Examinando por Materia "Foraminifera"
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Ítem Automatic identification of foraminiferal associations and their paleoenvironmental implications, Galembo Member of the La Luna Formation, Colombia(Universidad EAFIT, 2022) Grateron Estrada, Mayra Alejandra; Beltrán Triviño, Alejandro Iván; Páez Reyes, Manuel Arnulfo; San Martín Cañas Janowsky, StephanieÍtem Dinámica costera durante el Mioceno tardío - Plioceno temprano al norte del Cinturón Plegado Sinú - San Jacinto, Colombia(Universidad EAFIT, 2021) Cárdenas Gómez, Claudia Patricia; Cárdenas Rozo, Andrés Leonardo; Rincón Martínez, Daniel AndrésÍtem Los Dinoflagelados del Mioceno Medio Alto - Mioceno Superior del Caribe Colombiano: taxonomía, bioestratigrafía e implicaciones geológicas(Universidad EAFIT, 2006) Medina Campos, Liliana; Martínez Rodríguez, José IgnacioDel estudio palinológico del intervalo Mioceno Medio alto – Mioceno Superior, para el Caribe Colombiano se reporta, por primera vez, la ocurrencia de 42 morfotipos de dinoflagelados (22 Gonyaulacales, 19 Peridiniales y 1 del tipo Mixto) con una mayor abundancia de Gonyaulacales en el Valle Inferior del Magdalena y mayor abundancia y diversidad de Peridiniales en la Baja Guajira, coincidiendo esto último, con la diversificación de los Peridiniales durante el Neógeno -- Se reconocen 6 posibles zonas de dinoflagelados en el intervalo Mioceno Medio alto – Mioceno Superior, incrementando así la resolución bioestratigráfica basada en foraminíferos planctónicos y polen -- La variación del índice Peridiniales/Gonyaulacales (P/G), en relación con el porcentaje de Globorotálidos y Neogloboquadrínidos (foraminíferos de aguas profundas), sugieren el sostenimiento de condiciones ricas en nutrientes asociadas con descargas fluviales en el Valle Inferior del Magdalena y sistemas de surgencia en la Baja Guajira -- Las condiciones paleoceanográficas en el área de la Baja Guajira durante el Mioceno Tardío habrían sido análogas a las actuales, sugiriendo así el posible inicio del actual sistema de surgencia de la Guajira para este tiempo -- Para el Valle Inferior del Magdalena se sugieren ambientes de depósito someros para la Unidad Porquero Superior durante el Mioceno Medio tardío, y ambientes de paleodelta para la Unidad Tubará durante el Mioceno Tardío -- En la Baja Guajira se sugieren ambientes de plataforma en la parte alta de la Formación Jimol durante el Mioceno Medio, con ambientes someros (plataforma interna?) hacia la Formación Castilletes durante el Mioceno TardíoÍtem Foraminifera and coccolithophorid assemblage changes in the Panama Basin during the last deglaciation: Response to sea-surface productivity induced by a transient climate change(ELSEVIER SCIENCE BV, 2006-05-03) Martinez, Ignacio; Rincon, Daniel; Yokoyama, Yusuke; Barrows, Timothy; Universidad EAFIT. Departamento de Geología; Ciencias del MarThe responses of community assemblages of planktonic and benthonic foraminifera and coccolithophorids to transient climate change are explored for the uppermost 2 m of cores ODP677B (1.2°N; 83.74°W, 3461 m) and TR163-38 (1.34°S; 81.58°W, 2200 m), for the last ~ 40 ka. Results suggest that the deglaciation interval was a time of increased productivity and a major reorganization of planktonic trophic webs. The succession in dominance between the planktonic foraminifera species Globorotalia inflata, Globigerina bulloides, and Neogloboquadrina pachyderma denote four periods of oceanographic change: (1) advection (24-20 ka), (2) strong upwelling (20-15 ka), (3) weak upwelling (14-8 ka) and (4) oligotrophy (8 ka to present). Strong upwelling for the deglaciation interval is supported by the low Florisphaera profunda/other coccolithophorids ratio and the high percentage abundance of Gephyrocapsa oceanica. Benthonic foraminifera assemblage changes are different in both cores and suggest significant regional variations in surface productivity and/or oxygen content at the seafloor, and a decoupling between surface productivity and export production to the seafloor. This decoupling is evidenced by the inverse relationship between the percentage abundance of infaunal benthonic foraminifera and the percentage abundance of N. pachyderma. The terrigenous input of the Colombian Pacific rivers, particularly the San Juan River, is suggested as a possible mechanism. Finally, the Globorotalia cultrata/Neogloboquadrina dutertrei ratio is used to reconstruct the past influence of the Costa Rica Dome-Panama Bight and cold tongue upwelling systems in the Panama Basin. A northern influence is suggested for the late Holocene (after 5 ka) and the last glacial (before 20 ka), whereas a southern influence is suggested for the 20-5 ka interval. There is a correspondence between our reconstructed northern and southern influences and previously proposed positions of the Intertropical Convergence Zone (ITCZ) after the Last Glacial Maximum (LGM). © 2005 Elsevier B.V. All rights reserved.