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The interaction of the northern Nazca and southwestern Caribbean oceanic plates with northwestern South America (NWSA) and the collision of the Panama‐Choco arc (PCA) have significant implications on the evolution of the northern Andes. Based on a quantitative kinematic reconstruction of the Caribbean and Farallon/Farallon‐derived plates, we reconstructed the subducting geometries beneath NWSA and the PCA accretion to the continent. The persistent northeastward migration of the Caribbean plate relative to NWSA in Cenozoic time caused the continuous northward advance of the Farallon‐Caribbean plate boundary, which in turn resulted in its progressive concave trench bending against NWSA. The increasing complexity during the Paleogene included the onset of Caribbean shallow subduction, the PCA approaching the continent, and the forced shallow Farallon subduction that ended in the fragmentation of the Farallon Plate into the Nazca and Cocos plates and the Coiba and Malpelo microplates by the late Oligocene. The convergence tectonics after late Oligocene comprised the accretional process of the PCA to NWSA, which evolved from subduction erosion of the forearc to collisional tectonics by the middle Miocene, as well as changes of convergence angle and slab dip of the Farallon‐derived plates, and the attachment of the Coiba and Malpelo microplates to the Nazca plate around 9 Ma, resulting in a change of convergence directions. During the Pliocene, the Nazca slab broke at 5.5°N, shaping the modern configuration. Overall, the proposed reconstruction is supported by geophysical data and is well correlated with the magmatic and deformation history of the northern Andes. Plain Language Summary: The tectonic reconstruction in convergent triple junctions is a particularly challenging task as the relative motion between plates could define highly changing boundaries. Indeed, the resulting interaction between these convergent plates may induce important changes in the disposition of the trenches, and in turn in the three‐dimensional geometry of the subducting plates. Therefore, these highly dynamic conditions throughout geological time may be accommodated by different phases of plate fragmentation and reorganization. These factors could explain the complex spatial‐temporal distribution of subduction‐related magmatism and the different episodes of deformation in the upper plates. This reasoning is validated in the northwestern corner of South America (SA), where the continent has been converging against the Caribbean and Farallon‐derived oceanic plates since Cretaceous time. Additionally, we study the effects of the collision and accretion of the Panama‐Choco arc with SA. To accomplish that, we review the kinematic history of the Farallon/Nazca and Caribbean oceanic plates relative to stable Guiana Craton (SA) and integrate these results with the magmatic and deformation evolution of the northern Andes, which allow us to propose a model of the geometrical evolution of the subducting slabs. The obtained model is additionally constrained by seismological data and published velocity anomalies. Key Points: The tectonics of convergent triple junctions is complicated by the relative plate motion and interaction of the involved platesWe propose a model for the kinematic and geometric evolution of the Farallon/Nazca and Caribbean plates throughout the CenozoicThe interaction between the Caribbean, Nazca and South American plates is closely related to the deformation history in the Northern Andes [ABSTRACT FROM AUTHOR]

This paper presents a detailed geological map at the 1:20,000 scale of the Tocomar basin in the Central Puna (north-western Argentina), which extends over an area of about 80 km2 and displays the spatial distribution of the Quaternary deposits and the structures that cover the Ordovician basement and the Tertiary sedimentary and volcanic units. The new dataset includes litho-facies descriptions, stratigraphic and structural data and new 234U/230Th ages for travertine rocks. The new reconstructed stratigraphic framework, along with the structural analysis, has revealed the complex evolution of a small extensional basin including a period of prolonged volcanic activity with different eruptive centres and styles. The geological map improves the knowledge of the geology of the Tocomar basin and the local interplay between orogen-parallel thrusts and orogen-oblique fault systems. This contribution represents a fundamental support for in depth research and also for encouraging geothermal exploration and exploitation in the Puna Plateau region. [ABSTRACT FROM AUTHOR]

