Cretaceous to Middle Cenozoic Exhumation History of the Cordillera de Domeyko and Salar de Atacama Basin, Northern Chile

Spatiotemporal patterns of deformation and exhumation in the central Andes are key parameters for reconstructing the kinematic history of the orogenic belt. Previous studies of the retroarc thrust belt document overall eastward propagation of deformation since the late Eocene, but the amount and timing of exhumation during the early phase of Andean orogeny remains largely unconstrained, particularly in the modern forearc region. In order to determine the timing and amount of exhumation prior to the late Eocene, we employed a multidating approach combining zircon U-Pb geochronology with apatite fission track and apatite (U-Th)/He thermochronology. We focus on the low-temperature cooling history of the Cordillera de Domeyko thrust belt and synorogenic deposits in the Salar de Atacama basin. Our results show Late Cretaceous to Oligocene cooling and exhumation in the Cordillera de Domeyko. The distribution of cooling ages in the forearc indicates three periods of exhumation: 86-65, 65-50, and 50-28Ma. The amount of cooling was variable in space and time but requires total exhumation of 2.5-3.3km of rocks above major structures in the thrust belt. Regional unconformities in the Salar de Atacama basin correlate with periods of eastward migration of the orogenic front at 65Ma and 50-40Ma. Pulses of deformation at the front of the thrust belt alternated with periods of out-of-sequence hinterland deformation and exhumation. Overall, our data show that shortening in the central Andes commenced during the Late Cretaceous (as early as 86Ma) and that deformation (shortening) and exhumation were coupled in space and time.GSA Research Grant; U.S. National Science Foundation-Tectonics Program [EAR-071069]6 month embargo; published online: 26 December 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Cretaceous 40 Ar/ 39 Ar detrital mica ages in Tertiary sediments shed a new light on the Eo-Alpine evolution

Clastic sediments deposited in the syn-orogenic Tertiary Piedmont Basin in northwest Italy represent the depositional counterpart of the cooling/exhumation and erosion of Western Alpine rocks over the last 30- 35 Myr. 40 Ar/ 39 Ar analyses of detrital white micas from Oligocene-Miocene sediments and present-day river sands show, in addition to younger Tertiary age groups, a wide range of Cretaceous ages. Pronounced well defined Late Cretaceous (~70-90 Ma) and Early Cretaceous (~105-120 Ma) age clusters are recorded in Lower to Upper Miocene sediments, forming discrete age groups with a contribution to the total detrital population of as high as 58%. This age pattern of discrete age peaks is remarkably constant and can be followed up-sequence through different formations spanning a time interval for sedimentation of >20 Myr. Our new detrital mica ages may be the result of either excess Ar in the source rock, as commonly assumed for HP mica Ar ages from the internal western Alps, or of inherited Ar, and consequently be representative of real geological events. The first scenario would imply that incorporation of excess Ar in minerals can lead to non-random detrital age populations which could then mistakenly be interpreted as representative of real geological events. The second scenario would imply that during the last Eocene thermal event, pre-existing micas were only partially overprinted and the presence of older ages are the result of real Cretaceous metamorphic events of the Western Alpine orogen. We argue that our new data derived from the sedimentary record, in particular from the time interval from Serravallian to Present, cannot easily be explained as simply being due to incorporation of excess argon. We therefore interpret these ages to be representative of cooling following major metamorphic events in the Alpine orogen. The new argon data from the sediments in combination with the data from the rocks exposed in the orogen today point to a complex Mesozoic history of the internal Alpine orogen

Effects of Miocene–Pliocene global climate changes on continental sedimentation: A case study from the southern Central Andes