Ítem Foraminíferos de las formaciones Jimol y Castilletes (Cuenca de Cocinetas, Alta Guajira): taxonomía y significado paleoambiental(Universidad EAFIT, 2015) Delgado Sierra, Daniel; Martínez Rodríguez, José IgnacioSe determinó la sistemática paleontológica de 39 especies de foraminíferos bentónicos y 12 especies de foraminíferos planctónicos, encontrados en las Formaciones Jimol y Castilletes (Mioceno Temprano-Medio) de la Cuenca de Cocinetas en la Alta Guajira colombiana -- A partir de estas se identificaron, por medio de un análisis de agrupamiento, 14 asociaciones de foraminíferos a través de las unidades geológicas estudiadas. La microfauna planctónica encontrada se usó para datar las unidades en el Burdigaliano y en el Langhiano -- Para interpretar paleoambientalmente los datos: primero se compararon las asociaciones fósiles halladas con comunidades de foraminíferos de ambientes actuales del sur del Mar Caribe (Isla de Barú, Colombia) con el fin de encontrar análogos modernos -- Posteriormente, la morfología del genero bentónico Ammonia fue usada como paleoindicador de condiciones de paleosalinidad, mostrando que esta metodología es promisoria como herramienta para inferir ambientes salobres y distancia con respecto a la costa -- Por último, para cada asociación descubierta fue definido el número de géneros y especies, el índice de diversidad Alpha, la dominancia, el FoRAM Index, el Foraminiferal number, la proporción entre fauna infaunal/epifaunal, planctónica/bentónica y el género planctónico dominante en las muestras con recobro de fauna de este tipo -- Por medio de una síntesis de los resultados obtenidos a partir de las metodologías usadas se reconstruyeron, para la Formación Jimol, condiciones marinas marginales en su sección media que pasan a ambientes de plataforma, para luego volver a entornos proximales -- En la parte superior solo fueron encontradas muestras estériles -- Para la parte baja de la Formación Castilletes fueron sugeridas condiciones marinas marginales que pasan a ambientes de plataforma interna profunda, que luego en la sección media pasan nuevamente a condiciones marinas marginales -- En la parte superior no se encontraron muestras con recobro de microfauna -- La evidencia microfaunal de ambientes deltaicos apoya inferencias previas de condiciones más húmedas durante el Mioceno temprano-medio en la Cuenca de Cocinetas -- Paralelamente, para este mismo periodo de tiempo se sugieren periodos de surgencia oceánica a partir de la fauna planctónica encontrada. Finalmente se propone que existen superficies de inundación análogas a las presentes en las Formaciones Jimol y Castilletes en las Formaciones La Rosa y Querales de VenezuelaÍtem Late Holocene marine terraces of the Cartagena region, southern Caribbean: The product of neotectonism or a former high stand in sea-level?(PERGAMON-ELSEVIER SCIENCE LTD, 2010-03-01) Ignacio Martinez, J.; Yokoyama, Yusuke; Gomez, Andres; Delgado, Adriana; Matsuzaki, Hiroyuki; Rendon, Esteban; Universidad EAFIT. Departamento de Geología; Ciencias del MarThe detailed stratigraphic survey and paleontological study (mollusks, corals, foraminifera and ostracods) of four low-level, ~3 m, marine terrace sections: Punta Canoas, Manzanillo del Mar, Playa de Oro, and Tierra Bomba Island, from the Cartagena region, southern Caribbean, supplemented with 22 radiocarbon dates, reveals that the northern terraces were deposited as parasequences in a clastic depositional system compared to the Tierra Bomba Island succession that was deposited in a carbonate depositional system between ~3600 and ~1700 cal yrs BP. Drier conditions and the southern location of the ITCZ at about 3 ka triggered stronger easterly Trades and more dynamic southwestward sediment drift fed by the Magdalena River mouth, thus promoting the formation of sand spits that ultimately isolated the Cienaga de Tesca coastal lagoon from the Caribbean Sea. Our estimates support the hypothesis that the present position of the terraces is the product of neotectonism rather than a higher 3 ka, sea-level. Upheaval of the terraces varies between ~3.8 mmyr-1 at Punta Canoas and ~2.2 mmyr-1 at Tierra Bomba to ~1.5 mmyr-1 at Manzanillo del Mar and Playa de Oro terraces. Our study corroborates previous contentions on the role of mud diapirism and the dynamics of the Dique Fault as late Holocene upheaval mechanisms. © 2009 Elsevier Ltd. All rights reserved.