Volcano sector collapses are catastrophic events that can mobilize huge volumes of material and cause changes in the magmatic plumbing system, leading to variations in growth rate and/or composition. Dating pre-historic volcanic debris avalanche deposits is challenging. Geological materials directly recording avalanche formation and amenable to radiometric dating are rare, and, in the case of Holocene events, the applicable radiometric dating techniques are scarce. Socompa volcano suffered the largest collapse event in the Central Volcanic Zone of the Andes, producing one of Earth's most spectacular and best-preserved volcano avalanche deposits. We apply multiple dating techniques to unravel the timing of Socompa's collapse and gain insights into its pre- and post-collapse eruptive history. The age of the collapse event is constrained by a 14C age of 6,200–6,400 BP of a paleosol buried by the avalanche, and by a post-collapse lava flow dated at 5.91 ± 0.43 ka by zircon double-dating. Bayesian age sequence modeling integrating these ages determines that the collapse occurred at 6.18 - 0.64 + 0.28 ka. Four zircon eruption dates and one unspiked K–Ar age between 69.2 ± 6.0 and 22.1 ± 1.9 ka constrain the age of the youngest stage of activity before the collapse. The ages, together with paleosurface modeling and volume calculations, allow estimating growth rates for the young pre-collapse and post-collapse stages of ~ 0.2–0.3 km3/kyr and ~ 0.5–2 km3/kyr, respectively, indicating a significant increase in activity after the collapse event. The collapse may have triggered a new growth phase or accelerated an ongoing one and was likely associated with a Plinian eruption that produced widespread pumice fallout. The pre- and post-collapse lavas have similar compositions and zircon crystallization age distributions, suggesting that the same or a similar magma reservoir was tapped before and after the collapse. Thus, huge collapses such as Socompa's event can promote increased volcanic activity as a consequence of the unloading effect, but the overall plumbing system may not be affected enough to show significant variations in erupted compositions, at least transiently. Our results highlight the efficacy of the zircon double-dating method for dating very young felsic lavas and for constraining the age of debris avalanche deposits. This is particularly relevant in the Andean Central Volcanic Zone and other regions with arid climates, where organic material is rare and hence 14C dating is often unfeasible. Furthermore, the post-collapse zircon eruption age of 5.91 ± 0.43 ka is the youngest radiometric age yet obtained for a lava flow in the southern Central Volcanic Zone, highlighting the youth of volcanic activity at Socompa, and confirming its status as a Holocene active volcano. [ABSTRACT FROM AUTHOR]

The hinterland zone of the North Patagonian Andes between 41° and 43°S constitutes a poorly explored sector of the Andes, where no structural studies and scarce geochronological determinations have been carried out. This paper focuses on two isolated volcanic sections hosted at the main Andes, in which field evidence indicates a common synextensional origin. Geochronological data establish that this volcanic event occurred diachronously at the innermost sector of the evolving fold and thrust belt, during middle to late Miocene times. Therefore, the event was briefly coeval and postdated compressive tectonics recognized in the deformational front and correlative to the last phase of pluton emplacement of the North Patagonian Batholith. Local-scale topographic swath profiles performed in this work reveal negative topographic anomalies where normal faults were recognized. Moreover, regional swath profiles show not only a conspicuous depressed zone at the hinterland zone, where the studied sections are located, but also anomalously high altitudes at the foreland zone. In addition, calculated orogenic volumes increase in this sector of the fold and thrust belt, which agrees with recent shortening estimations. These topographic along-strike variations, in association with late Miocene extension following the main compressive stage in the area, are explained by a supercritical stage of the orogenic wedge that would have led to focused extension at the innermost sector of the fold and thrust belt. [ABSTRACT FROM AUTHOR]

