This dissertation is a diachronic settlement and landscape study undertaken from an interpretive archaeology perspective. The outcome of this study has been an interpretation of the settlement and landscape configurations as well as of the sociopolitical organization during the entire prehispanic occupation (ca. 1100 B.C.- A.D. 1532) of the Upper Piura River Valley in the Far North Coast of Perú. Also, the sociopolitical interaction between the local polities of the Upper Piura River Valley and the southern foreign Northern North Coast polities has been assessed. The Far North Coast is not an environmentally "marginal" area as compared to the Northern North Coast. Yet, in terms of its prehispanic cultural development, it often has been characterized as "marginal" or "peripheral". Such characterization is due in part to an overemphasis on the study of Mochica style cultural materials found in the Far North Coast. In particular, the emphasis on analyses of "high quality" Mochica ceramics has led to interpretations that view local Upper Piura River Valley sociopolitical developments from the perspective of the "dominant" Northern North Coast societies in an unbalanced situation disregarding the perspective of the supposedly "weaker, less developed" local societies. In this sense, interpretations drawn from iconographic and stylistic analyses of objects on the one hand, and from landscape analyses on the other, seem like two different versions of the same story. Since the latter is so uncommon and unexplored in Andean archaeology, I chose to apply it in this dissertation. For that purpose I followed two different but complementary paths of interpretation. The first path is an interpretation of the landscape from a dwelling perspective. The goal was to create an analogy of the experience of past individuals through an embodiment process via the movement of my body and mind through the landscape features. A second path of interpretation was merged with the first one. This second path comprised a classic settlement pattern analysis oriented to clarify the nature of the sociopolitical interaction between local polities of the Upper Piura River Valley and the intrusive polities of the Northern North Coast. The second path of interpretation also entailed overlapping the settlement patterns observed onto the spatial structures and topograms defined and interpreted by the dwelling perspective. As a result, I found that the study area is characterized by a 2600-year long process of dwelling in the landscape. Through this process and along the years, yet following a long, local process, revolving around the topograms, the landscapes conceptualizations and configurations changed. Two moments of the settlements and landscapes configurations were defined: the "old system" and the "new system". For most of its history (through all the "old system" and the first epoch of the "new system"), and acknowledging the mutual cultural influence with other areas (e.g., the Northern North Coast), the local landscape and settlement configurations were not disrupted and engaged in an egalitarian or coevolving sociopolitical interaction. Yet during the second epoch of the "new system", this situation changed drastically when a hierarchical and coercive interaction structure developed during the Chimú and Inca periods.

We present crustal velocities for 29 continuously recording GPS stations from the southern central Andes across the Puna, Eastern Cordillera, and Santa Barbara system for the period between the 27 February 2010 Maule and 1 April 2014 Iquique earthquakes in a South American frame. The velocity field exhibits a systematic decrease in magnitude from similar to 35mm/yr near the trench to <1mm/yr within the craton. We forward model loading on the Nazca-South America (NZ-SA) subduction interface using back slip on elastic dislocations to approximate a fully locked interface from 10 to 50km depth. We generate an ensemble of models by iterating over the percentage of NZ-SA convergence accommodated at the subduction interface. Velocity residuals calculated for each model demonstrate that locking on the NZ-SA interface is insufficient to reproduce the observed velocities. We model deformation associated with a back-arc decollement using an edge dislocation, estimating model parameters from the velocity residuals for each forward model of the subduction interface ensemble using a Bayesian approach. We realize our best fit to the thrust-perpendicular velocity field with 705% of NZ-SA convergence accommodated at the subduction interface and a slip rate of 9.10.9mm/yr on the fold-thrust belt decollement. We also estimate a locking depth of 149km, which places the downdip extent of the locked zone 13520km from the thrust front. The thrust-parallel component of velocity is fit by a constant shear strain rate of -19x10(-9)yr-(1), equivalent to clockwise rigid block rotation of the back arc at a rate of 1.1 degrees/Myr.

No description available.

