salient by a series of west vergent thrust faults that are narrowing the present Cauca River valley. This salient is proposed as the western termination of the Ibagué Fault. The most recent manifestations of this deformation are the folds on Quaternary alluvial fans, which involve Holocene paleosoils, and the liquefaction of the deposits of the Zarzal Formation, which affects the overlying Quaternary deposits. On the Western Cordillera, a predominantly transcurrent tectonic style characterizes the recent deformation. It is proposed that the structure of the most recent deformation has occurred due to the indentation of a shallow continental wedge that has been introduced below the Cretaceous basement of the valley.
Keywords: La Paila Formation age, tectonic inversion, active folding, liquefaction, paleoseismicity.
Colombia in the Quaternary: An Overview of Environmental and Climatic Change
By Henry HOOGHIEMSTRA and Suzette G.A. FLANTUA
Manuscript accepted October 29, 2018
We provide an overview of environmental and climatic change in Colombia during the Quaternary, the last ca. 2.58 Ma. This period is characterised by a suite of glacial–interglacial cycles which are remarkably well documented in Colombian sediments. The distribution of Colombia’s main ecosystems has changed repeatedly driven by orbital forcing at 21, 41, and 100 ky frequencies which were superimposed by millennial–scale (ca. 2.5 ky) climate oscillations. Fossil pollen records have detected biome dynamics through time but records vary in length: the shortest comes from the Chocó rainforest (extending back to ca. 7 ka) and dry inter–Andean forest (ca. 12 ka), followed by the savannas of the Llanos Orientales (ca. 20 ka), the Amazonian rainforests (ca. 40 ka), and lower montane forest (ca. 40 ka). The longest records are from the deep sedimentary basins Bogotá (Funza09, last 2.25 Ma) and Fúquene (last 284 ka), alternatingly located in the upper montane forest and páramo during interglacial and glacial conditions, respectively. Climate change caused shifting biome distributions: mainly latitudinally in the lowlands and elevationally in the mountains. Extrinsic drivers (e.g., mean annual precipitation, length of dry season, atmospheric pCO2, mean anual temperature, freezing days) of migration and changes in vegetation composition and intrinsic drivers (such as interspecies competition and legacy effects) are still insufficiently understood, and thus hamper meaningful projections of the effect of future environmental change on biomes. Multi–site Pleistocene and Holocene information has been spatially synthesised by developing the Latin American Pollen Database. Multi–site information has been analysed by the biomisation method to serve palaeodata–model comparisons and projections about the future of biomes in Colombia. A new method in which pollen–based palaeo–reconstructions are spatially analysed with digital elevation models improved our understanding of spatial and elevational shifts of ecotones, for example the upper forest line, in the northern Andes. In the supplementary information we highlight the strengths and weaknesses in current Quaternary palaeoecological research and provide suggestions for future research.
climate change, Colombia, environmental change, pollen records, quantitative analyses, Quaternary non–analogue environments.
The Volcanic Front in Colombia: Segmentation, Recent and Historical Activity
By María Luisa MONSALVE BUSTAMANTE
Paipa Geothermal System, Boyacá: Review of Exploration Studies and Conceptual Model
By Claudia María ALFARO VALERO, Jesús Bernardo RUEDA GUTIÉRREZ, J. Camilo MATIZ–LEÓN, Miguel Angel BELTRÁN LUQUE, Gilbert Fabián RODRÍGUEZ–RODRÍGUEZ, Gina Z. RODRÍGUEZ–OSPINA, Carlos Eduardo GONZÁLEZ–IDÁRRAGA and Jaison Elías MALO LÁZARO
Manuscript accepted February 19, 2019
The Paipa geothermal system is located at 2525 m.a.s.l. in a terrain tilted from south to north towards the Chicamocha River, where the geology is dominated by sedimentary rocks intruded by felsic magmas. The mid–Pleistocene volcanic activity produced pyroclastic deposits and dome complexes. A deep saline sodium sulfate water, presumably originating from the infiltration of meteoric water followed by dissolution of an evaporite, mixes with geothermal fluid. This process masks the chemical and isotopic composition of the geothermal component of fluid discharge in hot springs, the temperatures of which reach 76 °C. Organic and magmatic/mantle contributions also affect the composition of the gas phase discharges. High concentrations of radioactive elements are found in the area, mainly in El Durazno, a highly altered intrusion located to the west. Extensive outcrops of the Une Formation at high elevation (2900 m.a.s.l.) in the Tibasosa–Toledo Anticline represent the main recharge zone. High angle faults (Las Peñas, Paipa–Iza, and Agua Tibia) and the contacts between the magmatic intrusions and the surrounding metamorphic and sedimentary rocks control the permeability of the fractured reservoir. Northward, rising hot water encounters elevated permeability in sedimentary rocks, mainly in the Une Formation, forming a sedimentary reservoir. The subsequent fluid outflow is facilitated by a normal subvertical NW fault (Cerro Plateado). Two main discharge zones, Instituto de Turismo de Paipa–Lanceros and La Playa, are controlled by intersections between faults and permeable rocks.