The rate of ocean‐crust production exerts control over sea level, mantle heat loss, and climate. Different strategies to account for incomplete seafloor preservation have led to differing conclusions about how much production rates have changed since the Cretaceous, if at all. We construct a new global synthesis of crust production along 18 mid‐ocean ridges for the past 19 Myr at high temporal resolution. We find that the global production rate during 6–5 Ma was only 69%–75% of the 16–15 Ma interval. The reduction in crust production is mostly due to slower seafloor spreading along almost all ridge systems. While the total ridge length has varied little since 19 Ma, some fast‐spreading ridges have grown shorter and slow‐spreading ridges grown longer, amplifying the spreading‐rate changes. Our production curves represent a new data set for investigating the forces driving plate motions and the role of tectonic degassing on climate. Plain Language Summary: The question of whether the speeds of tectonic plates vary over time is controversial but has big‐picture implications for our understanding of the forces inside the Earth that drive the plates, the role of volcanoes in controlling climate change over millions of years, and the rise and fall of sea level. At mid‐ocean ridges, two plates move apart, and the volcanic rocks that comprise the ocean crust are created. Magnetic minerals in the rocks record their age of formation and therefore the relative speeds of the diverging plates. However, this record is incomplete because seafloor is destroyed at subduction zones. We used the preserved seafloor magnetic record to calculate diverging plate speeds over the past 19 million years. We find that the relative plate speed at almost all divergent plate boundaries has slowed down, with a major inflection point at 15–16 Myr. As a result, the rate at which new ocean crust is created also slowed down, by roughly 35%. We speculate that there is not a single explanation for the nearly global slowdown in plate speeds but rather several unrelated tectonic events, such as the emergence of the Andes. Key Points: A new global synthesis of seafloor‐spreading rates at high temporal resolution is presentedSince 15 Ma, spreading rate decreased along 15 of 18 major ridge systems, with a total global reduction of 37%High‐resolution reconstructions, new data for eastern Pacific, and astronomical ages allow more detail than previous studies [ABSTRACT FROM AUTHOR]

Abstract: This paper summarizes geological data from the basement massifs of the northern Andes. Geological and geochronological data from this region indicate that the metamorphic basement consolidated during the Orinoquiense (∼1.0Ga) and Caparonensis (∼0.47Ga) orogenic events. The latter formed part of a proto-Andean orogen that extended from Venezuela to northern Argentina. Interactions between Laurentia and the peri-Amazonian proto-Andes during Late Proterozoic–Paleozoic times, is supported by geological, geochronological, isotopic data and by faunal affinities of the sedimentary sequences overlying the basement complex. This interaction may have included possible terrane transfer between Laurentia and Amazonia. Geological, tracer–isotopic and geochronological data suggest that a fragment of the proto-Andean orogen is presently located at the southern end of Mexico (Oaxaquia). The transfer of Oaxaquia from the northern termination of the proto-Andes, most likely occurred in late Paleozoic time and was left attached to N. America upon the disaggregation of Pangea. [ABSTRACT FROM AUTHOR]

Abstract: This paper evaluates the chronology of the last glacial cycle and deglaciation in the Lago Pueyrredón valley of central Patagonia, 47.5° S, Argentina. The valley was a major outlet of the former Patagonian Ice Sheet and the moraines that record its fluctuations are an important proxy record of climate change in southern South America. Such moraines are well-preserved in the Lago Pueyrredón valley owing in part to the semi-arid environment east of the mountain front. Here, we provide the first direct chronology for the age of the “Rio Blanco” moraine system by utilizing cosmogenic-nuclide surface exposure ages. Boulders on the moraines give 10Be exposure ages that indicate the Last Glacial Maximum (LGM) maximum extent occurred by 27–25ka. Subsequent advances occurred at 23–22ka, 20–18ka, and ca. 18–17ka. Initial deglaciation began after ca. 18–17ka and was interrupted as evidenced by the Lago Columna moraines up-valley. Subsequently the outlet glaciers occupying both the Lago Pueyrredón basin (Chilean name: Lago Cochrane) and the Lago Buenos Aires basin (Chilean name: Lago General Carrera) to the north, rapidly retreated more than 80km at around 16.5–15ka. The timing of the LGM maximum extent and the onset of deglaciation occurred broadly synchronously throughout Patagonia. Deglaciation resulted in a series of interconnected glacier-dammed lakes in the region that initially drained toward the Atlantic Ocean and later drained to the Pacific Ocean as a consequence of disintegrating ice in the Andes. [Copyright &y& Elsevier]