The American Cordillera, a major mountain belt spanning>15000 km along the western margins of North and South America, formed as a result of crustal shortening and magmatism during ocean-continent convergence. These mountains were the loci of addition and redistribution of continental crust. The contributions presented here address the style, timing, and kinematics of underthrusting of continental crust in the retroarc of the central Andes as well as the rapid burial and metamorphism of forearc rocks that contributed to magmatism in the Canadian Cordillera. This work involved geological mapping and structural analysis coupled with geo- and thermochronological analysis. In the central Andes, results confirm a southward transition in structural style and magnitude of Cenozoic shortening that coincides with the disappearance of a thick Paleozoic basin that accommodated major Cenozoic shortening. U-Pb and (U-Th)/He results also demonstrate that thrust belt kinematics in northwestern Argentina were greatly influenced by pre-orogenic heterogeneities in Cretaceous rift architecture. Results from western Canada reveal that rapid underthrusting of forearc rocks occurred during Late Cretaceous time, likely associated with an episode of shallow subduction. This event did not result in basement-involved foreland uplifts thought to be a signature of shallow subduction in the western United States and central Argentina. Taken together, this work has the major implication that variations in the pre-orogenic upper crustal architecture strongly influence the behavior of the continental lithosphere during orogenesis, a result that challenges geodynamic models that largely neglect upper plate heterogeneities.

Tectonic development of the Andean Cordillera has profoundly changed the topography, climate, and vegetation patterns of the southern central Andes. The Cenozoic Bermejo Basin in Argentina (30 degrees S) provides a key record of thrust belt kinematics and paleoclimate south of the high-elevation Puna Plateau. Ongoing debate regarding the timing of initiation of upper plate shortening and Andean uplift persists, precluding a thorough understanding of the earlier tectonic and climatic controls on basin evolution. We present new sedimentology, detrital geochronology, sandstone petrography, and subsidence analysis from the Bermejo Basin that reveal siliciclastic-evaporative fluvial and lacustrine environments prior to the main documented phase of Oligocene-Miocene shortening of the Frontal Cordillera and Argentine Precordillera. We report the first radiometric dates from detrital zircons collected in the Cienaga del Rio Huaco Formation, previously mapped as Permian, that constrain a Late Cretaceous (95-93Ma) maximum depositional age. Provenance and paleocurrent data from these strata indicate that detritus was derived from dissected arc and cratonic sources in the north and northeast. Detrital zircon U-Pb ages of 37Ma from the overlying red beds suggest that foredeep sedimentation began by at least the late Eocene. At this time, sediment dispersal shifted from axial southward to transversal eastward from the Andean Arc and Frontal Cordillera. Subsidence analysis of the basin fill is compatible with increasing tectonic deformation beginning in Eocene time, suggesting that a distal foredeep maintained fluvial connectivity to the hinterland during topographic uplift and unroofing of the Frontal Cordillera, prior to Oligocene-Miocene deformation across the Precordillera.

