An integration of diverse strain markers into a palinspastic reconstruction of the northern Andes provides a first-order quantitative approximation to the response of a complex margin to two ...consecutive arc-continent collisions. A palinspastic reconstruction highlights margin-parallel displacements, with crustal blocks traveling ~400 to ~500 km northward, while the margin-normal shortening component—excluding subduction—is limited to ~100 km. The first arc-continent collision closed a ~500 km-wide ocean basin, where subduction of Atlantic lithosphere took place under an intra-oceanic arc ~90 to ~65 Ma old originally ~1100 km long, and currently stretched ~2200 km. Following collision, eastward-directed oblique subduction started at ~65 Ma, with ~800 km of proto-Caribbean lithosphere consumed under northwestern South America, igniting a short-lived magmatic arc along the post-collisional margin. Two molasse deposits track deformation, cooling, exhumation, and erosion of the margin. The first heralds the arrival of the first intra-oceanic arc to the southernmost northern Andes in late Campanian times, younging-northward as the collision propagated north. This latest Cretaceous molasse deposit records also the first altitudinal gain in the northern Andean orogen along the Central and Real cordilleras. The second molasse follows middle to late Eocene magmatic arc shut down, and regional exhumation and cooling of the margin. Formation, rise and docking of the intra-oceanic Panama arc closed a ~1200 km wide middle Eocene seaway, and renewed Miocene magmatism in the northern Andes, as the Nazca plate started subducting behind the docked arc.
As histórias do México e do Peru compartilham grandes semelhanças culturais em suas representações do mundo. Em seus testemunhos visuais, ambos interagem com elementos simbólicos onde se refletem ...saberes, valores, costumes e tradições que dão sen-tido, valor e identidade às suas comunidades. Muito desse conceito encontra-se no patri-mônio cultural, que deve ser entendido como a memória histórica de um povo; ultrapas-sando em muito a ideia de monumentos e objetos museológicos, para se posicionar como ingrediente de identidade, com capacidade de gerar desenvolvimento e coesão social. Os dois países têm dois exemplos para aprofundar como hoje é possível construir um sentido de identidade a partir do património, recorrendo a manifestações culturais constituídas em dois momentos históricos que marcaram os rumos de ambas as nações e do continente em geral: As Linhas de Nazca durante o período pré-colombiano e cerâmica Talavera no período colonial.
Las historias de México y del Perú, comparten grandes similitudes culturales en sus representaciones del mundo. En sus testimonios visuales, ambas interactúan con elementos simbólicos donde quedan plasmados conocimientos, valores, costumbres y tradiciones que dan sentido, valor e identidad a sus comunidades. Gran parte de este concepto se encuentra en el patrimonio cultural, que debe ser entendido como la memoria histórica de un pueblo; superando con creces la idea de monumentos y objetos de museo, para posicionarse como un ingrediente propio de la identidad, con la capacidad de generar desarrollo y cohesión social. Los dos países poseen dos ejemplos para profundizar sobre cómo en la actualidad, es posible construir sentido de identidad a partir del patrimonio, recurriendo a manifestaciones culturales constituidas en dos momentos históricos que marcaron el rumbo de ambas naciones y el continente en general: Las Líneas de Nazca durante el periodo precolombino y la cerámica de Talavera en el colonial.
The histories of Mexico and Peru share great cultural similarities in their repre-sentations of the world. In their visual testimonies, both interact with symbolic elements where knowledge, values, customs and traditions that give meaning, value and identity to their communities are captured. Much of this concept is found in cultural heritage, which must be understood as the historical memory of a people; far surpassing the idea of monu-ments and museum objects, to position itself as an ingredient of identity, with the ability to generate development and social cohesion. The two countries have two examples to delve into how today, it is possible to build a sense of identity from heritage, resorting to cultural manifestations constituted in two historical moments that marked the course of both nations and the continent in general: The Lines of Nazca during the pre-Columbian period and Talavera pottery in the colonial period.
Arc magmatism plays a key-role in the growth and differentiation of continental crust. In particular, the prolonged magmatic flux events control the genesis of deep crustal hot zones where magma ...accumulation and fractionation favour the continental arc crust evolution and geochemical stratification. In this view long-lived magmatic systems located in arc domains, with their erupted products spanning from basalts to rhyolites are formidable archive for the understanding the evolution of transcrustal magmatic plumbing systems and the construction of a stratified continental crust. This study focuses on the long-lived (ca. 9 Ma) Miocene-Holocene Cordillera de San Buenaventura volcanic system in the Southern Puna Plateau (NW Argentina), a unique natural laboratory where exploring the building up of MASH-zones (or deep crustal 'hot zones') and related sustained volcanism. Synthesis of new and published data, together with new thermobarometry and fractional crystallization modelling, indicates a cyclic scenario with mantle melts undergoing fractional crystallization dominated incipient and waning stages alternate to major mafic magma recharge events during the building up phase of the MASH-zone. This magmatic scenario is also discussed in the light of the coeval geodynamic framework dominated by the subduction of the Nazca plate and the eastward migration of the frontal arc magmatism.
