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Geological map of the Antarctic Peninsula showing the distribution of the principal geological units, modified from Burton-Johnson and Riley (2015). The islands of Livingston, Snow, Low, Adelaide and Alexander are indicated by shaded areas with black dotted perimeter. AP, Antarctic Peninsula; EPLSZ, Eastern Palmer Land Shear Zone (from Vaughan and Storey 2000). Larsen Basin is demarked (Del Valle et al. 1992; Hathway 2000).
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This paper addresses the Jurassic-Cretaceous stratigraphic evolution of fore-arc deposits exposed along the west coast of the northern Antarctic Peninsula. In the South Shetland Islands, Upper Jurassic deep-marine sediments are uncomformably overlain by a Lower Cretaceous volcaniclastic sequence that crops out on Livingston, Snow and Low islands. U...
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... sedimentary and volcanic successions are widely exposed along the Pacific coastal areas of the Antarctic Peninsula ( Figure 1). They exhibit geological evidence of both tectonic and global sea-level changes, notably recorded in the western flank of the northern Antarctic Peninsula by the emergence of submarine marginal basins as part of a continental island volcanic arc (e.g. ...
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... et al. 1995;Torres et al. 1997Torres et al. , 2015Falcon-Lang and Cantrill 2001;Leppe et al. 2007). Relevant lithostratigraphic units and intrusive rocks are exposed in the archipelago of the South Shetland Islands and in southernmost Adelaide and Alexander islands (Figure 1, e.g. Hathway and Lomas 1998;Riley et al. 2012;Bastias and Hervé 2013). ...
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... and Jokat 2006) and the development of the Larsen basin (e.g. Hathway ), whose sedimentary fill is exposed along the eastern flank of the peninsula (Figure 1). The pre-Cretaceous geology of the northwestern Antarctic Peninsula comprises Permian-Triassic metaturbidites of the Trinity Peninsula Group (e.g. ...
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... published stratigraphy of these rocks is summarized below in this Section. Further south, on Adelaide and Alexander islands (Figure 1), similar rocks are exposed that will also be considered to assess possible correlation with the units of the Byers Basin. ...
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... fore-arc units are also exposed further south of the South Shetland Islands, in Adelaide Island (e.g. Riley et al. 2012, Figure 1) and Alexander Island (e.g. Butterworth et al. 1988, Figure 1). ...
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... et al. 2012, Figure 1) and Alexander Island (e.g. Butterworth et al. 1988, Figure 1). Below we review the similarities and differences of these deposits relative to those of the Byers Basin. ...
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... Island lies off the west coast of Antarctic Peninsula, 150 km south of Low Island (Figure 1). Riley et al. (2012) revised the Mesozoic-early Cenozoic lithostratigraphy of Adelaide Island on the basis of geological mapping and U-Pb geochronology. ...
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The early Mesozoic extensional processes recognized in SW Gondwana have been related to a supercontinent precursor break-up phase, the gravitational collapse of a late Paleozoic orogen, changes in subduction dynamics or the impact of a thermal anomaly. However, intraplate extension is still lacking accurate temporal constraints for the area devoid...
The LeMay Group accretionary complex of Alexander Island (Antarctic Peninsula) comprises a 4 km thick succession of variably deformed turbidites associated with thrust slices of ocean floor basalts. The depositional age and provenance of the succession is uncertain with estimates ranging from Carboniferous to Cretaceous. The accretion history is al...
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... The Antarctic Peninsula is the largest continental fragment in West Antarctica and the southern Gondwana collage, and contains several major sedimentary basins that formed along the Pacific margin of Gondwana prior to and during continental breakup. Due to its well-developed accretionary, forearc, magmatic-arc, and back-arc sequences, the Antarctic Peninsula was initially interpreted as an autochthonous contiguous magmatic arc that formed in response to subduction of Paleo-Pacific oceanic lithosphere beneath southern Gondwana during the Mesozoic and Cenozoic (Bastias et al., 2020;Castillo et al., 2020Castillo et al., , 2017Castillo et al., , 2016Nelson and Cottle, 2017;Bradshaw et al., 2012;Fanning et al., 2011;Barbeau et al., 2010;Vaughan and Storey, 2000;Birkenmajer et al., 1997;Birkenmajer, 1992;Loske et al., 1988;Miller, 1983;Harrison et al., 1979;Halpern, 1965). However, recent geophysical and geological studies indicate that the Antarctic Peninsula is a composite magmatic arc that was accreted to the Gondwanan margin during the Cretaceous. ...