A lingering question in Cordilleran tectonics is how high plateaus form in the absence of continental collision. The type example of an active Cordilleran high plateau is found in the Central Andes of Peru, Bolivia, Argentina, and Chile. Along this section of the South American Cordillera, tectonics are primarily driven by subduction of the oceanic Nazca Plate beneath the continental South American Plate. Extending over 1,800 km along the active continental margin, the Central Andean Plateau (CAP) reaches a maximum width of around 400 km with several peaks in excess of 6 km. Numerous morphotectonic subdivisions of the CAP highlight the complex along-strike variability of the Plateau providing a natural laboratory for investigating the relative contribution of tectonic processes involved in building and maintaining Cordilleran high plateaus. The scale of this problem extends far beyond the scope of any one geoscientific discipline requiring a multidisciplinary approach. Our contribution to this scientific problem and the focus of the work presented in this dissertation is to better understand the current lithospheric and uppermost mantle structure along the CAP. This is achieved by integrating recent advances in seismic imaging techniques with a growing availability of high-quality seismic data into three distinct studies across the South American continent. In the first study, we present a shear-wave velocity model for the crust below the Altiplano-Puna Volcanic Complex (APVC). The target of this study is to constrain the crustal volume of a large magma reservoir inferred to exist below the APVC. When combined with geological and petrological constraints, the large-volume magma reservoir imaged in this study suggests a significant magmatic contribution to the growth of the Plateau in excess of one kilometer over the last ten million years. In addition to the tectonic contributions of this work, we introduce a new method of jointly inverting surface-wave dispersion data and receiver functions to generate a three-dimensional velocity model. In the second study, we combine Rayleigh-wave dispersion data from ambient noise and earthquake-generated surface waves to invert for a shear-wave velocity model of the lithosphere and uppermost mantle below the Bolivian Orocline. The target of this study is to identify any possible mantle contributions to the uplift history along the northern CAP. The highlight of this study is a high-velocity feature that extends from the base of the crust to ~120 km depth below the Altiplano basin. We interpret this feature using a simple isostatic model and suggest it is responsible for the relatively low topography of the Altiplano basin. In the third and final study, we extend the seismic model of the APVC crust to cover the entire Puna Plateau (southern CAP). The target of this study is to assess the uniqueness of the APMB and to look for additional magma reservoirs in the crust. A highlight of this work is the nearly one-to-one spatial correlation between the long-wavelength topography, ignimbrite deposits, long-wavelength Bouguer gravity anomalies, and four additional mid-crustal low-velocity zones imaged in the southern Puna Plateau. When placed in the context of existing geological and petrological constraints, we suggest the contribution of magmatic addition as an uplift mechanism in Cordilleran systems is much larger than is currently accepted.

Entre 12 e 4Ma, intensas manifestações vulcânicas explosivas ocorrem associadas a formação de grandes caldeiras no platô dos Andes Centrais, lançando mais de 10.000 km3 de material piroclástico e constituindo o Complexo Vulcânico Altiplano Puna (CVAP). O Cerro Pululus, com aproximadamente 178 km2 e 550 m de altura, é uma colina em forma de escudo constituída por três unidades de fluxo ignimbrítico lançadas por um mesmo centro emissor durante os eventos do CVAP. No cume do cerro aflora um corpo intrusivo sub-vulcânico que elevou e deformou os depósitos piroclásticos na forma de um anticlinal. Pululus está localizado na borda sul da Caldeira Vilama, uma das maiores estruturas de colapso do CVAP, que teria sido responsável pela deposição de mais de 1.200 km3 de material piroclástico. O local de emissão dos ignimbritos de Pululus ainda é desconhecido e sua relação com os depósitos da Caldeira Vilama é considerada incerta. A alta concentração de cristais nos púmices evidencia que os depósitos do Cerro Pululus foram originados por um magma porfirítico, apresentando plagioclásio, biotita, quartzo, ferrossilita, enstatita, augita e hornblenda, como minerais principais. As unidades são de composição dacítica e pertencem