We predict the shape of the outer rise along the Peruvian Trench (6°-21°S) using flexural and gravity modelling in order to study the elastic properties of the subducting/oceanic Nazca Plate (NP). We ...include in our modelling the hotspot swell topography of the Nazca Ridge (NR) in the ridge-trench collision zone (~15°S). Results show an anomalous overthickening of the oceanic crust beneath the NR (from ~6 to 20 km), which is capable to produce most of the swell topography (500–700 km wide and up to 2.2 km high). The swell was formed likely under isostatic conditions (Te ~ 0 km) by the interaction of the NP with a hotspot-spreading center system. Despite the high buoyancy forces of the NR (0.5–4.0 × 1013 N/m) associated to the anomalous thick crust, the 45–50 Ma oceanic NP approaching the Peruvian Trench presents a well pronounced fore-bulge morphology with similar elastic thicknesses (Te = 35 ± 5 km) to those found for cold and old oceanic plate in the western Pacific. Consistently, our results do not show evidence for plate weakening (reduced Te values) in the NR-trench collision zone. We obtain similar results (Te = 40 ± 10 km) north of the NR implying that the oceanic NP is strong prior to subduction along most of the Peruvian convergent margin. This is consistent with the lack of great outer rise events (Mw ≥ 6) and the absence of reduced uppermost mantle velocities offshore Peru suggesting the presence of a poorly hydrated and rigid lithospheric mantle.
Display omitted
•The shape of the outer rise off Peru is predicted by flexural modelling.•The Nazca Ridge overlies an anomalous thick crust and shallow seafloor that was formed under isostatic conditions.•The Nazca Plate at the outer rise presents a well pronounced forebulge with high values of elastic thickness (30 ± 5 km).
The 2019/05/26 Northern Peru earthquake (Mw=8) is a major intermediate-depth earthquake that occurred close to the eastern edge of the Nazca slab flat area. We analyze its rupture process using ...high-frequency back-projection and seismo-geodetic broadband inversion. The latter approach shows that the earthquake propagated with almost purely normal faulting along the 60° eastward dipping plane. Both imaging techniques provide a very consistent image of the peculiar space-time rupture process of this earthquake: its 60-second long rupture is characterized both by a main northward propagation (resulting in a rupture extent of almost 200 km in this direction) and by a reactivation phase of the hypocentral area, particularly active 35 s to 50 s after origin time. Given the depth of this earthquake (125-140 km), the reactivation time window coincides with the arrival time of the surface-reflected elastic wavefield. Computed values of the dynamic Coulomb stresses associated with this wavefield are of the order of ten to several tens of kPa, in a range of values where dynamic triggering has already been observed. The reactivation phase of the Peru earthquake may thus originate from fault areas that were brought close to rupture by the initial rupture front before being triggered by stress increments provided by the reflected wavefield. Source time function complexity observed for other large intermediate-depth earthquakes further suggests that such a mechanism is not an isolated case.
•The 2019 Peru intraslab earthquake did not propagate steadily in the northward direction.•Hypocentral region was reactivated several tens of seconds after rupture origin time.•Dynamic stresses induced by surface-reflected waves favored such delayed reactivation.
We have determined the Wadati–Benioff Zone seismicity and state of stress of the subducting Nazca slab beneath central and southern Peru using data from three recently deployed local seismic ...networks. Our relocated hypocenters are consistent with a flat slab geometry that is shallowest near the Nazca Ridge, and changes from steep to normal without tearing to the south. These locations also indicate numerous abrupt along-strike changes in seismicity, most notably an absence of seismicity along the projected location of subducting Nazca Ridge. This stands in stark contrast to the very high seismicity observed along the Juan Fernandez ridge beneath central Chile where, a similar flat slab geometry is observed. We interpret this as indicative of an absence of water in the mantle beneath the overthickened crust of the Nazca Ridge. This may provide important new constraints on the conditions required to produce intermediate depth seismicity. Our focal mechanisms and stress tensor inversions indicate dominantly down-dip extension, consistent with slab pull, with minor variations that are likely due to the variable slab geometry and stress from adjacent regions. We observe significantly greater variability in the P-axis orientations and maximum compressive stress directions. The along strike change in the orientation of maximum compressive stress is likely related to slab bending and unbending south of the Nazca Ridge.