Abstract: This paper documents the occurrence of the Little Ice Age (LIA) in the El Azufre and El Peñón glaciers at 35°S and in the Las Choicas and Las Damas glaciers at 34°55′S in the headwaters of the Rio Grande basin in the Central Andes of Argentina. Moraine morphology, stratigraphic relationships, radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the LIA advance in this area. The LIA maximum advance occurred between cal. yr 1550 and 1720 AD, and a readvance occurred around cal. yr 1830 AD. In addition, glacier fluctuations of the Las Vacas and Güssfeltd glaciers (33°S) and El Peñón and El Azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs, and satellite images. The glaciers showed a marked retreat during 1894–2007. Minor readvances occurred in the 1980s and 1990s, which could be related with strong warm ENSO events during these decades. Our results are consistent with observations made by other authors in the region. [Copyright &y& Elsevier]

Abstract: This paper presents an updated, extensive review of glacier fluctuations during the past 1000years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations. [Copyright &y& Elsevier]

Since the Archean, secular change in orogenic style is demonstrated through evolution of metamorphic conditions and geochemical proxies. Linked to orogenic style is the amount of crustal thickening and elevation, whereas orogenic vigor is related to the supercontinent cycle. An array of Proterozoic orogens spanned the assembly of supercontinents Columbia and Rodinia, but the vigor of orogenesis is debated, with proposals for both Mesoproterozoic quiescence and climax. We show mid‐Proterozoic orogenesis occurred globally and was broadly continuous; furthermore, orogens exhibit elevated metamorphic thermobaric ratios with large volumes of high‐temperature felsic magmatic rocks. These features reflect higher mantle heat flux leading to increased mid‐crustal flow and lower elevation. In this context, proposals that geochemical proxies for crustal thickness record orogenic quiescence are inconsistent with the geological record. Alternatively, secular change in crustal thickness is attributed to orogenic style, namely the prevalence of hot, thin, and low orogens in the mid‐Proterozoic. Plain Language Summary: Orogenesis is the process whereby tectonic plates converge and mountain systems are created. In the case of the Andes and Himalayas, orogenesis resulted in significant thickening of the continental crust. Recent attempts to provide geochemical proxies for crustal thickness have allowed geologists to track the thickness of the crust through geologic time. One period of time in particular between 1850 and ∼850 million years ago—the mid‐Proterozoic—was characterized as having relatively thin crust. Some have argued this is evidence for a period of "orogenic quiescence." However, the geologic record is rife with ancient orogenic belts during this time as evidenced by the metamorphic and igneous rock records. In particular, the metamorphic rocks display higher than normal temperature/pressure ratios indicating unusually hot crust. We propose that the thin crust at this time is a product of high temperatures resulting in greater crustal flow and therefore lower mountain ranges. Key Points: The mid‐Proterozoic was characterized by unusually hot orogenesisElevated orogenic temperatures limited crustal thickening and promoted crustal flow and hinterland extensionSecular change in orogenic process explains independent estimates of variation in Proterozoic crustal thickness [ABSTRACT FROM AUTHOR]