Stratigraphy and Geological Evolution of the Paramillo de Santa Rosa Volcanic Complex and Its Pleistocene to Holocene Eruptive History
By Bernardo Alonso PULGARÍN ALZATE, Mauricio TAMAYO ALZATE, Ana María CORREA TAMAYO, Julián Andrés CEBALLOS HERNÁNDEZ, Yeni Patricia CRUZ TORO and Ricardo MÉNDEZ FAJURY
The Nevado del Huila Volcanic Complex
By Ana María CORREA TAMAYO, Bernardo Alonso PULGARÍN ALZATE and Eumenio ANCOCHEA SOTO
Geological Evolution of the Nevado del Ruiz Volcanic Complex
By Julián Andrés CEBALLOS HERNÁNDEZ, Lilly Maritza MARTÍNEZ TABARES, Luis Gerónimo VALENCIA RAMIREZ, Bernardo Alonso PULGARÍN ALZATE, Ana María CORREA TAMAYO and Blanca Liliana NARVÁEZ MARULANDA
Holocene Lahars Deposits Associated with the Eruptive Activity of Cerro Machín Volcano, Colombia: Impact on Landscape and Associated Potential Hazard
By Gloria Patricia CORTÉS JIMÉNEZ
A Model of the Quindío and Risaralda Quaternary
By Armando ESPINOSA BAQUERO
Rear Arc Small–Scale Basaltic Volcanism in Colombia
By María Luisa MONSALVE BUSTAMANTE, Jorge GÓMEZ and Alberto NÚÑEZ TELLO
Subduction Geometries in Northwestern South America
By Carlos Alberto VARGAS
October 29, 2018
Using hypocentral solutions and arrival times of first P and S waves recorded by stations of the National Seismological Network of Colombia (NSNC), as well as GPS, gravity and magnetic public datasets, I have estimated velocity tomograms, Curie depth points and the strain field along NW South America to evaluate the subduction process and interactions of the first–order tectonic blocks. A wire model has been estimated supported by three profiles based on gravity forward modeling, earthquake distribution and b–values to elucidate the subduction behavior of the Caribbean and Nazca Plates under the South America Plate, highlighting at least three subduction scenarios, where in addition to the Caldas lithospheric tear, other minor tears are found in the lithospheric system of this region. Although it is possible a flat subduction along NW Venezuela, it is presented as an alternative hypothesis a steeper subduction, which mechanically is coherent with the structural features observed in this region. The wire model shows how the Caribbean Plate accommodates mechanically to change from flat subduction in the south to steeper subduction in the north, differentially uplifting the Santa Marta and Santander Massifs along a weakness zone that corresponds to the Santa Marta–Bucaramanga Fault System. The absence of a modern volcanic arc in the Eastern Cordillera and/or the Perijá range is a consequence of slow low–angle subduction, which is associated with the compressional regime induced by the Panamá tectonic indenter. In this scenario, I hypothesize the presence of a zone of fluid accumulation (> 130 km depth) derived from the dehydration process; these fluids cannot ascend to the surface, which impedes the formation of current active magmatism. However, during the last 9–12 Ma of relevant influence of the Panamá Arc against NW South America, other emplacements of magmatic material might have occurred along this orogenic system. The wire model also shows that the low seismic activity within the Antioquia Batholith is a consequence of its rigidity, promoting the transfer of strain derived from the subduction process from west to east, generating high seismic activity along its borders and suggesting that compositional and elastic properties at depth maintain its coherence as a structural body beyond the upper crust. A similar interpretation is indicated for the southern Eastern Cordillera.