à série cálcio-alcalina de alto-K, com características meta a peraluminosas e razões A/CNK variando entre 0,9 e 1,04. As feições texturais dos minerais (e.g. texturas de dissolução no plagioclásio) e os dados químicos obtidos (e.g. presença de dois tipos de púmices) evidenciam recorrentes injeções máficas na câmara magmática. A alta taxa de cristalinidade da fusão (50 a 68%) tornou desfavorável o processo de fracionamento e reduziu a ação de correntes de convecção na câmara, evitando a homogeneização do magma. A presença de bordas de reação nos anfibólios, somada a outras evidências observadas no afloramento, indicam que durante o início do evento eruptivo o magma ascendeu a uma velocidade consideravelmente baixa, permitindo a liberação de uma grande quantidade de voláteis e resultando numa erupção de caráter mais explosivo. Com a abertura do sistema e o abatimento da pressão dentro da câmara, ocorre a aceleração na cristalização do fundido, resultando no progressivo aumento de saturação de água em algumas porções da câmara e a conseqüente estabilização e cristalização de anfibólio antes da última erupção. A comparação entre os ignimbritos da Caldeira Vilama e Cerro Pululus é feita, neste trabalho, utilizando-se características deposicionais, petrográficas e químicas. Ambos são compostos por três unidades de fluxo que apresentam similaridades quanto à cor, grau de soldamento, relações estratigráficas, quantidade e tipos de púmices, quantidade e tipos de fragmentos líticos, assembléia mineralógica e composição química. Todos esses elementos, além da inexistência de qualquer conduto vulcânico no cerro, permitem estimar que os depósitos de Pululus representem uma extensão do Ignimbrito Vilama. / About 12 and 4Ma, ago intense explosive volcanic manifestations occurred associated to the formation of the large calderas in the Andean Central Volcanic Zone plateau, launching more than 10.000 km3 of ignimbrites and constituting the Altiplano-Puna Volcanic Complex (APVC). The Cerro Pululus, of about 178 km2 and 550 m high, is a shield-like hill constituted by three units of ignimbritic flows originated from same emission center during APVC\'s events. A sub-volcanic intrusive body, that elevated and deformed the pyroclastic deposits in the form of an anticline, crops out at the hill top. Pululus is located in the south ring of the Vilama caldera, one of the largest of the APVC\'s collapse structures, which would have been responsible for the deposition of more than 1.200 km3 of pyroclastic material. The emission center of Pululus ignimbrites is still unknown and its relationship with the deposits of the Vilama caldera is considered uncertain. The high crystal concentration in the pumices evidences that the deposits of Cerro Pululus were originated from a porphyritic magma, with plagioclase, biotite, quartz, ferrosilite, enstatite, augite and hornblend as main minerals. The units are of dacitic composition and belong to the high-K calc-alkaline series, with metaperaluminous characteristics and A/CNK reasons between 0.9 and 1.04. The textural features of the minerals (e.g. dissolution textures in plagioclase) and the obtained chemical data (e.g. presence of two types of pumices) evidence recurring mafic injections in the magmatic chamber. The high cristallinity rate by the melt (50 to 68%) turned unfavorable the fractionation process and reduced the convection currents action in the chamber, hindering the homogenization of the magma. The presence of reaction borders in amphibole, besides some evidences observed in the outcrops, indicate that during the beginning of the eruptive event the magma ascended of a considerably low speed, which allowed the liberation of a great quantity of volatiles and resulted in an eruption of more explosive character. With the opening of the system and the pressure surcease inside the chamber, an acceleration in the crystallization of the melt occurred, resulting in progressive water saturation increase in some portions of the chamber and consequent amphibole stabilization and crystallization before the last eruption. A comparison between ignimbrites of the Vilama caldera and Cerro Pululus is made, in this work, using depositional, petrographics and chemical characteristic. They are both composed by three flow units that present similarities regarding color, welding, stratigraphic relationships, quantity and types of pumices, quantity and types of lithic fragments, mineralogical assembly and chemical composition. All of these elements, besides the inexistence of any volcanic conduit on the hill, allow to correlate the Pululus ignimbrites directly with those of Vilama.