This paper reports the presence of xenocrystic zircons in sub-volcanic rocks (Guarco Andesite and Porphyritic Intrusives units) exposed in the northeast of the Western Cordillera of Colombia (WCC) and provides a new contribution to the understanding of the tectono-magmatic evolution of the area during the Upper Cretaceous associated with the geological history of the Caribbean Large Igneous Province (CLIP). The study area is located in an accretionary terrane constituted by a basement of oceanic affinity (Barroso Formation and San José de Urama Diabases unit), amalgamated against the northwestern South American margin and associated with the development of CLIP. The elemental and isotopic geochemical data (with an initial ratio of 87Sr/86Sr between 0.70334 and 0.70543 and ε Νd between +6.25 and + 7.42) indicate an island arc environment for the formation of sub-volcanic rocks and a mantle wedge source area (and/or the arc itself), which presents subordinate levels of crustal material. U-Pb zircon ages by SHRIMP IIe and LA-ICP-MS show ages from the Mesoarchean to the Upper Cretaceous, with representative peaks of approximately 2700, 2100, 600 and 90 Ma. The younger age population is interpreted as the crystallization age of the studied rocks and indicates a spatial and temporal relationship with the basement rocks associated with the CLIP. The older zircons are interpreted as xenocrysts coming from terrigenous sediments that were dragged down into the subduction channel (reflecting crustal recycling processes through the mantle in subduction zones). Alternatively, the xenocrystic zircons could have come from the assimilation of crustal sediments that were previously deposited over the primitive arc. We suggest that the source areas of zircon xenocrysts probably are located close to the Arequipa Massif and the Marañon Complex inliers, and close to the ensialic Basement of the Central Cordillera of Colombia (CCCB). Using these source areas and paleogeographic/paleomagnetic models published by other authors, we propose two possible paleogeographic scenarios differentiated by the polarity of the subduction zone. • Crustal recycling evidence an intra-oceanic subduction system, through the presence of xenocrystic zircons in arc rocks accreted to continental margins. • Mesoarchean to Paleozoic xenocrystic zircons are hosted in Cretaceous sub-volcanic rocks that intruded the oceanic basement rocks. • Origin of the older zircons is interpreted as xenocrystals coming from terrigenous sediments that were dragged into the subduction channel and/or previously deposited in the primitive island arc (Barroso Arc). • Potential provenance areas of the xenocrystic zircons correspond to areas along the NW margin of South America. • We proposed a geodynamic/paleogeographic implications for the northeast of the Western Cordillera of Colombia during the Upper Cretaceous. [ABSTRACT FROM AUTHOR]

Crustal faults at subduction zones show evidence of activity over geological time, but at the scale of earthquake cycle the mechanical behavior of these faults is not fully understood. Here we construct 2-D viscoelastic models constrained by both horizontal and vertical GPS-derived interseismic velocities to investigate the contribution and interrelation between subduction zone locking, viscous mantle flow, and upper plate faulting on surface deformation in Central Andes. Main pattern of horizontal velocities can be explained by a combination of locking degree and viscous flow, whereas vertical signal is found essential for estimating the locking depth. A sharp deformation gradient near the major back-arc fault suggests an active interseismic shorting across this structure. We further conduct mechanical viscoelastic models with a frictional back-arc fault to analyze its displacement and activation conditions. Our results suggest that the back-arc fault is creeping at ~ 3 mm/year and its motion is mainly driven by the interseismic viscous mantle flow, which spreads plate tectonic stresses broadly across the continent. Moreover, the frictional strength of the back-arc fault must be remarkably weak and its mechanics re-distributes the interseismic deformation and shortens the continental plate in Central Andes. Geological estimates suggest that the long-term shortening rate at the back-arc fault is ~ 10 mm/year, suggesting that this structure can accumulate ~ 7 mm/year of slip deficit, confirming the seismic potential of this structure. [ABSTRACT FROM AUTHOR]

