Tierra Del Fuego Research Articles

SNP genotyping revealed a hybrid zone between Mytilus chilensis and M. platensis in southern South America (the Strait of Magellan, Isla Grande de Tierra del Fuego and the Falkland Islands).

Hybrid zones among mussel species have been extensively studied in the northern hemisphere. In South America, it has only recently become possible to study the natural hybrid zones, due to the clarification of the taxonomy of native mussels of the Mytilus genus. Analysing 54 SNP markers, we show the genetic species composition and admixture in the hybrid zone between M. chilensis and M. platensis in the southern end of South America. Bayesian, non-Bayesian clustering and re-assignment algorithms showed that the natural hybrid zone between M. chilensis and M. platensis in the Strait of Magellan, Isla Grande de Tierra del Fuego and the Falkland Islands shows clinal architecture. The hybrid zone can be divided into three different areas: the first one is on the Atlantic coast where only pure M. platensis and hybrid were found. In the second one, inside the Strait of Magellan, pure individuals of both species and mussels with variable degrees of hybridisation coexist. In the last area at the Strait in front of Punta Arenas City, fjords on the Isla Grande de Tierra del Fuego, and at the Beagle Channel, only M. chilensis and a low number of hybrids were found. According to the proportion of hybrids, bays with protected conditions away from strong currents would give better conditions for hybridisation. We do not find evidence of any other mussel species such as M. edulis, M. galloprovincialis, M. planulatus or M. trossulus in the zone.

Cenozoic subsidence‐driving mechanisms in the southernmost Patagonian basins of Tierra del Fuego and SW Atlantic

AbstractForeland basins are ideal laboratories to examine and quantify forces that contribute to Earth's topography. The interaction of these driving mechanisms (atmospheric, lithospheric and asthenospheric) affects the accumulation and preservation of strata in marine or terrestrial depocentres. For foreland basins that cover thousands of kilometres along orogens, geodynamic processes or lithospheric structure might differ and/or overlap differently along or across strike. The Magallanes‐Austral basin in the southernmost Patagonia serves as a good analogue to analyse the interactions between subcrustal forces and foreland sedimentation. While to the northern part of southern Patagonia, Cenozoic basins were predominantly terrigenous and above sea level; at the southernmost end of Patagonia, sedimentation in the island of Tierra del Fuego was mostly submarine. We analysed in this contribution the southernmost foreland of Patagonia by combining backstripping with reconstruction of flexural and dynamic subsidence. These results were compared with terrestrial records exposed further north of southern Patagonia. We found that, in addition to crustal contributions (as deformation and sedimentation), subcrustal forces are required to accommodate the proximal and distal foreland strata and explain the palaeoenvironmental and subsidence discrepancies that resulted after our analysis. When our models are compared with dynamic topographic curves, strong correlations are observed during the Palaeogene, whereas strong topographic differences occurred in the Neogene. Dynamic topography models in the Neogene have reproduced clear uplift, whereas our residual topography results show equilibrium (close to the orogen) to subsidence values (to the distal foreland). We propose that changes in the lithospheric mantle had to work together with the rest of the tectonics and dynamic forces to match 1‐D backstripping and flexural curves. This suggests that foreland basins in southern Patagonia were controlled differently along strike the southern Andes and that crustal deformation, asthenospheric flows and a heterogeneous lithospheric mantle structure affected the Cenozoic basin evolution.

Environmental evolution of western Tierra del Fuego (∼54°S) since ice-free conditions and its zonal/hemispheric implications