... The geology of Antarctic Peninsula is divided into three domains: west domain, central domain and east domain (Vaughan and Storey, 2000). More recently, the central and east domains are concluded to be the autochthony according to the isotopic composition of Triassic igneous and metamorphic rocks from these domains (Bastias et al., 2020). The northern Antarctic Peninsula, belonging to the east domain, largely consist of low to intermediate grade poorly fossiliferous turbiditic and pelagic metasedimentary rocks which are known generally as the Trinity Peninsula Group in Graham Land (Figure 1a). ...
Geochemical compositions can be used to determine the tectonic setting of sedimentary basins, while where the link of source to sink is no longer preserved, detrital zircon age patterns can aid in resolving the original basin setting. The metasedimentary Legoupil Formation, located at Cape Legoupil and the Schmidt Peninsula, could give a hint for the tectonic evolution of Antarctic Peninsula. In this contribution, we constrain the sedimentary provenance of the Legoupil Formation through geochemistry and detrital zircon U-Pb geochronology. The petrography and geochemical features indicate that the provenance of the Legoupil Formation could be felsic rocks. Detrital zircon grains record a steady supply of Permian and Ordovician material into the Legoupil Formation. The youngest concordant zircon ages of 262 Ma suggest that the depositional time of Legoupil Formation is no older than Late Permian. The detrital zircon age spectrum of Legoupil Formation suggests that the Legoupil Formation sediments should be derived from regional sources endemic to western Gondwana prior to its breakup. Together with the previous studies, geochemistry and detrital zircons reflect an active continental margin tectonic setting and the detrital zircon spectra of Legoupil Formation are similar to the ones deposited in forearc tectonic setting.
... Están rodeadas por una plataforma submarina poco profunda que se extiende entre 40 y 60 km al norte del archipiélago (Fretwell et al., 2010). La historia geológica de la Península Antártica y las ISS está marcada por un margen activo debido a la subducción de la Placa Phoenix bajo la Península, a lo largo del margen suroeste de Gondwana, durante el Paleozoico tardío, el Mesozoico y el Cenozoico (Bastias et al., 2019;Bastías et al., 2023). El archipiélago de las Shetland del Sur está formado por rocas volcánicas y volcanoclásticas de edades mesozoicas y cenozoicas (Bastías et al., 2023). ...
Las playas levantadas constituyen una de las mejores evidencias geomorfológicas que atestiguan el cambio relativo del nivel del mar ligado al retroceso de los glaciares desde la última glaciación. En las Islas Shetland del Sur (Antártida marítima), tales morfologías resultan especialmente abundantes, habiendo sido estudiadas en diferentes épocas, usando distintos métodos y a través de distintas perspectivas. El objetivo general de este trabajo es buscar y clasificar la producción científica sobre las playas levantadas en las Islas Shetland del Sur. Para ello, se exploraron los principales repositorios de publicaciones científicas obteniendo una lista definitiva de 65 trabajos que integran el conocimiento general adquirido desde la década de 1960 hasta la actualidad. Durante este período, los estudios geomorfológicos son los más frecuentes, alcanzando un máximo en la década de 2010, seguidos por investigaciones que emplean métodos geocronológicos para datar las playas levantadas. En la década de 2000 aumentó la cantidad de datos y registros, reflejado en la publicación de artículos de revisión. En la última década (2010-2019), los trabajos muestran un enfoque más multidisciplinario, integrando diversas técnicas de datación, incluyendo el ambiente periglaciar y la teledetección. Se concluye que se ha recopilado una cantidad significativa de conocimiento y datos científicos sobre las playas levantadas en las Islas Shetland del Sur, utilizando diversos enfoques, métodos y análisis.