•Improved earthquake locations and focal mechanisms from new regional datasets.•Slab seismicity patterns indicate the importance of oceanic mantle dehydration in seismogenesis.•Focal mechanisms indicate consistent down-dip extension despite variable slab geometry.•Direction of maximum compression varies significantly depending on local slab geometry.
Hotspots are generated by partial melting due to hot plumes rising within the Earth's mantle, and when tectonic plates move relative to the plume source, hotspot tracks form. Off South America, the ...oceanic Nazca Plate hosts a large population of hotspot tracks. Examples include seamounts formed far from the Pacific-Nazca spreading center (“off-ridge” seamounts), such as the Juan Fernández Ridge (Juan Fernández hotspot), the Taltal Ridge (San Félix hotspot), and the Copiapó Ridge (Caldera hotspot). These hotspot tracks are characterized by a rough and discontinuous topography. Other examples include seamounts formed near the East Pacific Rise (EPR) (“on-ridge” seamounts), such as the Nazca Ridge (Salas y Gómez hotspot) and Easter Seamount Chain (Easter hotspot), and the Iquique Ridge (Foundation hotspot). These oceanic ridges developed a relatively smooth and broad morphology. Here, we present a plate reconstruction of these six oceanic hotspot tracks since the Paleocene, providing a kinematic model of ridge-continental margin collision. For the “off-ridge” seamount group, the plate kinematic reconstruction indicates that the collision point remained quasi-stationary from 40 to 30–25 Ma. Eventually, the southward migration of the collision point of this seamount group accelerated from 23 to 15 Ma (reaching a maxima speed of 300 km/Ma along the trench). From 15 Ma to present the collision point has remained quasi-stationary. The predicted location of the subducted portion of the Taltal, Copiapó and Juan Fernández Ridges coincides with the southward migrating (relative to South America) flat slab segment. For the “on-ridge” seamount group, the kinematic plate reconstruction indicates a continuous southward migration of the collision point from ~23 Ma, which is related to the fragmentation of the Farallon Plate. The southward migration accelerated until 15 Ma, reaching approximately 150 km/Ma. From 15 Ma to present, the southward migration has been decelerating except an increment of the migration velocity during the Chron 4 due to an increase of the convergence velocity. The migration velocity differences between the on-ridge and off-ridge hotspot tracks are mainly result from the hotspot track azimuth and the margin azimuth on the collision point. Convergence velocity varies along the trench, but it is a minor factor comparing different hotspot tracks migration velocity. Due to the EPR-plume interactions, our reconstruction suggests that the eastern Tuamotu Island Plateau formation occurred 48–27 Ma on the Easter Hotspot, which was located near to the EPR segment between the Marquesas and Austral Fracture Zones. Our model also predicts that the Iquique Ridge seamounts track is consistent with the position of the Foundation hotspot. The Foundation hotspot jumped to the Challenger (Resolution) Fracture Zone from the Farallon plate to the Pacific plate. This process triggered the cessation of the Iquique Ridge volcanic formation, and initiated volcanism at Foundation Chain in the Pacific Plate at ~25 Ma.
Display omitted
•We present a plate reconstruction model for the Hotspot tracks in the Nazca Plate.•We show a paleo-bathymetric reconstruction from 60 Ma to present off South America.•We provide a kinematic model of ridge-trench collision off South America.
The amphinomid polychaete Chloeia rozbaczyloi sp. nov., collected from seamounts of the Nazca Ridge (NR), northwest of Desventuradas islands, southeastern Pacific Ocean, is described. The new species ...was observed on only two of seven seamounts surveyed in the area (25.079°S, 82.006°W, and 25.408°S, 81.769°W, ∼220 m depth), being abundant on one of them.
Specimens were observed under optical and scanning electron microscopes, and DNA was sequenced (COI, 16S, 18S, and 28S nucleotide alignment). Chloeia rozbaczyloi sp. nov. belongs to the venusta group of Chloeia and is distinguished mainly by: (i) the chromatic pattern of the dorsum (with a single middorsal dark band) and the caruncle (with 16–20 vertical folds and 12 to 14 black spots posteriorly decreasing in diameter), (ii) by the bi-annulated dorsum of the first ten chaetigers, each with a bean-shaped anterior pseudosegment, (iii) long neuropodial cirri, with a short ceratophore, at chaetiger 2 and reaching chaetiger 6, and (iv) bipinnate branchiae from chaetiger 4, with seven to nine lateral branches arising from the primary axis, each possing five pinnules; branchiae change progressively in size to the posterior end. The ciliated margin of the accessory dorsal cirri suggests a respiratory function that might be relevant considering that both seamounts in which the species was observed could be influenced by low-oxygen waters. DNA results further support that C. rozbaczyloi sp. nov. differs from the other five congeneric taxa (C. bimaculata, C. flava, C. parva, C. pocicola, and C. viridis) for which genetic information is available.