Sedimentation rates are valuable proxies for changes in tectonics, climate, and sediment routing systems. We use sedimentation rates from the Bermejo foreland basin of the southern Central Andes to evaluate the role of global Miocene-Pliocene climate changes on continental erosion and sedimentation in non-glaciated landscapes. Our compilation identifies a tripling of sedimentation rates between ca. 10 and 8.5 Ma coinciding with a period of short-lived global warming and increased seasonality, and a decrease by half in sedimentation rates between ca. 6 and 5 Ma coinciding with increased global cooling and aridity. Both the increase and decrease in sedimentation rates occured during periods of heightened tectonic activity. Our results suggest that periods of aridity can reduce erosion and mask contemporaneous tectonic signals, and that more humid, variable climate conditions amplify the signal of tectonic forcing in the sedimentary record. This work shows that changes in sedimentation rates can accurately filter climatic variabilities out of the overprinting tectonic signal.National Science Foundation Graduate Research Fellowship; National Geographic Young Explorer's grant [9744-15]; Geological Society of America Graduate Student Research grant12 month embargo; published online: 7 June 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Using basin thermal history to evaluate the role of Miocene-Pliocene flat-slab subduction in the southern Central Andes (27 degrees S-30 degrees S)

Studies in both modern and ancient Cordilleran-type orogenic systems suggest that processes associated with flat-slab subduction control the geological and thermal history of the upper plate; however, these effects prove difficult to deconvolve from processes associated with normal subduction in an active orogenic system. We present new geochronological and thermochronological data from four depositional areas in the western Sierras Pampeanas above the Central Andean flat-slab subduction zone between 27 degrees S and 30 degrees S evaluating the spatial and temporal thermal conditions of the Miocene-Pliocene foreland basin. Our results show that a relatively high late Miocene-early Pliocene geothermal gradient of 25-35 degrees C km(-1) was typical of this region. The absence of along-strike geothermal heterogeneities, as would be expected in the case of migrating flat-slab subduction, suggests that either the response of the upper plate to refrigeration may be delayed by several millions of years or that subduction occurred normally throughout this region through the late Miocene. Exhumation of the foreland basin occurred nearly synchronously along strike from 27 to 30 degrees S between ca. 7 Ma and 4 Ma. We propose that coincident flat-slab subduction facilitated this widespread exhumation event. Flexural modelling coupled with geohistory analysis show that dynamic subsidence and/or uplift associated with flat-slab subduction is not required to explain the unique deep and narrow geometry of the foreland basin in the region implying that dynamic processes were a minor component in the creation of accommodation space during Miocene-Pliocene deposition.NSF GRF, National Geographic Young Explorer's Grant [9744-15]; GSA Graduate Student Research Grant12 month embargo; published online: 01 September 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Os canais de feedback no departamento de Acolhimento e Comercialização da Associação de Turismo do Porto e Norte: o perfil do cliente do back office