... western border of Northern, Central and South America), which is arguably continuous from the western Aleutians 10 to the Antarctic Peninsula 11 , with the exception of the San Andreas fault 12 in North America. Although difficult access has partially hindered its understanding and characterisation, a plethora of recent data now permits a more robust characterisation of this Mesozoic-Cenozoic continental margin [13][14][15][16][17][18][19][20][21][22] . The Antarctic Peninsula thus makes an excellent natural laboratory for both testing and revising the dynamics in Cordilleran convergent margins. ...
Radiogenic isotopic compositions of arc magmas are a key tool for studying active margin evolution. They have two isotopic end-members: melts formed mostly from juvenile asthenosphere and melts sourced from evolved continental crust/continental lithospheric mantle. Cordilleran-margins are typically more isotopically juvenile near the trench, and conversely, increasingly evolved landward. However, this model has not been tested on the ~1,500 km long Mesozoic-Cenozoic arc of the Antarctic Peninsula. Here we show that while geochemical compositions remain largely constant, radiogenic isotopes become increasingly juvenile with time. Unlike other continental arcs, there is no association between isotopic composition and spatial distribution. This is attributed to: (i) slow subduction of young oceanic lithosphere, resulting in narrowing of the arc and reduced capacity to incorporate continental crust into melts, and (ii) the Cenozoic decrease in convergence rate, which reduced the friction in the slab-overriding plate interface, allowing the arc melts to increasingly source from young juvenile asthenosphere.
... An age in the range of 75 -65 Ma is likely and supported by Tertairy-age plant fossils from Cape Alexandra (Jefferson, 1980). According to Bastias et al. (2019), the deposition of Adelaide Island, which is located to the west of Jenny Island, documented the shift from deep sea sediment during the Late Jurassic period to shallower sediments and volcanic activity throughout the Cretaceous period ( Figure 4). ...
... Jenny Island lithology, chronostratigraphy, and geology map(Bastias et al., 2019). ...
Antarctica has a unique nature, unspoiled by the fact that it is almost completely covered by ice and there are no human community to influence it. The communities near Chile's southernmost tip, which is around 1200 km away, are the closest to the continent and include research stations belonging to various countries, including Türkiye. Because the stations are so remote from civilization, they must meet the needs of research stations on the mainland, which forces them to operate temporarily or with limited capability. The goal of this research was to explore the mineralogical structure around the Turkish Antarctic Research Station (TARS) in order to meet the station's demands, even if only partially. It is anticipated that these minerals can be exploited in this highly protected region, particularly in wastewater treatment systems for filtration or drinking water filtration, as well as for agricultural purposes to be carried out in unique conditions. Cloudiness, which is the largest weakness of optical satellites, as well as snow-covered regions that prohibit the ground from being seen, were considered in the archive scanning of this satellite, and the image dated 09.01.2020 was determined to be the best suited image. Jenny Island, the nearest land piece to the west, with a distance of 50 km to Horseshoe Island, where the TARS is located, was chosen as the research area among the land parts inside the Hyperion image. ENVI software was used for radiometric and atmospheric corrections of the Hyperion data used in the study. Mineral research was conducted using the Hyperspectral Material Identification (HMI) tool in the Tactical Hyperspectral Operations Resource (THOR) module of the same program. The USGS mineral database was used in the THOR HMI study and the minerals with the best match were selected using the Adaptive Coherence Estimator (ACE) technique. As major minerals, corundum, diaspore, and montmorillonite minerals were detected in the coastal areas north of Jenny Island, albite-plagioclase and microcline-feldspar minerals gave anomalies in the rocky region of the island. Goethite (α-FeO(OH), hematite (Fe2O3), ferrihydrite ((Fe3+)2O3•0.5H2O), lepidocrosite (γ-FeO(OH)), limonite (FeO(OH)·nH2O), rutile (TiO2) and cuprite (Cu2O) minerals were detected in low concentrations.