By virtue of its position adjacent to the Drake Passage, Tierra del Fuego in South America allows examining the vegetation and environmental history of the southernmost continental landmass outside Antarctica, and the evolution of the Southern Westerly Winds-Southern Ocean (SWW–SO) coupled system since the Last Glacial Maximum (LGM). For that purpose, we studied sediment cores from Lago Charquito, a small closed-basin lake in central-west Tierra del Fuego with a continuous lacustrine record since ∼17.3 ka. Ice-free conditions at the site imply a ∼70 km retreat of the Bahía Inútil glacier lobe from its LGM position during a ∼800-year interval, a trend that continued until its disappearance ∼100 km upstream from L. Charquito, ∼800 years later. Our palynological data show an open landscape dominated by cold-tolerant shrubs and herbs between ∼17.3–12.9 ka, with increases in precipitation of SWW origin at ∼16.3 ka, ∼14.7 ka, between ∼8.7–7.6 ka, and after ∼6.8 ka. Warming at ∼12.9 ka initiated an abrupt afforestation trend that stalled during the early Holocene (∼12–8.7 ka) owing to a precipitation decline and wildfires, and later resumed in response to invigorated SWW. We hypothesize that sparse Nothofagus tree populations inhabited the periphery of the Patagonian Ice Sheet (PIS) during the LGM and migrated toward the Andes contemporaneous with glacier recession as temperature rose during the Last Glacial Termination (T1). We posit that besides establishing topographic and climatic barriers for land biota, the PIS enabled the connectivity of cold-tolerant hygrophilous plant populations along a humid fringe adjacent to its land-based perimeter, despite the presumably dry conditions downwind from the eastern PIS margin. Our results suggest that southward shifts or expansion of the SWW toward or beyond Tierra del Fuego enhanced upwelling and ventilation of deep waters in the SO, northward shifts or weakening had the opposite effect. We observe that the time evolution of atmospheric CO2 concentrations, high-latitude air and sea-surface temperatures, and sea level during T1 fall short in explaining the timing and abruptness of the Bahía Inútil glacier lobe collapse, and quite possibly multiple other glacier lobes from the PIS.

Historical account and current knowledge of the southernmost Chiropterofauna in the world: the Magellanic/Fuegian bats

ABSTRACT A depauperate Chiropterofauna consisting of essentially three bat species (the year-round residents Histiotus magellanicus and Myotis chiloensis, and the apparently migratory Lasiurus varius), exists in the challenging cold and windy environment of the Magellanic/Fuegian region, which encompasses territories in Argentina and Chile, both continental and insular. Knowledge of that bat fauna benefitted from earlier explorers and naturalists visiting such southerly and isolated geographical confines, but still lacks a comprehensive scientific study, particularly in face of expected green-energy projects using aerogenerators known to cause bat fatalities elsewhere. Currently, there is a paucity of information on the fine-scale geographic distribution, local abundance, and migration patterns of those bats that needs to be remedied as soon as possible. Our review may aid orienting and focusing such a research program, which should hopefully be binational, on account of the artificial nature of the border between Argentina and Chile in Tierra del Fuego.

Equivalent impacts of logging and beaver activities on aboveground carbon stock loss in the southernmost forest on Earth

The conservation of forest landscapes is crucial for global climate strategies, and the forest in Tierra del Fuego, located in Patagonia, represents the southernmost example on Earth. These ecosystems are critical for Chile’s roadmap toward carbon neutrality. Unfortunately, these ecosystems have been impacted by logging and beaver activities. Currently, the precise contribution of each driver to forest cover and carbon stock loss remains insufficiently quantified, impeding effective policymaking and the implementation of strategies to safeguard and enhance carbon stocks in these ecosystems. In this study, we conducted an assessment of forest carbon stock loss resulting from both logging and beaver activities in Chilean Tierra del Fuego from 1986 to 2019. While beavers have received significant attention for their substantial contribution to forest cover loss (56.1% forest cover, ≈ 1.4 MtC), our findings suggest that logging has nearly equally contributed to carbon stock depletion (43.8% forest cover, ≈ 1.2 MtC). Consequently, the prevailing focus on beavers has obscured the ongoing logging-induced carbon stock loss. The implications of our study highlight the urgency for comprehensive consideration of both drivers in Chile’s climate strategy to fulfill the country’s mitigation commitments.

Ecotourism, infrastructures, and the drama of sovereignty on a border island

AbstractThe Ruta 30 scenic road project in Argentine Tierra del Fuego has encountered significant resistance. In this article, we analyze a public hearing convened to assess the road's impacts as an event illuminating the daily dynamics of the region. In this borderland, narratives about sovereignty create a space of liminalities between pasts and futures, centers and peripheries, and living and the dead. In this context, and with Patagonia's expanding conservation and ecotourism frontiers, studying public reflexivity becomes crucial for understanding rapid changes. To this end, we employ Turner's “social drama” concept to analyze the hearing as a performance enacting authorized discourses of experts, policymakers, environmentalists, industry, and workers. We conclude by discussing “liminal governance” in a border territory that transcends neoliberal and sovereign designs, and “impossible opposition,” revealing how the hearing reframed the road conflict as a sovereignty crisis, ultimately mitigating potential disruptions to established settler‐colonial structures.