Relatório de estágioNas últimas décadas, o setor do turismo foi marcado por um crescimento exponencial progressivo que veio consolidar a sua posicao no mundo como um dos setores mais importantes. A cidade do Porto, seguindo a tendência do país, Portugal, vive agora também anos de crescimento significativo para o setor. O seu centro historico foi classificado como Patrimonio da Humanidade pela UNESCO e em 2012, 2014 e 2017 recebeu o titulo de Melhor Destino Europeu. No entanto, com o aumento da procura, surgem também responsabilidades acrescidas para as entidades que gerem, regulam e coordenam o destino turístico, nomeadamente as Destination Management Organizations (DMO's). Como principais fontes de informação, assumem relevante importância, pois serão uma ponte essencial de contacto, recolha de informacao e esclarecimento de duvidas entre o destino e os potenciais turistas, mas também turistas já no destino. Objetivo - O objetivo principal deste estudo, realizado em ambiente de estagio curricular, e' compreender quais os canais de feedback existentes em ambiente de back office, no departamento de Acolhimento e Comercialização da Associaçao de Turismo do Porto, AR. - Porto Convention & Visitors Bureau. Para alem disso, será também objetivo deste relatorio compreender o comportamento da procura mediante cada canal de entrada. Metodologia - Para responder aos objetivos deste estudo, foram criadas duas possiveis análises - uma das vendas realizadas em back office, no ano de 2018, e outra relativa aos pedidos de informação via ferramenta LiveChat, entre novembro de 2018 e marco de 2019 (periodo de estágio). Foram aferidos 338 contactos que resultaram em vendas em back office (provenientes de 11 canais de feedback) e 4196 conversas iniciadas na ferramenta live presente nos Websites Visit Porto e Visit Porto and North. Resultados - Os dados recolhidos confirmam que os turistas priorizam três principais canais de feedback - o Chat, o Email - visitportoandnorth e o Telefone. Os canais Chat e Telefone sao principalmente utilizados por famílias e grupos de amigos, que procuram a realizaçao de cruzeiros, com estadias curtas e reservam com pouca antecedência, no mesmo mês da visita ou apenas no mês anterior. Por outro lado, o canal Email - visitportoandnorth, principalmente priorizado para visitas mais profissionais e de negocios, é utilizado por agências de viagens/operadores turisticos/similares, empresas e escolas, que prezam a antecedência e investem nos circuitos organizados e a medida, como forma de conhecer a cidade. Limitações e Implicações - O período temporal escolhido para o estudo não permite que os dados recolhidos sejam generalizados. A falta de estudos semelhantes na entidade em estudo levou à maior utilização do tempo na aferição das categorias possiveis de recolher informações, o que limitou o periodo associado a problematização e cruzamento critico das informações recolhidas e possíveis conclusões mais especificas. Implicações práticas - Este estudo pretende demonstrar a importância da analise da procura para as entidades que gerem os destinos, como forma de afinar e melhor direcionar a sua atuação, tendo em conta as diferenças dos mercados. Originalidade/Valor - São ainda escassos os estudos, na entidade, que analisam ao pormenor a procura via back office. Existe a necessidade de explorar a forma como a procura não presencial atua nas entidades gestoras dos destinos turísticos, principalmente pela crescente adesão ao online.Over the last decades, the tourism sector has seen progressive exponential growth, consolidating its position in the world as one of the most important sectors. Porto, following the country”s trend, Portugal, now lives also years of significant growth for the sector. lts historic center has been classified as a World Heritage Site by UNESCO and in 2012, 2014 and 2017, the city received the Best European Destination's award. However, as demand increases, responsibilities are also added to the entities that manage, regulate and coordinate the tourism destination, namely Destination Management Organizations (DMO's). As main information sources” with high importance, the Dl\/lOs should not be forgotten. They are an essential bridge of contact, gathering information and clarifying doubts between the destination and potential demand, but also for tourists already at the destination. Objective - The main objective of this study, carried out in a curricular internship environment, is to understand which feedback channels exist in a back-office environment, in the “Hospitality and commercialization” department of the Porto Tourism Association, A.R. - Porto Convention & Visitors Bureau. ln addition, it will also be objective to understand how demand behaves through each input channel. Methodology - ln order to meet the objectives of this study, two possible analysis were created - one concerning the back-office sales of 2018, and the other related to requests for information via LiveChat tool, between November 2018 and March 2019 (internship period). 338 contacts were verified which resulted in backzoffice sales (from 11 feedback channels) and 4196 conversations started in the live tool existing on the Visit Porto and Visit Porto and North websites. Results - The data collected confirm that tourists prioritize three main feedback channels - Chat, Email - visitportoandnorth and Telephone. Chat and Telephone channels are mainly used by families and groups of friends, who mainly search for cruises, prefer short stays and book shortly in advance, in the same month of the visit or just the previous month. On the other hand, the Email - visitportoandnorth channel, mainly prioritized for more professional and business visits, is used by travel agencies/tour operators/similar, companies and schools, who value the advance and invest in organized and tailored circuits to know the city. Limitations and implications - The time period chosen for study does not allow the collected data to be generalized. The lack of similar studies in the study entity led to the greater use of time in assessing the categories possible to collect information, which restricted the time affecting the discussion and critical crossing of the collected information and perhaps more specific conclusions. Practical implications - This study aims to demonstrate the importance of demand analysis for destination management entities as a way of fineztuning and better targeting, considering market differences. Originality/value - There are still few studies in the entity that analyze in detail the demand via back-office. There is a need to explore the way non-presential demand acts in tourism destination management entities, mainly due to the growing use of online tools