... The igneous rocks crop out in remote locations that were sampled during two field seasons as part of this study, or samples were provided by the British Antarctic Survey archive and the Byrd Polar and Climate Research Center, USA. We combine our data with previous results from the Antarctic Peninsula (Riley et al. 2001(Riley et al. , 2016(Riley et al. , 2018(Riley et al. , 2020aRyan 2007;Leat et al. 2009;Haase et al. 2012;Bastias 2014Bastias , 2020Bastias et al. 2019Bastias et al. , 2020Bastias et al. , 2021aBurton-Johnson et al. in press). ...
... The Early Cretaceous plutonic record includes a few exposures on the South Shetland Islands (c. 137-109 Ma; Hervé et al. 2006;Bastias et al. 2019) and in SE Palmer Land, where the Lassiter Coast Intrusive Suite is exposed ( Fig. 2a; Rowley et al. 1983;Riley et al. 2018;Burton-Johnson et al. in press). These rocks are mainly tonalite, quartz diorite and granodiorite and crop out over an area of c. 80 000 km 2 ( Fig. 2a; Burton-Johnson et al. in press). ...
... Further north, seven alkali granites, syenogranites, monzogranites and monzodiorites from the west coast of southern Graham Land also yield Early Cretaceous ages that span c. 135-101 Ma, whereas a gabbro yields a Late Cretaceous date of 81 ± 1 Ma (Fig. 2a). The northernmost Cretaceous 206 Pb/ 238 U concordia dates were obtained from three monzogranites and a granodiorite from the South Shetland Islands, which span c. 138-101 Ma, and are consistent with previous age estimates of volcanic and intrusive rocks from that region (Hervé et al. 2006;Bastias 2014;Israel 2015;Bastias et al. 2019). These data show that Early Cretaceous rocks occur extensively along the Antarctic Peninsula from the SE in Palmer Land to the NW in Graham Land, whereas Late Cretaceous plutons are less abundant, and crop out along the west coast of the central and northern Antarctic Peninsula (Fig. 2a). ...
Periods of cessation, resumption and enhanced arc activity are recorded in the Cretaceous igneous rocks of the Antarctic Peninsula. We present new geochronological (LA-ICP-MS zircon U-Pb) analyses of 36 intrusive and volcanic Cretaceous rocks, along with LA-ICP-MS apatite U-Pb analyses (a medium-temperature thermochronometer) of 28 Triassic–Cretaceous igneous rocks of the Antarctic Peninsula. These are complemented by new zircon Hf isotope data along with whole-rock geochemistry and isotope (Nd, Sr and Pb) data. Our results indicate that the Cretaceous igneous rocks of the Antarctic Peninsula have geochemical signatures consistent with a continental arc setting and were formed during the interval ∼140–79 Ma, while the main peak of magmatism occurred during ∼118–110 Ma. Trends in εHft (zircon) combined with elevated heat flow that remagnetised rocks and reset apatite U-Pb ages suggests that Cretaceous magmatism formed within a prevailing extensional setting that was punctuated by periods of compression. A noteworthy compressive period probably occurred during ∼147–128 Ma, triggered by the westward migration of South America during opening of the South Atlantic Ocean. Cretaceous arc rocks that crystallised during ∼140–100 Ma define a belt that extends from southeastern Palmer Land to the west coast of Graham Land. This geographic distribution could be explained by (i) a flat slab with east-dipping subduction of the Phoenix Plate, or (ii) west-dipping subduction of the lithosphere of the Weddell Sea, or (iii) an allochthonous origin for the rocks of Alexander Island. A better understanding of the geological history of the pre-Cretaceous rocks of Alexander Island and the inaccessible area of the southern Weddell Sea is required.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.6089274
... Thus, due to the generalized NE-SW extension throughout southwestern Gondwana from the Middle Triassic to the Late Jurassic (e.g., Vizán et al., 2017), some rotations of blocks were conditioned by the pre-Jurassic structures from NW-SE to NNO-SSE direction (e.g., Uliana and Biddle, 1988). This extension, triggered by the Tethys slab pull (Vizán et al., 2017), and the high rates of subduction of the Phoenix plate beneath Patagonia plate in a southeastward direction (East et al., 2020), caused the migration of the Antarctic Peninsula towards the south and the opening of the Rocas Verdes basin (Bastias et al., 2019;Bastias et al., 2021;Cao et al., 2022;Jordan et al., 2020;Suárez et al., 2019;van de Lagemaat et al., 2021), and the beginning of the extension of the later Weddell Sea (Bastias et al., 2021;Jordan et al., 2020;Riley et al., 2020). Finally, the shear component on the extensional stresses which affected Patagonia ceased around 157 Ma, wich could be related to the end of the Tethys slab pull ( Fig. 8a; Vizán et al., 2017). ...