Ítem Palaeoceanography of the last glacial maximum in the eastern Indian Ocean: Planktonic foraminiferal evidence(ELSEVIER SCIENCE BV, 1999-01-01) Martínez, J.I.; De Deckker, P.; Barrows, T.T.; Universidad EAFIT. Departamento de Geología; Ciencias del MarPalaeoceanographic conditions in the eastern Indian Ocean for the last ~30 kyr are documented by means of planktonic foraminiferal analyses of 10 gravity cores. Quantitative foraminiferal analysis (%), Q-mode factor analysis, the modern analog technique (MAT) and oxygen-isotope analyses are used. A conspicuous increase during the last glacial maximum (LGM) of foraminiferal fragmentation resulting from a more productive Java upwelling system and/or a more corrosive Antarctic Intermediate Water (AAIW) was found at intermediate water depths (~1000 m). Contrasting Q-mode factors based on foraminifera between today and the LGM suggest changes in the thermocline depth, sea-surface temperature (SST), upwelling, and the strength of both the Australasian Mediterranean Water (AAMW) and the Indian Central Water (ICW). The decrease in the percentage abundance of shallow-dwelling and symbiont-bearing planktonic foraminifera, the increase in percentage of the upwelling-related species Globorotalia cultrata and Neogloboquadrina dutertrei, and factor 3 (dominated by Globorotalia tumida and Globigerinella siphonifera) suggest a stronger Java upwelling system during the LGM. A steeper, steric latitudinal gradient (in the presence of a weak Leeuwin Current), and a geostrophic flow similar to today's is postulated for the LGM, and this must have prevented upwelling offshore Western Australia. Today's AAMW-ICW sharp front was weaker during the LGM when the AAMW was saltier, cooler, and nutrient richer and more similar to the ICW. During the LGM, a more gentle SST latitudinal gradient over the ~16 to ~23°S region contrasts with today's steeper conditions at the AAMW-ICW Front. Also, for the LGM, a nutrient-rich ICW may explain previously documented increases in mass accumulation rates of CaCO3, organic carbon and benthonic foraminifera in a region where the nutricline was deep and within the lower euphotic zone.Ítem Paleoceanographic conditions in the western Caribbean Sea for the last 560 kyr as inferred from planktonic foraminifera(ELSEVIER SCIENCE BV, 2007-09-14) Martinez, J. Ignacio; Mora, German; Barrows, Timothy T.; Universidad EAFIT. Departamento de Geología; Ciencias del MarFaunal analyses of planktonic foraminifera and upper-water temperature reconstructions with the modern analog technique are studied and compared to the magnetic susceptibility and gamma ray logs of ODP Core 999A (western Caribbean) for the past 560 kyr in order to explore changes in paleoceanographic conditions in the western Caribbean Sea. Long-term trends in the percentage abundance of planktonic foraminifera in ODP Core 999A suggest two hydrographic scenarios: before and after 480 ka. High percentage abundances of Neogloboquadrina pachyderma and Globorotalia inflata, low abundances of Globorotalia menardii and Globorotalia truncatulinoides, low diversity, and sea-surface temperatures (SST) under 24 °C are typical characteristics occurring from 480 to 560 ka. These characteristics suggest a "shallow" well-oxygenated upper thermocline and the influx of nutrients by either seasonal upwelling plumes and/or eddy-mediated entrainment. The second scenario occurred after 480 ka, and it is characterized by high and fluctuating percentage abundances of Neogloboquadrina dutertrei, G. truncatulinoides, G. menardii, Globigerinita glutinata, Globigerinella siphonifera, and Globigerinoides ruber; a declining trend in diversity; and large SSTs. These characteristics suggest a steady change from conditions characterized by a "shallow" thermocline and chlorophyll maximum to conditions characterized by a "deep" thermocline (mainly during glacial stages) and by more oligotrophic conditions. The influence of the subtropical North Atlantic on the upper thermocline was apparently larger during glacial stages, thus favoring a deepening of the thermocline, an increase in sea-surface salinity, and a dramatic reduction of nutrients in the Guajira upwelling system. During interglacial stages, the influx of nutrients from the Magdalena River is stronger, thus resulting in a deep chlorophyll maximum and a fresher upper ocean. The eddy entrainment of nutrients is the probable mechanism responsible of transport from the Guajira upwelling and Magdalena River plumes into ODP 999A site. © 2007 Elsevier B.V. All rights reserved.