Faulting and erosion in the Argentine Precordillera during changes in subduction regime: Reconciling bedrock cooling and detrital records

The Argentine Precordillera is an archetypal retroarc fold-and-thrust belt that records tectonics associated with changing subduction regimes. The interactions between exhumation and faulting in the Precordillera were investigated using apatite and zircon (U–Th–Sm)/He and apatite fission track thermochronometry from the Precordillera and adjacent geologic domains. Inverse modeling of thermal histories constrains eastward in-sequence rock cooling associated with deformation and erosion from 18 to 2 Ma across the Central Precordillera tracking thrusting during this time. The youngest AHe ages (5–2 Ma) and highest erosion rates are located in the eastern and western extremities of the Precordillera and indicate that recent denudation is concentrated at its structural boundaries. Moreover, synchronous rapid Pliocene cooling of the Frontal Cordillera, Eastern Precordillera, and Sierra del Valle Fértil was coeval with initiation of basement-involved faulting in the foreland. Detrital zircon U–Pb geochronology from the ca. 16–8.1 Ma Bermejo foreland basin strata suggests fluvial connectivity westward beyond the Frontal Cordillera to the Main Cordillera and Coast Range followed by an important shift in sediment provenance at ca. 10 Ma. At this time, we suggest that a substantial decrease in Permo-Triassic igneous sources in the Frontal Cordillera and concurrent increase in recycled zircons signatures of Paleozoic strata are best explained by uplift and erosion of the Precordillera during widening of the thrust-belt. Bedrock thermochronology and modeling indicate a 2–6 Myr lag time between faulting-related cooling in the hinterland and the detrital record of deformation in the foreland basin, suggesting that for tectonically active semi-arid settings, bedrock cooling may be more sensitive to onset of faulting. We suggest that high erosion rates in the Frontal Cordillera and Eastern Precordillera are associated with increased interplate coupling during shallowing of the subducting Nazca plate that may concentrate stress along weak structural boundaries of the Precordillera.Fil: Fosdick, Julie. Indiana University; Estados UnidosFil: Carrapa, Barbara. University of Arizona; Estados UnidosFil: Ortiz, Gustavo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentin

The early stages of the Alpine collision: an image derived from the upper Eocene–lower Oligocene record in the Alps–Apennines junction area

Abstract: The upper Eocene-lower Oligocene sediments deposited in the eastern part of the Tertiary Piedmont Basin in northern Italy provide a complete record of the unroofing of the Alpine orogenic prism during the early stages of exhumation in the Ligurian sector. From late Priabonian till late Rupelian time, the sediments in the study area were derived from two different sources, one characterised by white micas with Si<6.5 pfu and Permian (40)Ar/(39)Ar ages (270 Ma), and the other characterised by white micas with S>7 pfu and Eocene-Oligocene (40)Ar/(39)Ar ages (32-50 Ma). The first source is considered to be indicative of low-pressure metamorphic rocks that covered the HP rocks of the Ligurian Alps, and were completely eroded by Chattian time. From this time on, the study area started to record the first input from western Alpine sources characterised by a larger span of ages with a more frequent Eoalpine signal. Thus, sediments deposited in the eastern part of the Tertiary Piedmont Basin contain the only available evidence of rocks belonging to high crustal levels in the Alpine orogenic prism that were not affected by the Alpine overprint. These data also provide time constraints to the poorly dated first conglomerates deposited in this area. (40)Ar/(39)Ar geochronology reveals a minimum age of 33 +/- 1.4 Ma for the Pianfolco Conglomerates in the type locality, and of 31.4 +/- 3.5 Ma for the Borbera Conglomerates

40Ar/39Ar detrital thermochronology on Eocene-Oligocene sediments of the Alps-Apennines junction area provides insights on the early stages of the Alpine orogenesis.

Body cremated. Ellen J. Moberg - wife.https://stars.library.ucf.edu/cfm-ch-register-vol14/1176/thumbnail.jp