Three tectonic units have been recognized in the Chifeng area, Inner Mongolia, from north to south, including the Qiganmiao accretionary prism, Jiefangyingzi arc belt and Sidaozhangpeng molasse basin, which formed an Andean‐type active continent margin during the early to middle Paleozoic. The Qiganmiao accretionary prism is characterized by a mélange that consists of gabbro, two‐mica quartz schist and basic volcanic rock blocks and heterogeneously deformed marble matrix. Two zircon U‐Pb ages of 446.0±6.3 Ma and 1104±27 Ma have been acquired and been interpreted as the metamorphic and forming ages for the gabbro and two‐mica quartz schist, respectively. The prism formed during the early to middle Paleozoic southward subduction of the Paleo Asian Ocean (PAO) and represents a suture between the North China craton (NCC) and Central Asian Orogenic Belt (CAOB). The Jiefangyingzi arc belt consists of pluton complex and volcanic rocks of the Xibiehe and Badangshan Formations, and Geochronology analysis indicates that the development of it can be divided into two stages. The first stage is represented by the Xibiehe Formation volcanic rocks, which belong to the subalkaline series, enriched LREE and LILE and depleted HFSE, with negative Eu anomalies, and plot in the volcanic arc field in discrimination diagrams. These characters indicate that the Xibiehe Formation results from to the continental arc magmatic activity related to the subduction of the PAO during 400‐420 Ma. Magmatism of the second stage in 380‐390 Ma consists of the Badangshan Formation volcanic rocks. Geochemistry analysis reveals that rhyolite, basaltic andesite and basalt of the Badangshan Formation were developed in continental margin arc setting. Moreover, the basaltic andesite and basalt display positive Sr anomalies, and the basalt have very low Nb/La values, suggesting that fluid is involved in magma evolution and the basalts were contaminated by continental crust. The sequence of Sidaozhangpeng molasse basin is characterized by proximity, coarseness and large thickness, similar to the proximity molasses basin. According to our field investigation, geochronological and geochemical data, combined with previous research in this area, a tectonic evolutionary model for Andes‐type active continental margin of the CAOB has been proposed, including a development of the subduction‐free PAO before 446 Ma, a subduction of the PAO and arc‐related magmatism during 446‐380 Ma, and formation of a molasse basin during 380‐360 Ma. [ABSTRACT FROM AUTHOR]

Abstract  New U–Pb, Re–Os, and 40Ar/39Ar dates are presented for magmatic and hydrothermal mineral phases in skarn- and porphyry-related ores from the Nambija and Pangui districts of the Subandean zone, southeastern Ecuador. Nambija has been one of the main gold-producing centers of Ecuador since the 1980s due to exceptionally high-grade ores (average 15 g/t, but frequently up to 300 g/t Au). Pangui is a recently discovered porphyry Cu–Mo district. The geology of the Subandean zone in southeastern Ecuador is dominated by the I-type, subduction-related, Jurassic Zamora batholith, which intrudes Triassic volcanosedimentary rocks. The Zamora batholith is in turn cut by porphyritic stocks, which are commonly associated with skarn formation and/or porphyry-style mineralization. High precision U–Pb and Re–Os ages for porphyritic stocks (U–Pb, zircon), associated prograde skarn (U–Pb, hydrothermal titanite), and retrograde stage skarn (Re–Os, molybdenite from veins postdating gold deposition) of the Nambija district are all indistinguishable from each other within error (145 Ma) and indicate a Late Jurassic age for the gold mineralization. Previously, gold mineralization at Nambija was considered to be Early Tertiary based on K–Ar ages obtained on various hydrothermal minerals. The new Jurassic age for the Nambija district is slightly younger than the 40Ar/39Ar and Re–Os ages for magmatic–hydrothermal minerals from the Pangui district, which range between 157 and 152 Ma. Mineralization at Nambija and Pangui is associated with porphyritic stocks that represent the last known episodes of a long-lived Jurassic arc magmatism (∼190 to 145 Ma). A Jurassic age for mineralization at Nambija and Pangui suggests that the Northern Andean Jurassic metallogenic belt, which starts in Colombia at 3° N, extends down to 5° S in Ecuador. It also adds a new mineralization style (Au-skarn) to the metal endowment of this belt. [ABSTRACT FROM AUTHOR]