Ítem The paleoecology of Late Cretaceous upwelling events from the upper Magdalena basin, Colombia(SEPM-SOC SEDIMENTARY GEOLOGY, 2003-10-01) Martinez, JI; Universidad EAFIT. Departamento de Geología; Ciencias del MarTen planktonic foraminiferal zones are identified and six stratigraphic sequences are interpreted in the Turonian-Maastrichtian interval of the Michu-1 well in the Upper Magdalena Basin. Anoxic bottom-water conditions prevailed during the Turonian and Coniacian followed by dysoxic conditions in the Santonian and Campanian. Oxic conditions were established during the Maastrichtian age. Upwelling occurred for most of the Late Cretaceous. Coccolithophorids, planktonic foraminifera, radialaria, ammonites, clupeoid fish, and mosasaurs dominated the food-web structure of the Turonian-Coniacian interval. Following a major turnover during the Coniacian-Santonian boundary interval, dinoflagellates were the primary producers that sustained radiolarians, a sparse population of planktonic foraminifera, clupeoid fish, and ammonites. Dinaflagellate blooms (peridinoids) were frequent during the Campanian interval and sustained a sparse population of planktonic foraminifera and abundant clupeoid fish whose feces (phosphatic pellets) were grazed extensively by a specialized population of buliminids dominated by the genus Siphogenerinoides.Ítem Paleoenvironmental reconstruction for the lower Pliocene Arroyo Piedras section (Tubará - Colombia): Implications for the Magdalena River - paleodelta's dynamic(PERGAMON-ELSEVIER SCIENCE LTD, 2012-11-01) Molinares, C. E.; Martinez, J. I.; Fiorini, F.; Escobar, J.; Jaramillo, C.; Universidad EAFIT. Departamento de Geología; Ciencias del MarThe Magdalena river transports one of the largest load of sediments per basin area in the world. Its delta position has changed several times over the Neogene. The Arroyo Piedras Section (169 m) in northern Colombia, contains part of the record of the Late Miocene to Early Pliocene evolution of the Magdalena paleodelta. The section was described and sampled for sedimentological and micropaleontological analyses. Based on lithofacies and benthic foraminifera content, the section was divided in three segments, and the upper segment was dated as Early Pliocene using planktonic foraminifera. The lower segment suggests siliciclastic sedimentation in a proximal prodelta/delta plain transitional environment. The intermediate segment suggests sedimentation in a lagoon and/or coastal swamp environment, whereas the upper segment is interpreted as the result of a transgression and subsequent deposition at the foreshore/upper shoreface environment, with a considerable decrease of terrigenous input. The decrease of sediment delivery to the delta produced by permanent El Niño-like conditions coupled with autocyclic processes could explain the transgressive pattern observed in the Arroyo de Piedras section during the Early Pliocene. © 2012 Elsevier Ltd.Ítem Paleoenvironmental reconstruction for the lower Pliocene Arroyo Piedras section (Tubará e Colombia): Implications for the Magdalena River e paleodelta’s dynamic(Elsevier, 2012-04-02) Molinares, C.E.; Martinez, J.I.; Fiorini c, F.; Escobard, J.; Jaramillo, C.; Universidad EAFIT. Departamento de Geología; José Ignacio Martínez (jimartin@eafit.edu.co); Ciencias del MarThe Magdalena river transports one of the largest load of sediments per basin area in the world. Its delta position has changed several times over the Neogene. The Arroyo Piedras Section (169 m) in northern Colombia, contains part of the record of the Late Miocene to Early Pliocene evolution of the Magdalena paleodelta. The section was described and sampled for sedimentological and micropaleontological analyses. Based on lithofacies and benthic foraminifera content, the section was divided in three segments, and the upper segment was dated as Early Pliocene using planktonic foraminifera. The lower segment suggests siliciclastic sedimentation in a proximal prodelta/delta plain transitional environment. The intermediate segment suggests sedimentation in a lagoon and/or coastal swamp environment, whereas the upper segment is interpreted as the result of a transgression and subsequent deposition at the foreshore/upper shoreface environment, with a considerable decrease of terrigenous input. The decrease of sediment delivery to the delta produced by permanent El Niño-like conditions coupled with autocyclic processes could explain the transgressive pattern observed in the Arroyo de Piedras section during the Early PlioceneÍtem Quantitative biostratigraphic model for the tertiary of the lower Magdalena Basin, Colombian Caribbean(Ecopetrol, 2006-01-01) Cuartas, C.; Jaramillo, C.; Martínez, J.