... The Tethys slab pull would have exerted northeastward extensional stresses in the outer parts of Gondwana (Vizán et al., 2017), which coincide with the northward migration of the continent between 200 Ma and 170 Ma (Fig. 9c). Furthermore, this continental migration between 200 Ma and 170 Ma coincides with the back-arc extension in the Weddell Sea rift system proposed by Jordan et al. (2020) and Riley et al. (2020) and the uncoupling of the Antarctic Peninsula (Bastias et al., 2019;Bastias et al., 2021;Suárez et al., 2019;van de Lagemaat et al., 2021). The apparent rotation of the continent (170-160 Ma) may be related to the combination of different tectonic events: 1) the cessation of the northeastward extensional stresses caused in part by Tethys slab-pull (160 Ma; Vizán et al., 2017), 2) the southward migration of the Antarctic Peninsula (Bastias et al., 2019;Bastias et al., 2021;Suárez et al., 2019;van de Lagemaat et al., 2021), 3) the opening of the Rocas Verdes Basin (Calderón et al., 2016;Cao et al., 2022;Muller et al., 2021;Ronda et al., 2019), and 4) the Weddell Sea rifting system Riley et al., 2020). ...
... Furthermore, this continental migration between 200 Ma and 170 Ma coincides with the back-arc extension in the Weddell Sea rift system proposed by Jordan et al. (2020) and Riley et al. (2020) and the uncoupling of the Antarctic Peninsula (Bastias et al., 2019;Bastias et al., 2021;Suárez et al., 2019;van de Lagemaat et al., 2021). The apparent rotation of the continent (170-160 Ma) may be related to the combination of different tectonic events: 1) the cessation of the northeastward extensional stresses caused in part by Tethys slab-pull (160 Ma; Vizán et al., 2017), 2) the southward migration of the Antarctic Peninsula (Bastias et al., 2019;Bastias et al., 2021;Suárez et al., 2019;van de Lagemaat et al., 2021), 3) the opening of the Rocas Verdes Basin (Calderón et al., 2016;Cao et al., 2022;Muller et al., 2021;Ronda et al., 2019), and 4) the Weddell Sea rifting system Riley et al., 2020). Moreover, these events were controlled by the high rates of subduction of the Phoenix plate (East et al., 2020), which generated the predominance of the extensional stress in the SSW direction (Fig. 9c). ...