This finding constitutes the first report of the genus for Chilean waters, increasing the number of species of Amphinomidae in this area to seven. It also confirms the presence of the family in the NR and increases the number of Chloeia species in the world to 43.
The seamounts where the new species have been collected are within the newly created offshore Nazca-Desventuradas Marine Park. Information on potentially unique and endemic species, such as the one discussed here, is of utmost importance to preserve special ecological units, address ecosystem services, and implement management measures in the area.
•A new species of amphinomid polychaete, Chloeia rozbaczyloi sp. nov. is described.•The new species inhabits poorly explored seamounts of the remote Nazca Ridge off Chile.•This finding constitutes the first report of the genus Chloeia for Chilean waters.•Genetic data for Chloeia rozbaczyloi sp. nov is provided.•The new species is reported for seamounts lying within the recently created Nazca Desventuradas Marine Park.
During the Miocene, the evolution of the Northern Andes was influenced by the subduction of the young Oceanic Nazca Plate and the final collision of the Panama-Chocó Block (PCB) with the continental ...margin of Colombia. This work presents an integrated field, geochemical, Hf-Nd-Sr isotopic and geochronological study of volcanic arc front rocks of the Combia volcanic complex in the northern segment of the Cauca-Valley (North of 5°N) in order to reconstruct the petrologic and tectonic significance of a short life arc with a very heterogeneous geochemical signature. The Combia volcanic complex includes a series of basalts, andesites, pyroclastic rocks, porphyritic andesitic-dacitic domes, and dacitic to andesitic porphyries, with zircon UPb crystallization ages between 8.5 and 5.2 Ma. Negative anomalies of Nb and Ti, enrichment in Light Rare Earth Elements (LREE) and depletion in Heavy Rare Earth Elements (HREE) are characteristic of magma origin in a convergent margin setting. This magmatism shows different tholeiitic, calc-alkaline, and adakite-like geochemical signatures, which may be related to an initial adiabatic-controlled dry melting, followed by wet melting conditions from the hydrated mantle wedge. Variations in crustal thickness between 17 and 45 km estimated by the Ce/Y, La/Yb, and Sr/Y ratios are related to local thinning of a previously thickened continental crust. Such pattern can be explained by strain partitioning in which crustal thinning may be a relatively local phenomenon. Arc magmatism in this segment of the margin apparently migrates eastward from the Western Cordillera to the Cauca-Valley between 11 and 9 Ma and was followed by a magmatic quiescence after ~5.2 Ma. This spatio-temporal history is consistent with continuous oblique convergence of the Nazca Plate and slab flattening beneath the continental margin until it achieves its modern tectonic configuration.
Display omitted
•Short duration arc magmatism•Compositionally and petrogenetically heterogeneous magmatism•Oblique convergence magmatic tracer•Changing nature of the Nazca plate subduction in the Northern Andes
Recent earthquakes in Chile, 2014, Mw 8.2 Iquique, 2015, Mw 8.3 Illapel and 2016, Mw 7.6 Chiloé have put in evidence some problems with the straightforward application of ideas about seismic gaps, ...earthquake periodicity and the general forecast of large megathrust earthquakes. In northern Chile, before the 2014 Iquique earthquake 4 large earthquakes were reported in written chronicles, 1877, 1786, 1615 and 1543; in North-Central Chile, before the 2015 Illapel event, 3 large earthquakes 1943, 1880, 1730 were reported; and the 2016 Chiloé earthquake occurred in the southern zone of the 1960 Valdivia megathrust rupture, where other large earthquakes occurred in 1575, 1737 and 1837. The periodicity of these events has been proposed as a good long-term forecasting. However, the seismological aspects of historical Chilean earthquakes were inferred mainly from old chronicles written before subduction in Chile was discovered. Here we use the original description of earthquakes to re-analyze the historical archives. Our interpretation shows that a-priori ideas, like seismic gaps and characteristic earthquakes, influenced the estimation of magnitude, location and rupture area of the older Chilean events. On the other hand, the advance in the characterization of the rheological aspects that controlled the contact between Nazca and South-American plate and the study of tsunami effects provide better estimations of the location of historical earthquakes along the seismogenic plate interface. Our re-interpretation of historical earthquakes shows a large diversity of earthquakes types; there is a major difference between giant earthquakes that break the entire plate interface and those of Mw ~ 8.0 that only break a portion of it.
•Recently 4 large earthquakes occurred in Chile, inside active seismic zones.•Mostly of Chilean Eqs Mw ~8.0 break the middle or the bottom of the plate interface.•Chile seismicity is characterized by short time sequences of Eqs and super-cycles.
PDF
