In this contribution, we present new early middle Devonian igneous and metaigneous units with a major juvenile magmatic source input in the North Patagonian Massif, which were discovered through U-Pb and Lu-Hf zircon analyses. Afterward, we assessed their tectonic implications for northwestern Patagonia and then for southern South America, combining our results with available database information consisting of igneous crystallization ages and isotopic data of the Devonian to early Carboniferous magmatic units, tectonic-metamorphic analyses, and thermochronologic record. This study allows for distinguishing retreating and advancing subduction switching in northwestern Patagonia (38°30′ to 44°S) and a contrasting coetaneous evolution for basement outcrops exposed further north (27°30′ and 37°30′S). The early middle Devonian (400–380 Ma) northwestern Patagonian magmatism is characterized by widespread magmatism and positive εHf–εNd linked to forearc and backarc magmatism that evolved within a retreating subduction stage. A tectonic switching toward advancing orogeny stage began in the late Devonian, evidenced by a lull in magmatic activity with a negative εHf–εNd trend, possibly contemporaneous with the first tectonic-metamorphic event in western Patagonia. An early Carboniferous magmatic gap, followed by the subsequent development of the main foliation in the basement during the Carboniferous-Permian period, denotes the acme of this contractional stage. In contrast, the Devonian period in the northern segment is characterized by mostly negative εHf–εNd values, reverse shear zone activity in the foreland, and an inboard magmatism migration, evidencing a compressive tectonic setting that changed to an extensional configuration in the early Carboniferous with widespread arc magmatism development.

The Nevado Volcanic Field (NVF), in southern Mendoza foothills, is part of the Payenia Volcanic Province, a large Quaternary retro-arc volcanic area composed principally of basaltic lava flows and monogenetic volcanoes. Monogenetic volcanism location, distribution and evolution are extremely sensitive to previous rheological discontinuities or faults affecting their basement. With the aim of exploring the subsurface configuration and contributing to a better understanding of this volcanism, we analysed and interpreted aeromagnetic and gravity datasets in addition to structural and volcanic alignments information. Our results show that location of volcanism would have been mainly controlled by NW-SE trending structures. These structures would extend at least to middle crust levels. On the other hand, a secondary control might be related to crustal domains with different densities, which could have affected magma propagation to the surface, hence, controlling the spatio-temporal distribution of volcanoes. The complex interplay between these factors would be responsible for the distribution of volcanic centres. Finally, we discuss the implications of these controls concerning the tectonic stress regime contemporaneous with volcanic activity.

A significant change in the Earth’s climate occurred during the Pliocene–Pleistocene transition. Different external and internal forcings were interrelated in such a way that they promoted the cooling of the climate and environmental changes. We analyzed these changes using a mathematical and statistical approach based on a new algorithm combining Artificial Intelligence and the new multiple cross-wavelet analysis. Although the geomagnetic field (GF) paleointensity showed oscillations over time and not a uniform decay, the results of the Radial Basis Function Artificial Neural Networks showed a long periodicity oscillation with a downward trend practically throughout the Plio–Pleistocene transition. A weakened GF could have allowed an increase in the flux of galactic cosmic rays (GCR) penetrating the Earth’s atmosphere. This led us to hypothesize that, during the Plio–Pleistocene transition, the increase in GCR could have induced a gradual increase in clouds and, therefore, the albedo intensified, causing a progressive decrease in the Earth's surface temperature, as recorded in different paleoclimatic reconstructions of the Plio–Pleistocene. In addition to the known variations in orbital parameters, the GF behavior (the Gauss–Matuyama reversal) and a feasible influence of a coetaneous near supernova event (at less than 100 pc), could have reinforced the climatic forcings towards glacial conditions during the Plio–Pleistocene transition (~ 2.5 Ma).

The Colombian Eastern Cordillera constitutes a region with potential for finding hydrocarbon reserves that are still under-explored, despite the existence of oil and tar sand production. The intense tectonic deformation affects the petroleum systems and increases exploration challenges due to the different generation, maturation, and entrapment conditions that they produce. Diverse geochemical analysis conducted on strategic samples determines that these are likely generated by the same anoxic marine source rock type. Two source rock samples we investigated are characterized by very different biomarker signals as compared to the tar sands and oil samples. Both samples are dominated by hopanes as compared to tri- and tetracyclic terpanes, with very low (Tibasosa Formation) to no (Chipaque Formation) extended tricyclic terpanes. The Soapaga Thrust, along which the analyzed samples are located, has exercised first-rate regional structural control of the distribution of hydrocarbons in the studied area. The uplift of their Mesozoic hanging wall produces intense erosion with sediment transport towards the eastern footwall forming the present infill of the Arcabuco basin. The kitchen areas were connected with the shallower entrapment sectors where excellent reservoir levels such as the Picacho Formation before the Soapaga Thrust movement. The high degree of biodegradation observed in the Picacho Fm. tar sands support early charge before the Soapaga thrust movement, and severe biodegradation following the thrust movement when hydrocarbon supply from the kitchen was interrupted. This work aims to contribute to a better understanding of the geochemical characteristics of the petroleum systems due to the action of the Soapaga Thrust.