This work presents the analysis of paleomagnetic results obtained from four sampling areas of the Jurassic Bahía Laura Complex in the Deseado Massif and their implications on the regional deformation history during the breakup of Gondwana. Paleomagnetic data show cessation of tectonic block rotations about vertical axes around 160 Ma and a change from a transtensional to a mainly extensional tectonic regime. Two biotite samples yielded ⁴⁰Ar³⁹Ar radiometric ages: one from the eastern outcrops of the Chon Aike Formation (plateau age of 184.66 ± 0.55 Ma) and the other from the La Matilde Formation (plateau age of 157.40 ± 0.65 Ma), located at the central part of the Deseado Massif. Finally, an apparent polar wander path (APWP) was calculated for the Jurassic of South America (200 to 140 Ma). This APWP indicates that South America experienced a northward drift between 200 Ma and 170 Ma, a clockwise rotation (~10°) between 170 Ma and 160 Ma, and a westward drift between 160 Ma and 140 Ma. The 170–160 Ma rotation could has been triggered by the combined effects of the uncoupling of the Antarctic Peninsula, the high rates of subduction of the Phoenix plate beneath Patagonia, the opening of the Rocas Verdes basin and the Weddell Sea, and the cessation of the Tethys slab-pull. Furthermore, the calculated APWP for South America does not support a Jurassic massive true polar wander event.
... Active plate movements resulted in the development of an active volcanic arc system along the present day's Antarctic Peninsula, which dominated the biological and geological processes within the associated fore-(i.e., Byers Basin) and back-arc (i. e., Larsen Basin) basins (Artemieva and Thybo, 2020;Bastias et al., 2020;Hathway and Kelley, 2000;Pirrie and Crame, 1995;Smellie et al., 2020;Storey et al., 1996). ...
... The geological, stratigraphic and paleontological properties of the ~3 km thick volcanic and volcano-sedimentary sequence, cropping out mostly around ice-free coasts and on Byers Peninsula, are widely characterized (Chen et al., 2015;Crame et al., 1993;Dochev et al., 2017;Dochev and Pavlishina, 2020;Hathway, 1997;Hathway and Kelley, 2000;Hathway and Lomas, 1998;Hobbs, 1968;Lomas, 1999;Pallàs et al., 1999;Pirrie and Crame, 1995;Smellie et al., 2020Smellie et al., , 1995Smellie et al., , 1984Smellie et al., , 1980Zinsmeister, 1987). Based on paleontological, geochemical and geochronological data the whole sequence formed during the time span of the Kimmeridgian-Tithonian (Late Jurassic) to Coniacian-Maastrichtian (Late Cretaceous) epochs, with significant hiatuses between Late Valanginian -Early Aptian and Aptian -Coniacian (Bastias et al., 2020;Hathway and Lomas, 1998;Machado et al., 2005;Pankhurst et al., 1979;Smellie et al., 2020Smellie et al., , 1996. ...
... The Byers Peninsula occupies the western part of Livingston Island, and comprises ~60 km 2 of essentially ice-free desolate, low relief topography veneered by periglacial debris. Various aspects of the geological, paleontological, and stratigraphical characteristics of the rocks and the basin evolution were previously studied in detail (Bastias et al., 2020;Crame et al., 1993;Hathway, 1997;Hathway and Lomas, 1998;Lomas, 1999;Smellie et al., 1995Smellie et al., , 1984Smellie et al., , 1980. The modern stratigraphic framework unites the exposed Late Jurassic -Early The following lithostratigraphic description are based on the recent research of Hathway and Lomas (1998) and Lomas (1999). ...