UAV LiDAR in coastal environments: Archaeological case studies from Tierra del Fuego, Argentina, and Vega, Norway

AbstractLiDAR has become fairly integrated into archaeological practice at a global scale. This has gradually evolved to include UAV LiDAR. Nevertheless, considerable biases remain, including with regard to geographical regions, chronological periods, feature types and environments. At present, few studies of coastal environments exist, despite the fact that LiDAR—and UAV LiDAR in particular—has the obvious advantages of flexibility and time efficiency in such archaeologically rich but logistically challenging environments. In this paper, we compare the results of UAV LiDAR surveys with records from previous ground surveys in two case studies from coastal environments on opposite sides of the globe. Case Study I of shell middens located within approximately 3 km2 around Cambaceres Bay involved the first collection of LiDAR data from Tierra del Fuego, Argentina. Case Study II covered approximately 3 km2 of the island of Vega, Northern Norway, and is among the pioneering LiDAR studies of Mesolithic house pits. The detection success rate was fairly good for Cambaceres—69% of 1240 recorded structures were identified on LiDAR—and above expected for Vega, with 81% of 51 recorded house pits identified on LiDAR. In Cambaceres, the main challenges were dense and low vegetation and identifying small middens. Possible new identifications of archaeological features were made in both areas: subtle depressions interpreted as dwelling foundations in Cambaceres and house pits on Vega. We conclude that UAV LiDAR can contribute to coastal archaeology and that it has added values besides making new identifications, being both flexible and time efficient. An example pertains to the possible identification of a practice that has not previously been proved archaeologically in Tierra del Fuego—more thorough site preparation prior to the construction of the dwellings—which in turn raises new questions.

Presence of Echinococcus granulosussensulato in the endoparasitic fauna of feral dogs in Tierra del Fuego, Argentina.

The feral dog population from Tierra del Fuego (Argentina) has affected provincial sheep production, and is responsible for the decrease of 43% of the sheep stock. In addition, feral dogs preys on the native fauna, especially the guanaco (Lama guanicoe), a species protected by law. Except for some data on the aforementioned impact, very little is known about feral dogs features in this region, such as distribution, abundance, diet, reproduction, health status, among others. Therefore, a descriptive observational study was carried out in the period 2018-2021 in Tierra del Fuego, with the aim to recognize the endoparasitic fauna of these dogs, with emphasis on Echinococcus granulosus sensu lato (s.l.). Feces samples were collected from 83 feral dogs captured in 15 farms, which were evaluated using flotation and sedimentation coproparasitological techniques, and optical microscope observation. These qualitative methods showed that 66.3% of the samples were positive. Nine parasitic forms were found, including eggs of taenids, Toxocara canis and Toxascaris leonina, and Sarcocystis spp. oocysts and Giardia spp. cysts. Samples with more than one parasitic form were also observed, among which the Taenia/Sarcocystis spp. association was the most frequent. For the diagnosis of canine echinococcosis, the detection of Echinococcus spp. antigens by Copro-ELISA and the molecular confirmation by Copro-PCR were performed. The Copro-ELISA test was positive in 10/80 (12.5%) of the samples processed, while 11 samples (13.8%) were positive by Copro-PCR. Their distribution showed that 9 (81.8%) corresponded to farms with sheep farming, and 2 (18.2%) with cattle farming. The presence of E. granulosus s.l. in feral dogs from Tierra del Fuego is the most relevant finding in this study. These results confirm that feral dogs have access to viscera infected with hydatid cysts. However, the intermediate hosts involved (sheep, cattle or guanacos) should be investigated. Its impact on the transmission of cystic echinococcosis in this region should be evaluated, as well as the adequacy of the disease prevention and control actions implemented in Tierra del Fuego should be considered. Finally, the existence of a wild cycle of the disease should be evaluated, in which feral dogs would act as a source of infection for other animals and humans.