-I.; Universidad EAFIT. Departamento de Geología; Ciencias del MarThe reinterpretation of biostratigraphic information by new models and quantitative correlation techniques substantially improves its resolution and its correlative potential, thus minimizing oil exploration risks. With this aim, biostratigraphic information, i.e. first (FO) and last (LO) occurrence events of benthonic and planktonic foraminifera was analysed from sixteen wells from the Lower Magdalena Valley (LMV). The inconsistencies found in the biostratigraphic record, i.e. varying successions of first and last appearances of species from well to well as a result of several factors such incomplete sampling and preservation, true variation in the distribution of fosil taxa, etc., and the great amount of biostratigraphic data makes it practically impossible to accurately constrain basin history from biostratigraphic information by unaided visual inspection. This motivates the treatment of biostratigraphic information with new quantitative approaches, such as constrained optimization (CONOP9 software) and graphic correlation concepts (GraphCor 3,0) and the comparative method approach of Cooper et al. (2001). The succession of biostratigraphic events found through the application of each technique was statistically filtered and compared with Kendall tau coefficients whose values were 0,8. An optimal biostratigraphic succession of LOs was found and calibrated with the Berggren et al. (1995) global time scale by a LOESS regression model for the middle Eocene-Pliocene interval, thus revealing three major changes in sediment accumulation rates for the basin during this time interval: (1) middle Eocene to Oligocene, with low accumulation rates, (2) early Miocene to middle Miocene, with high accumulation rates and (3) late Miocene to Pliocene, with lower accumulation rates. The calibrated composite succession enabled the construction of age-well depth plots, which indicate periods of local deposition and accumulation rates, and periods of erosion, no deposition or very low accumulation rates (unconformities). The best plots were used to build a model for the correlation of unconformities, which shows that they are heterochronous, lasted at least 2,5 Ma, and are of limited extent. Finally, a correlation model was proposed that includes: (1) a time-calibrated succession of biostratigraphic events, and (2) a Haq curve that shows how each geologic period is recorded in each well.Ítem Southwest Pacific Ocean response to a warmer world: Insights from marine isotope stage 5e(AMER GEOPHYSICAL UNION, 2013-09-01) Cortese, G.; Dunbar, G. B.; Carter, L.; Scott, G.; Bostock, H.; Bowen, M.; Crundwell, M.; Hayward, B. W.; Howard, W.; Martinez, J. I.; Moy, A.; Neil, H.; Sabaa, A.; Sturm, A.; Universidad EAFIT. Departamento de Geología; Ciencias del MarPaleoceanographic archives derived from 17 marine sediment cores reconstruct the response of the Southwest Pacific Ocean to the peak interglacial, Marine Isotope Stage (MIS) 5e (ca. 125 ka). Paleo-Sea Surface Temperature (SST) estimates were obtained from the Random Forest model - an ensemble decision tree tool - applied to core-top planktonic foraminiferal faunas calibrated to modern SSTs. The reconstructed geographic pattern of the SST anomaly (maximum SST between 120 and 132 ka minus mean modern SST) seems to indicate how MIS 5e conditions were generally warmer in the Southwest Pacific, especially in the western Tasman Sea where a strengthened East Australian Current (EAC) likely extended subtropical influence to ca. 45°S off Tasmania. In contrast, the eastern Tasman Sea may have had a modest cooling except around 45°S. The observed pattern resembles that developing under the present warming trend in the region. An increase in wind stress curl over the modern South Pacific is hypothesized to have spun-up the South Pacific Subtropical Gyre, with concurrent increase in subtropical flow in the western boundary currents that include the EAC. However, warmer temperatures along the Subtropical Front and Campbell Plateau to the south suggest that the relative influence of the boundary inflows to eastern New Zealand may have differed in MIS 5e, and these currents may have followed different paths compared to today. Key Points Oceanic conditions at 125 kyr seem to agree with recent observations/trendsEast Australian Current probably stronger and Tasman Front cooler during MIS 5eObserved oceanographic changes likely linked to increases in wind stress curl ©2013. American Geophysical Union. All Rights Reserved.