This paper revises paleoenvironmental data from Patagonia (southern South America) to discuss the occurrence, characteristics, and human impact of the Medieval Climatic Anomaly (MCA). The analysis of continuous paleoenvironmental archives with multidecadal-to-centennial resolution is based on a quality assessment regarding data interpretation, chronological control, and time range adequacy within the MCA lapse. After applying this three-stepped quality filters on the total dataset (N = 48), 18 cases can accurately be ascribed to the MCA. Except for two sites indicating wetter conditions, these records show dry and/or warm conditions between ca. 750 and 1350 CE (core period at ca. 800–1200 CE). Even though MCA records come mostly from forests and forest-steppe ecotones, all previous archeological hypotheses about the MCA effects on past hunter-gatherers were proposed for the steppes, particularly in southern sectors, thus requiring an assessment of the source of the signal, their synchronicity and causality between human-environmental processes. In the southern steppe, paleoenvironmental records partially overlapping with the MCA time window actually show a predominance of wet conditions between 47° and 50° S, whereas a generalized aridity is recorded in southern tip of the continental Patagonia between 51° and 52° S. Thus, a complex scenario of landscape fragmentation can be supported in the southern steppes during the MCA, produced not only by enhanced aridity in dry environments, but also because of the presence of wet and more resilient areas. This landscape heterogeneity must be considered to deepen the understanding of behavioral changes contemporaneous to the MCA. However, a scenario of demographic growth suggested around 1000 CE for the entire Patagonia could have promoted human changes similar to those expected for the MCA. Finally, no-archeological discussions linked to the MCA were developed for forest regions, despite their robust paleoenvironmental records, implying that changes in proxy data might not have necessarily involved important environmental changes.

This Editorial is based on the recent advances presented in the Special Issues related to tectonics across South America, released in the last three years. Its objective is to display the intense work focused on different lines of research of the Andean and Pre-Andean tectonic field and also to summarize key aspects extracted from these volumes in one single document. These Special Issues describe recent advances related to supercontinent Gondwana formation and posterior peripheral accretions during the Early Paleozoic, the instalment of coetaneous arc along the paleo-Pacific trench, the development of Late Paleozoic basins in the retro-arc region, Early Mesozoic extension related to the break-up of Gondwana, Late Cretaceous-Cenozoic closure of main retroarc depocenters, conformation of the proto-Andes, the growth of their structure and temporal destabilization during the Cenozoic, exhumation degree, paleoenvironmental changes experienced during these processes, and their neotectonic and seismological behavior. In the following paragraphs we will describe their general content and main achievements reached in these volumes.

Between 1966 and 1972, Richard MacNeish led the “Ayacucho Archaeological-Botanical Project” in the Ayacucho Basin, south-central Peru. Over the last decade, we reappraised the lithics recovered in this endeavor. As part of this research, we carried out a detailed review of the lithic remains from the lowest strata of Pikimachay Cave. We concluded that the lithics from layers tentatively dated at about 14,000 uncalibrated yr BP are human-made artifacts, while those from the underlying levels are not. Because of the anthropic nature of the flaked artifacts, their stratigraphic position, chronology, and similarities with other likely coeval lithic assemblages, the Pikimachay record seems to be a good candidate for witnessing possible Paleoamerican foragers living in Ayacucho during the Late Pleistocene.

The dating and routes by which humans colonised South America continue to be debated. Recent research in Uruguay has yielded new Palaeoindian lithic finds from the southern shores of the coastal Merín Lagoon. The author's analysis of a group of Fell points—comparable to other regional examples—shows that this widespread artefact was produced using locally available materials and that they were repeatedly resharpened and repaired until no longer functional. The finds from the Merín Lagoon permit consideration of changing sea levels and their influence on colonisation routes, resource exploitation and archaeological preservation. The Atlantic coastline may have been one possible route of entry for early colonisers of South America.

Here, we discuss the role of the main South American cratonic units in the Columbia and Rodinia supercontinents, and Gondwana megacontinent. According to paleomagnetic and geological data Amazonia and West Africa were linked to Baltica, Laurentia and Siberia forming West Columbia at ca. 1.78-1.75 Ga. The 1.78 to 1.42 Ga paleomagnetic data for Amazonia, Baltica and Laurentia suggest either, that West Columbia preserved its integrity, at least, up to 1.42 Ga, or Amazonia/West Africa broke-up from West Columbia at some time between 1.53 and 1.42 Ga. On the other hand, the Congo-São Francisco, North China, Rio de la Plata, India and proto-Australia formed the East Columbia at ca. 1.78 Ga. However, the presently available Paleo to Mesoproterozoic paleomagnetic data for these cratonic blocks suggest that East Columbia was short-lived. At 1.1 Ga ago, Amazonia/West Africa, Congo-São Francisco, Kalahari and India probably formed a megacontinent that later collided with Laurentia and Baltica forming Rodinia at ca. 1.0 Ga. Most probably, Rodinia broke-up at ca. 750 Ma, when Congo-São Francisco, Kalahari and other smaller blocks rotated ca. 90° counterclockwise, closing the Brasiliano/Clymene Ocean and docked against Amazonia/West Africa and Rio de la Plata at ca. 600-570 Ma ago forming West Gondwana.