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.

The Paleocene-Eocene Catán Lil Ignimbrite (CLI) is one of the few occurrences within the explosive acid volcanism of this age in the extra-Andean region of the North Patagonian Massif. It represents a small-scale explosive eruption covering an area of 214 km2, with an estimated volume of 1.27 km3 and consisting of three weakly-to densely welded cooling units. The maximum thickness of this sequence is 90 m. Its basal unit is the best preserved, and has allowed a lithofacial analysis that reveals different aspects of the eruption and the emplacement mode of the Catán Lil pyroclastic flows. The CLI ignimbrites are generally massive, poorly sorted, matrix-supported deposits (tuff and lapilli tuff) resulting from dense pyroclastic currents (PDCs). They are composed mainly of juvenile fragments, scarce lithoclasts and crystalloclasts, being a product of a purely magmatic fragmentation occurred at a shallow level. A pyroclastic fountaining eruptive model is interpreted, resulting from the collapse of a low eruptive column, and a rapid and high-temperature emplacement. The CLI PDCs generally respond to slow moving pyroclastic flows with low erosive energy. The morphology and stratigraphy indicate radial emissions with thicknesses decreasing towards the periphery that become evident in Central-South ignimbrites. These PDCs flowed over a planar terrain, giving rise to most of the CLI deposits (South-Central area and North- East). The Northwestern ignimbrites are deposits in the interior (south and middle part) of the Catán Lil creek, forming thick deposits within the latter valley and thin, veneer-like deposits over the flanking Lipetrén granitoids. In the North- East region, the ignimbrites show stratigraphic relationships that suggest that the PDCs would slightly postdate those of the South-Central area. The Catán Lil Ignimbrites represent the most eastern exposures of the Paleocene-Eocene Pilcaniyeu Belt, differing from the latter in that it lacks a conspicuous lava facies, and by the unimodal character and the tectonic signature of the Catán Lil sequence.

The Pampas plains of southern South America were predominantly dry, eolian-shaped landscapes, besides some interposed humid phases, during most of the late Pleistocene-Middle Holocene, evolving to humid-subhumid grasslands hosting an increasingly large number of shallow lakes in the late Holocene. These lakes proved to preserve in their sediments worthy evidence to interpret past environmental-ecological conditions, offering tools to analyze climatic variability and human impacts during the last millennia. This is the case of the shallow lake Primera Laguna, located in the western and driest edge of the Pampas. Here, we present a multiproxy study from this shallow lake with the aims of contributing to reconstruct its past stages, infer the climatic scenarios that drove its evolution, evaluate the potential anthropogenic role in these changes, and correlate/analyze this record with available data from other Pampean lakes. We analyzed a high-resolution palynological record, accompanied by macroscopic charcoal accumulation rates, C/N, C and N stable isotopes, magnetic susceptibility, and sediment geochemistry, of a 41-cm long sediment core, extracted from the deepest sector of the lake. An age-depth model based on AMS chronology indicates a preserved lake history for the past ∼1400 cal yr BP. Ecological and sedimentological interpretations allowed us to propose four main periods during this time lapse. For the first period (1375–1069 cal yr BP, 575–881 CE), the integrative interpretation indicates a very low shallow lake –mostly oligotrophic, alkaline, and clear water–, dominated by the accumulation of epiclastic silty fine sand from the surrounded eolian landscape and covered by xerophytic vegetation. In the second period, between 1069 and 738 cal yr BP (881–1212 CE), we inferred a trend to rising lake levels and mesotrophic conditions, and more pollen taxa than the previous period, and with lake margins dominated by cattails and sedges. The third period (738–193 cal yr BP, 1212–1757 CE) was characterized by more variable and lower lake levels compared to previous periods and more frequent desiccation processes at the lake margins. Then, during the fourth period (last 195 cal yr, 1757–2015 CE), there was a gradual transition towards a larger and more stable shallow lake with a deeper water column, and under a turbid state probably related to eutrophication. From the comparison between Primera Laguna record and the previously studied Nassau shallow lake, located in the same eolian landscape, we found a synchronic evolution, implying common drivers of change in terms of climatic variability and human impact. Correlation with shallow lakes from the more humid belt of the Pampas suggests widespread increases of water availability in the region since ∼1500 cal yr BP, variable/lower lake levels during ∼600–200 cal yr BP, and a shift to positive hydrological balances up to the present highstands.

Paleomagnetic poles used to compute apparent polar wander paths (APWPs) are strongly dispersed, which was recently shown to cause a large fraction (>50%) of these poles to be statistically distinct from the APWP to which they contributed, suggesting that current statistical approaches overestimate paleomagnetic resolution. Here, we analyze why coeval paleopoles are so dispersed, using the paleopoles behind the most recent global APWP and a compilation of paleomagnetic data obtained from <10 Ma volcanic rocks (PSV10). We find that paleopoles derived from sedimentary rocks, or from data sets underrepresenting paleosecular variation (PSV), are more dispersed and more frequently displaced. We show that paleopoles based on a smaller number of paleomagnetic sites are more dispersed than poles based on larger data sets, revealing that the degree to which PSV is averaged is an important contributor to the pole dispersion. We identify as a fundamental problem, however, that the number of sites used to calculate a paleopole, and thus the dispersion of coeval paleopoles, is essentially arbitrary. We therefore explore a different approach in which reference poles of APWPs are calculated from site-level data instead of paleopoles, thereby assigning larger weight to larger data sets. We introduce a bootstrap-based method for comparing a collection of paleomagnetic data with a reference data set on the same hierarchical level, whereby the uncertainty is weighted against the number of paleomagnetic sites. Finally, our study highlights that demonstrating smaller tectonic displacements requires larger paleomagnetic data sets, and that such data sets can strongly improve future APWPs.