Historical Climate Change Dynamics Facilitated Speciation and Hybridization Between Highland and Lowland Species of Baripus Ground Beetles From Patagonia

One of the largest beetles of Patagonia, Baripus (Cardiophthalmus), includes 20 currently described species. Its distribution ranges from the tip of Patagonia, on Tierra del Fuego Island, to isolated patches along the Andes and extra-Andes mountains in northern Patagonia on the Payunia at >3000 m elevation. Here, using RADseq data, evidence is found of mixed ancestry in different lineages. Phylogenetic network reconstruction shows two hybridizing edges between lowland and highland species. Using environmental niche modeling, we show changes in geographic distribution of potential niches of species during the last glacial maximum compared to their present distribution. Increasing potential niche overlap among different species pairs possibly explains how lineages came into secondary contact, supporting the hypothesis of hybridization. In addition, morphological evolution is studied using geometric morphometrics on the network, and evidence of transgressive evolution has been found involving the pronotum shape, as well as highland/lowland habitat preferences. Finally, based on genomics and morphological data and using an integrative coalescent-based species delimitation approach, the separate evolution of two lineages in early stages of speciation is found. Taken together, dynamics of diversification of Baripus beetles in both space and time are discussed.

Magmatic arc evolution during the tectonic closure of the Rocas Verdes basin: insights from Cretaceous–earliest Paleocene intrusive rocks of Navarino Island (55°S), Fuegian Andes

Navarino Island is located in the southernmost part of the Fuegian Andes, south of the Beagle Channel. Its geological record documents the complex tectonic history of Tierra del Fuego, which includes the opening and closure of the Rocas Verdes basin, Cordillera arc collision and subsequent subduction processes. The geology of the island is mostly composed of the Cretaceous Yahgán Formation, a marine metasedimentary sequence, which is intruded by diverse plutons that are mostly exposed on the northwestern tip of the island. We herein present a new dataset that shows the presence of three Cretaceous–earliest Paleocene magmatic suites of active margin magmatism emplaced during the early stage of the Fuegian Andes, which are referred to as (1) the Dientes de Navarino Microdioritic Sills, a suite of pre-tectonic microdioritic sills that formed at c. 101–97 Ma; (2) the Castores Plutonic Complex, a series of pre- to syntectonic gabbroic to tonalitic plutons emplaced at c. 90–87 Ma, and (3) the Samantha Monzonites, a suite of isolated monzonitic to monzodioritic post-tectonic plutons that formed at c. 66–65 Ma. These distinct magmatic episodes are recognized by field observations, geological mapping, petrography and whole-rock geochemistry integrated with amphibole and biotite 40 Ar/ 39 Ar and U–Pb LA-ICP-MS. The geochemical compositions of these rocks are consistent with a continental arc setting that existed during the interval c. 101–65 Ma. Whereas the three pulses spatially overlap in Navarino Island, the arc magmatism shows a migration (or expansion) throughout the Late Cretaceous. The locus of the arc then migrates at c. 68–66 Ma towards the SW. We suggest that this trenchward migration at c. 68–66 Ma may be associated with a change in the subduction angle. The three Cretaceous–earliest Paleocene plutonic pulses recorded in Navarino Island formed during the early stages of development of the Fuegian Andes, and are pre-, syn- and post-tectonic with respect to a major compressional event caused by the collision and obduction of the back-arc Rocas Verdes oceanic floor. Supplementary material: A detailed dataset is available at https://doi.org/10.6084/m9.figshare.c.6675416