Entre 12 e 4Ma, intensas manifestações vulcânicas explosivas ocorrem associadas a formação de grandes caldeiras no platô dos Andes Centrais, lançando mais de 10.000 km3 de material piroclástico e constituindo o Complexo Vulcânico Altiplano Puna (CVAP). O Cerro Pululus, com aproximadamente 178 km2 e 550 m de altura, é uma colina em forma de escudo constituída por três unidades de fluxo ignimbrítico lançadas por um mesmo centro emissor durante os eventos do CVAP. No cume do cerro aflora um corpo intrusivo sub-vulcânico que elevou e deformou os depósitos piroclásticos na forma de um anticlinal. Pululus está localizado na borda sul da Caldeira Vilama, uma das maiores estruturas de colapso do CVAP, que teria sido responsável pela deposição de mais de 1.200 km3 de material piroclástico. O local de emissão dos ignimbritos de Pululus ainda é desconhecido e sua relação com os depósitos da Caldeira Vilama é considerada incerta. A alta concentração de cristais nos púmices evidencia que os depósitos do Cerro Pululus foram originados por um magma porfirítico, apresentando plagioclásio, biotita, quartzo, ferrossilita, enstatita, augita e hornblenda, como minerais principais. As unidades são de composição dacítica e pertencem à série cálcio-alcalina de alto-K, com características meta a peraluminosas e razões A/CNK variando entre 0,9 e 1,04. As feições texturais dos minerais (e.g. texturas de dissolução no plagioclásio) e os dados químicos obtidos (e.g. presença de dois tipos de púmices) evidenciam recorrentes injeções máficas na câmara magmática. A alta taxa de cristalinidade da fusão (50 a 68%) tornou desfavorável o processo de fracionamento e reduziu a ação de correntes de convecção na câmara, evitando a homogeneização do magma. A presença de bordas de reação nos anfibólios, somada a outras evidências observadas no afloramento, indicam que durante o início do evento eruptivo o magma ascendeu a uma velocidade consideravelmente baixa, permitindo a liberação de uma grande quantidade de voláteis e resultando numa erupção de caráter mais explosivo. Com a abertura do sistema e o abatimento da pressão dentro da câmara, ocorre a aceleração na cristalização do fundido, resultando no progressivo aumento de saturação de água em algumas porções da câmara e a conseqüente estabilização e cristalização de anfibólio antes da última erupção. A comparação entre os ignimbritos da Caldeira Vilama e Cerro Pululus é feita, neste trabalho, utilizando-se características deposicionais, petrográficas e químicas. Ambos são compostos por três unidades de fluxo que apresentam similaridades quanto à cor, grau de soldamento, relações estratigráficas, quantidade e tipos de púmices, quantidade e tipos de fragmentos líticos, assembléia mineralógica e composição química. Todos esses elementos, além da inexistência de qualquer conduto vulcânico no cerro, permitem estimar que os depósitos de Pululus representem uma extensão do Ignimbrito Vilama. / About 12 and 4Ma, ago intense explosive volcanic manifestations occurred associated to the formation of the large calderas in the Andean Central Volcanic Zone plateau, launching more than 10.000 km3 of ignimbrites and constituting the Altiplano-Puna Volcanic Complex (APVC). The Cerro Pululus, of about 178 km2 and 550 m high, is a shield-like hill constituted by three units of ignimbritic flows originated from same emission center during APVC\'s events. A sub-volcanic intrusive body, that elevated and deformed the pyroclastic deposits in the form of an anticline, crops out at the hill top. Pululus is located in the south ring of the Vilama caldera, one of the largest of the APVC\'s collapse structures, which would have been responsible for the deposition of more than 1.200 km3 of pyroclastic material. The emission center of Pululus ignimbrites is still unknown and its relationship with the deposits of the Vilama caldera is considered uncertain. The high crystal concentration in the pumices evidences that the deposits of Cerro Pululus were originated from a porphyritic magma, with plagioclase, biotite, quartz, ferrosilite, enstatite, augite and hornblend as main minerals. The units are of dacitic composition and belong to the high-K calc-alkaline series, with metaperaluminous characteristics and A/CNK reasons between 0.9 and 1.04. The textural features of the minerals (e.g. dissolution textures in plagioclase) and the obtained chemical data (e.g. presence of two types of pumices) evidence recurring mafic injections in the magmatic chamber. The high cristallinity rate by the melt (50 to 68%) turned unfavorable the fractionation process and reduced the convection currents action in the chamber, hindering the homogenization of the magma. The presence of reaction borders in amphibole, besides some evidences observed in the outcrops, indicate that during the beginning of the eruptive event the magma ascended of a considerably low speed, which allowed the liberation of a great quantity of volatiles and resulted in an eruption of more explosive character. With the opening of the system and the pressure surcease inside the chamber, an acceleration in the crystallization of the melt occurred, resulting in progressive water saturation increase in some portions of the chamber and consequent amphibole stabilization and crystallization before the last eruption. A comparison between ignimbrites of the Vilama caldera and Cerro Pululus is made, in this work, using depositional, petrographics and chemical characteristic. They are both composed by three flow units that present similarities regarding color, welding, stratigraphic relationships, quantity and types of pumices, quantity and types of lithic fragments, mineralogical assembly and chemical composition. All of these elements, besides the inexistence of any volcanic conduit on the hill, allow to correlate the Pululus ignimbrites directly with those of Vilama.