The Algeciras Fault System of the Upper Magdalena Valley, Huila Department
By Hans DIEDERIX, Olga Patricia BOHÓRQUEZ, Héctor MORA–PÁEZ, Juan Ramón PELÁEZ, Leonardo CARDONA–PIEDRAHITA, Yuli CORCHUELO, Jair RAMÍREZ and Fredy DÍAZ–MILA
Quaternary Activity of the Bucaramanga Fault in the Departments of Santander and Cesar
Contributions of Space Geodesy for Geodynamic Studies in Colombia: 1988 to 2017
By Héctor MORA–PÁEZ, James N. KELLOGG and Jeffrey T. FREYMUELLER
Manuscript accepted October 29, 2018
Space geodetic measurements have transformed our understanding of regional tectonics in the North Andes and southwest Caribbean. The CASA (Central And South America) GPS Project, began in 1988, provided the first direct measurement of subduction at a convergent plate boundary, and it led to the establishment of a global civilian GPS tracking network. Colombia was the center of the 1988 field campaign, and the leadership of Servicio Geológico Colombiano with logistics, training, and personnel was key to the success of the CASA Project. Early GPS results showed evidence for northward movement of the North Andes, convergence at the South Caribbean deformed belt, rapid Panamá–North Andes collision, and interseismic “locking” at the Colombia–Ecuador Trench. Beginning in 2007, space geodetic measurements took a great step forward with GeoRED (Geodesia: Red de Estudios de Deformación) Project, a continuously operating GNSS network that now has 108 sites providing the first accurate comprehensive model of North Andean Block motion. Recent GeoRED findings include that the North Andean Block is moving to the northeast at a rate of 8.6 mm/yr, the Eastern Cordillera is being compressed at a rate of 4.3 mm/ yr, the Panamá Arc is colliding eastward with the North Andean Block at approximately 15–18 mm/yr, and the Panamá–Chocó collision may have been responsible for much of the uplift of the Eastern Cordillera. The new continuous GNSS measurements help to quantify tectonic deformation in northwestern South America and the southwest Caribbean, including earthquake hazards at the Colombia Trench, the Caribbean margin, the east Andean fault zone in the Eastern Cordillera, and the Panamá collision zone in northwestern Colombia; as well as the deformation of Colombian volcanoes.
Interplate Coupling along the Nazca Subduction Zone on the Pacific Coast of Colombia Deduced from GeoRED GPS Observation Data
By Takeshi SAGIYA and Héctor MORA–PÁEZ
Manuscript accepted March 5, 2019
The Nazca Plate subducts beneath Colombia and Ecuador along the Pacific coast where large megathrust events repeatedly occur. Distribution of interplate coupling on the subducting plate interface based on precise geodetic data is important to evaluate future seismic potential of the megathrust. We analyze recent continuous GPS data in Colombia and Ecuador to estimate interplate coupling in the Nazca subduction zone. To calculate the interplate coupling ratio, in addition to the MORVEL plate velocities, three different Euler poles for the North Andean Block are tested but just two of them yielded similar results and are considered appropriate for discussing the Pacific coastal area. The estimated coupling distribution shows four main locked patches. The middle two locked patches correspond to recent large earthquakes in this area in 1942, 1958, and 2016. The southernmost locked patch may be related to slow slip events. The northern locked patch has a smaller coupling ratio of less than 0.5, which may be related to the large earthquake in 1979. However, because of the sparsity of the GPS network, detailed interpretation is not possible. If we assume that the seismic moment accumulation rate is correctly estimated, the recurrence interval for a 1979–type earthquake is estimated to be ca. 124 years. More GPS data, including seafloor GPS/acoustic sensors, will greatly improve the current estimates of interplate coupling.
Mapping Land Subsidence in Bogotá, Colombia, Using the Interferometric Synthetic Aperture Radar (InSAR) Technique with TerraSAR–X Images
By Héctor MORA–PÁEZ, Fredy DÍAZ–MILA and Leonardo CARDONA–PIEDRAHITA
Integrated Perspective of the Present–Day Stress and Strain Regime in Colombia
By Mónica ARCILA and Alfonso MUÑOZ–MARTÍN