Association between bryophytes and seedlings in Nothofagussub‐Antarctic forests

AbstractBryophytes, which include mosses, liverworts and hornworts, indeed play a significant role in the natural dynamics of native forests. They contribute to fundamental ecological processes such as tree regeneration. In this context, the objective was to analyse the association of bryophytes with Nothofagus seedlings, as well as whether the substrates where bryophytes grew influenced bryophyte‐tree seedling association, in sub‐Antarctic forests at two contrasting landscapes (coastal and mountain) of Tierra del Fuego (Argentina), to better understand their impacts on the natural regeneration processes. We hypothesized that bryophytes act as a substrate for seed germination and initial regeneration growth in pure and mixed forests of N. pumilio and N. betuloides, resulting in widespread tree seedlings–bryophyte associations in all landscapes. In each forest and landscape location, 60 transects were established (10 m in length) to evaluate bryophyte cover (by point intercept method) and substrate type (bare soil, decaying wood and litter cover) where they were growing. An adaptation of the relative interaction index (RII) based on tree seedling cover associated with bryophyte species (%) and tree seedling cover in the absence of bryophytes (%) was calculated and analysed to assess competition or facilitation between bryophytes and tree seedlings. Nothofagus pumilio seedlings were less abundant in bryophytes compared to other substrates, suggesting an inhibitory effect on the germination and/or survival of N. pumilio. In contrast, the seedlings of N. betuloides, in both pure and mixed forests, exhibited higher abundance on bryophyte substrates, particularly in mosses at mountain landscape (RII = 0.83 ± 0.08 in litter and 0.62 ± 0.11 in decaying wood). These findings suggest that bryophytes play a facilitating role for N. betuloides seedlings during germination and initial phases of growth, mainly in the mountain. Therefore, their conservation promotes N. betuloides forest continuity, both in pure and mixed structures.

Integration of empirical and modelled data unravels spatiotemporal distribution and connectivity patterns of Fuegian sprat early life stages

The distribution patterns of fish early life stages are critical to recruitment success and closely related to major oceanographic circulation patterns. We explored the spatiotemporal distribution of early life stages of Fuegian sprat Sprattus fuegensis, a key trophic species in the Southwestern Atlantic Ocean (SWAO), in a complex oceanographic setting. Samples were collected during austral spring, summer, and autumn, from 2014 to 2017, across areas with distinct biophysical properties between Tierra del Fuego (TDF) and the marine protected area ‘Namuncurá’ at Burdwood Bank (BB) (ca. 54°S). Results revealed significant seasonal fluctuations in abundance, distribution, and ontogenetic composition across habitats. High egg and early larval abundances at Isla de los Estados (IE) suggest it is an additional spawning ground to those previously identified at TDF and BB. However, only the latter appear to be suitable nursery areas. Particle-tracking simulations based on egg abundance and spawning dates were conducted for the first time using results from a high-resolution hydrodynamic model. Particle transport provides evidence of connectivity between IE and neighbouring areas—enhanced when horizontal diffusivity is incorporated into the model—but not between TDF and BB. Simulated distributions closely resembled empirical patterns from this and other studies, allowing the integration of empirical and modelled data to schematize the species’ dispersal pathways in the study area. These results offer new insights into distribution and connectivity patterns among spawning grounds and highlight the potential use of hydrodynamic models for future assessments of Fuegian sprat and other planktonic species’ dispersal and recruitment in the SWAO.

The Poet Discovers Sources (of the Self ). Adam Zagajewski and Charles Taylor

The article shows Adam Zagajewski’s relationship with Charles Taylor’s thought. The author argues that the poet’s dialogue with the philosopher is not limited to quotations and direct references but is also revealed at a deeper level. Based on Zagajewski’s essays and interviews, the author concludes that the poet studied Sources of the Self and The Ethics of Authenticity, and probably also drew on later works dealing with the condition of religion in a disenchanted world (“A Catholic Modernity?” and A Secular Age). Zagajewski borrowed from Taylor’s historical argument about the genealogy of modern identity. He also alluded to the philosopher’s diagnoses of the Enlightenment-Romantic lineage of modern Europeans and his conviction that the struggle for more demanding forms of spiritual life is preserved. The most direct traces of the conversation with Taylor can be found in the essays from The Defense of Ardor. The author suggests that Zagajewski also alludes to Taylor’s diagnoses in poems (e.g., “Tierra del Fuego”, “Senza flash”, and “The Kingfisher”), in which the motifs of spiritual lobotomy and the epiphanic power of poetry appear.

Biotopes of the intertidal zone in Clarence Island (south of the Strait of Magellan).