This thesis reports a rock slope hazard investigation located in the Central Andes of Chile, where two significant rock mass wasting events were recognized. Dating using cosmogenic nuclide for ³⁶Cl showed that the deposits were post-glacial in age, corresponding to the Upper Pleistocene Portillo Rock Avalanche (PRA) and a Holocene rock slump and rockslide. The pre-historic landslide deposits underlie both a key transportation route between Chile and Argentina and an important ski resort. The purpose of this research was to investigate the likely failure mechanism and characterise the runout path and volume of the PRA. The insights gained on the back analysis of the slope were used in later stages to assess the hazard potential of a recurring major rockslide. The distinct element code UDEC was used to evaluate the failure mechanism. Elasto-plastic modelling results showed that sliding and shearing along the bedding planes together with brittle fracturing and shearing through the toe of the slope likely had occurred. Runout simulations were carried out using DAN3D. Combinations of rheologies were tested and ranked based on their ability to represent the current distribution of the debris by means of pre-failure topography reconstruction and volume estimates of the deposits. Results showed that the best basal rheological combination for the PRA was frictional during the rockslide and Voellmy when entrainment became important. In contrast, a constant frictional basal rheology best represented the Holocene rock slump. The performance of the present-day state of the slope was tested under different scenarios. Under static condition the slope proved to be stable indicating a stabilized geometrical profile with time. Also, the slope proved to be stable under increased pore water pressures at its toe. Finally the modelled slope was subjected to a seismic load (M=7.8) and its crest failed due to an outward rotation of blocks, probably aided by topographic amplification. The runout simulations showed that the leading edge of the flow could override part of the International Santiago-Mendoza Corridor with no direct impact to the Portillo Ski Resort. Overall, though, under this highly unlikely dynamic condition for the site, the hazard level is very low.

This thesis reports a rock slope hazard investigation located in the Central Andes of Chile, where two significant rock mass wasting events were recognized. Dating using cosmogenic nuclide for ³⁶Cl showed that the deposits were post-glacial in age, corresponding to the Upper Pleistocene Portillo Rock Avalanche (PRA) and a Holocene rock slump and rockslide. The pre-historic landslide deposits underlie both a key transportation route between Chile and Argentina and an important ski resort. The purpose of this research was to investigate the likely failure mechanism and characterise the runout path and volume of the PRA. The insights gained on the back analysis of the slope were used in later stages to assess the hazard potential of a recurring major rockslide. The distinct element code UDEC was used to evaluate the failure mechanism. Elasto-plastic modelling results showed that sliding and shearing along the bedding planes together with brittle fracturing and shearing through the toe of the slope likely had occurred. Runout simulations were carried out using DAN3D. Combinations of rheologies were tested and ranked based on their ability to represent the current distribution of the debris by means of pre-failure topography reconstruction and volume estimates of the deposits. Results showed that the best basal rheological combination for the PRA was frictional during the rockslide and Voellmy when entrainment became important. In contrast, a constant frictional basal rheology best represented the Holocene rock slump. The performance of the present-day state of the slope was tested under different scenarios. Under static condition the slope proved to be stable indicating a stabilized geometrical profile with time. Also, the slope proved to be stable under increased pore water pressures at its toe. Finally the modelled slope was subjected to a seismic load (M=7.8) and its crest failed due to an outward rotation of blocks, probably aided by topographic amplification. The runout simulations showed that the leading edge of the flow could override part of the International Santiago-Mendoza Corridor with no direct impact to the Portillo Ski Resort. Overall, though, under this highly unlikely dynamic condition for the site, the hazard level is very low.