The characteristics of the Strait of Magellan promote the formation of unique environments, with diverse habitats and marine organisms. This fragmentation of the landscape generates diverse little-explored ecological associations, especially in the zone of sub-Antarctic islands of the Tierra del Fuego archipelago. One way to address this lack of knowledge is through the biotope characterization methodology, with ecological units composed of the habitat and the communities associated with these environments, obtaining data and information on the dominant and incidental taxonomic groups. This is a good research model to conduct baseline studies in coastal benthic marine environments. A data set in Darwin Core standard is presented of the species that make up the intertidal biotopes of Clarence Island (Tierra del Fuego Archipelago, south of the Strait of Magellan). This includes 50 identified species and the specific coordinates for each sampled location, with a total of 1400 georeferenced records. Mollusks were the most diverse taxon with 21 species, followed by algae (14 species). Sessile organisms such as the barnacles Elminiuskingii and Austromegabalanuspsittacus predominate in these ecosystems, followed by bivalve mollusks such as Choromytiluschorus and Mytiluschilensis, which together with Nacellamagellanica and the alga Hildenbrandia sp. make up more than 50% of the total records. The inclusion of biotope patterns in this study complements the information on benthic marine flora and fauna in the intertidal zone, including new records for the coast in the Clarence Island area, which is within the boundary of the Kawésqar National Park.

Structure and Temporal Variability of the Northern Branch of the Antarctic Circumpolar Current in the Drake Passage

The Antarctic Circumpolar Current plays the key role in the circulation of the Southern Ocean and affects the distribution of heat by the ocean on the global scale. The study of the dynamics and structure of this current becomes especially important in a changing climate. The current is well revealed by satellite altimetry data, which makes possible to study temporal and spatial variability of its structure at different scales. In these studies, the methods for determining the position of individual fronts of the Antarctic Circumpolar Current based on satellite altimetry data become especially important. In this work, we compare various approaches for detection of front locations. The structure of the northernmost branch of the Antarctic Circumpolar Current, the Subantarctic Front, and its spatial and temporal variability was studied based on satellite altimetry data from 1993 to 2020 and the results of a hydrographical section occupied by the R/V “Akademik Mstislav Keldysh” in the northern part of the Drake Passage in February 2020. We selected a 350 km long part of the TOPEX/Poseidon and Jason-1,2,3 satellite altimeter track from Tierra del Fuego to the south for the analysis of the dynamics of the front. Criteria for determining the position of the northern and main branches of the Subantarctic Front are presented based on satellite altimetry data. A long-term shift of the position of the fronts relative to the previously accepted levels of absolute dynamic topography has been found. It was found that the accuracy of determining the position of fronts using fixed values of dynamic topography may decrease with time, in particular due to changes in the mean sea level. A statistically significant long-term trend of sea level rise in the region of the Subantarctic Front was found. This trend is 4 mm/yr for the northern branch and 2.5 mm/yr for the main branch.

Raw Material Consumption Strategies in Holocenic Hunter-Fisher-Gatherer Groups from the South-Eastern Coast of Tierra del Fuego (Argentina): A Use-Wear Perspective.

ABSTRACT Hunter-fisher-gatherer societies who inhabited the south-eastern Atlantic Coast of Isla Grande de Tierra del Fuego (Argentina) exploited a wide range of local raw materials that includes, among others, metamorphic, fine-grained rocks and slates that exhibit different physical properties. The aim of this work is to discuss raw materials procurement and production strategies in relation to tool usage. For that purpose, we studied eight archaeological sites retrieved in the Late Holocene. We will focus on the economic practices that involve lithic raw materials to understand technological organization based on the use-wear method and morpho-technical analysis. The results show that these societies developed a technological strategy that implied the selection of rocks with specific properties for performing different and singular activities. Fine-grained rocks were mainly exploited for manufacturing small retouched tools used for scraping hides whereas metamorphic rhyolites and slates were mostly procured to produce long retouched blanks for sawing hard materials.

Dominance of Phycosiphon incertum vs Zoophycos in shelf environment: example from the transgressive Palermo Aike black shale deposits of the Austral-Magallanes Basin, Argentina

The Zoophycos ichnofacies and its main components, Zoophycos isp., Phycosiphon incertum and Chondrites isp. have been related to marine environments of low energy and oxygen. This situation is very common in shelf environments of the past, the most important oil source rocks and/or unconventional reservoir. The Early Cretaceous Palermo Aike Formation of the Austral-Magallanes Basin (Southern Argentina) records marine sedimentation, composed mainly by black shales, with subordinate fine-grained sandstones, and redeposited tuff, deposited in a shelf environment. This succession is the main source rock and constitute a latent unconventional reservoir of the basin. In this paper we present the sedimentological and ichnological study of two well cores from the Tierra del Fuego area. These cores record the initial stage of the marine transgression, and the development of a distal shelf environment, with an alternation of black shales and, fine-grained tuff sandstones hyperpycnal deposits. The ichnological content that records this transgression shows three different ichnofacies: i) autochthonous Cruziana ichnofacies represented by Thalassinoides isp., Teichichnus isp., Planolites isp., Chondrites isp. and Rizocorallium isp. This trace fossil association is rapidly replaced by ii) Zoophycos ichnofacies represented by Phycosiphon incertum, Chondrites isp., and small Zoophycos isp. Finally, another allochthonous Cruziana ichofacies is observed related to the low-density turbiditic deposits, composed by Thalassinoides isp., Gyrolithes, Teichichnus isp., Scolicia isp. and Haenzchellinia isp. In the Santa Cruz area, a large Zoophycos isp. dominance is observed in the fine-grained deposits, occasionally interbedded with coarser-grained low-density turbiditic deposits with doomed pioneers. In the study area (Tierra del Fuego), on the contrary, a dominance of Phycosiphon incertum is observed instead of Zoophycos isp. which when is present have very poor development in size. This could be due to the fact that low-density turbiditic flows are very frequent in the study area, which generates a very unstable environment that does not allow the development of large Zoophycos isp. This environmental differences between the outcrops of Santa Cruz in the north of the basin and the subsurface study area in Tierra del Fuego may be triggered due to climatic, volcanic, or tectonic allogenic control factors.

Drivers of post-fire Nothofagus antarctica forest recovery in Tierra del Fuego, Argentina

IntroductionLarge wildfires were historically absent in the forests of Tierra del Fuego, southern Argentina. This has changed in recent decades as humans have increased ignition sources, and warmer, drier periods have fueled large, severe wildfires. As a result of its location at an extreme southern latitude, Tierra del Fuego has very low tree species diversity. One of the region's dominant tree species, Nothofagus antarctica, is believed to have traits that may make it resilient to wildfire (e.g., the ability to resprout prolifically).MethodsThis study examined post-fire N. antarctica regeneration across an environmental and time-since-fire gradient. Plots were established in burned areas (n = 160) and unburned controls (n = 32) in and around two wildfires that occurred circa 1940 and in 2019. Seedling/resprout and sapling regeneration densities, as well as site characteristics (e.g., slope) and fire-impacted variables (e.g., distance to mature live trees), were measured.ResultsSeedling and resprout densities were lower in burned plots than in controls, with this trend being exacerbated in the 2019 fire with increasing distance from mature live trees. Regeneration generally occurs in clumps and principally through sprouting from live and top-killed trees, with not all top-killed trees having resprouted. Seedling and resprout densities were most strongly impacted by time since fire, distance to mature live trees and post-fire canopy cover. Sapling densities were modulated by slope, time since fire, and distance to mature live trees.DiscussionDespite lower regeneration densities in recently burned plots and less live basal area and canopy cover in older burned plots compared to unburned controls, burned stands may be on a trajectory to recover pre-fire characteristics, although this recovery is spatially variable. However, full recovery has not occurred 80 years after the 1940's fire. Currently, these burned areas resemble grasslands or savannas. They do not provide the habitat or ecosystem services that denser forests do and may require active restoration to fully recover their pre-fire characteristics.

Variation in the trophic niche and food provisioning between the early and late chick-rearing stages in Magellanic penguins Spheniscus magellanicus at Martillo Island, Tierra del Fuego, Argentina

Variation in the trophic niche and food provisioning between the early and late chick-rearing stages in Magellanic penguins Spheniscus magellanicus at Martillo Island, Tierra del Fuego, Argentina

Beach-gravel armouring response to sea level rise: Case studies from Patagonia and Tierra del Fuego

High-latitude coasts are composed dominantly by coarse-grained sediments derived from Pleistocene glaciations. These inherited composition led to gravel armouring either of beaches or spits. The expectance for the anthropogenic-induced sea-level rise will be therefore attenuated due to this resistance of gravel beaches to migrate onshore. Several examples from the Patagonian and Fuegian coasts are described and analysed. Armouring, migration and cannibalisation of gravel spits should be considered in order to forecast the evolution of these coasts in relation to sea-level rise.