Rock samples from the Early to Late Cretaceous marine and non-marine strata of Livingston Island, South Shetland Islands, Antarctica, were studied. Organic matter (OM) originates predominantly from terrestrially-derived organic particles. Mostly highly fragmented plant remains, and locally vitrinite/semifusinite as part of plant compressions/imprints or thin vitrain/fusain lenses, are present. Bulk geochemical results indicate Type III kerogen with poor hydrocarbon generation potential. Tmax and molecular proxies (i.e hopane and sterane isomerization ratios, MPI-1, etc.), together with the local presence of oily droplets, argue for an early oil window maturity, probably caused by regional volcanic activity. In contrast to the results of petrography and Rock-Eval pyrolysis, molecular composition of extractable OM is dominated by short-chain n-alkanes, saturated fatty acids (FAs) and n-alkanols implying a major contribution of autochthonous OM. This contradiction is most likely caused by decomposition of OM from plant tissues, the predominance of wood remains (i.e., xylites) and the low input of FAs from cuticular waxes. The presence of terrestrial OM is indicated by plant wax-derived lipids and resinous compounds. Prominent even carbon number predominance in the short-chain n-alkane range argue for deposition/decomposition under reducing environmental settings, most probably caused by high sedimentation rates and quick burial. Terpenoid biomarker compositions indicate contribution from conifers, whereas input from phytoplankton/algal organic matter is evidenced by C27 steroids, the presence of 4-methyl steranes and dinosterol. Low concentrations of hopanoids and C15 and C17 branched n-FAs argue for limited bacterial input. Only in one sample from Hannah Point, a difference between the δ¹³C values of the short-chain versus long-chain n-alkanes was obtained, arguing for mixed OM sources (i.e., autochthonous input, land plants). The presence of charred organic matter in most of the studied samples, together with the considerable concentrations of combustion-derived PAHs, argue for the common occurrence of wildfires within the terrestrial environments. Despite the active volcanic arc settings, the compound specific carbon and hydrogen isotopes do not record significant changes in climatic/hydrological conditions, although some short-term events cannot be ruled out. Instead, the δ¹³C and δ²H isotopic fractionation is most likely caused by the specific biosynthetic mechanisms of the plants and the global carbon and hydrogen cycles.
... The distribution of ash beds indicates dominating winds and directions to the volcanic sources (Huff et al. 1996;Trela et al. 2017;Badurina et al. 2021). Volcanic ashes carry also valuable, well-ordered in the geological time frame, information about magmatic processes in the areas of their origin (Bastias et al. 2020;Hannon and Huff 2019;Hannon et al. 2020;Huff 2016;Kiipli et al. 2014;Li et al. 2021). The importance of this aspect is increasing with the age of rocks and processes of interest. ...
The present study deals with the possibilities of applying the zircon saturation thermometry, which is based on the equilibrium between the zircon crystals and the melt, to strongly altered volcanic ashes—bentonites. It proposes an alternative to a widely used method of calculating magma temperature from Zr content and major component composition (Boehnke in Chem Geol 351:324–333, 2013), that is not suitable for bentonites, as most of the major components have been largely altered in these rocks. For calculating source magma temperatures in strongly altered volcanic ashes, the exponential function from the Zr (ppm)/Al2O3 (%) ratio with compositional corrections from the TiO2/Al2O3 ratio was found applicable. The idea to use the ratios of these elements is based on the low mobility of these elements in the earth's surface conditions. Temperatures of magma, forming in the partial melting process, are assessed from the bulk rock composition. Pre-eruption temperatures were estimated from the composition of fine fractions of bentonites. The accuracy of the new method was established from comparison with the method by Boehnke et al. (Chem Geol 351:324–333, 2013). The difference between the two methods was mostly less than ± 30° to ± 50°. The comparison with the magma temperature, estimated from the sanidine composition, revealed 13° lower values on average. Although the proposed method for estimating the source magma temperatures is less precise than the method of accounting for detailed rock compositions, it can be used in strongly altered rocks, where other methods are not usable. The new method still enables differentiation between felsic source magmas originating at low or high temperatures. Early Palaeozoic bentonites in the Baltic Basin can be divided, according to the source magma temperatures, into two types: (1) Low temperature (650–790 °C), containing potassium-rich sanidine and abundant biotite (S type), (2) high temperature (770–850 °C) with sodium-rich sanidine and scarce biotite (I type).
... Byers Peninsula is located in the western part of Livingston Island, South Shetland Islands (Figure 1a; Hobbs, 1968). The Byers Group is Late Jurassic to Early Cretaceous in age and constitutes the dominant exposed succession in Byers Peninsula, it was emplaced in a deep marine to continental fore-arc basin setting (Figure 1c; Bastias et al., 2019;Hathway & Lomas, 1998;Smellie et al., 1980). This Group was divided into the following five formations: Anchorage (?Kimmeridgian-Tithonian), President Beaches (Berriasian), Start Hill (late Berriansian), Chester Cone (?latest Berriasian-mid Valanginian), and Cerro Negro (Aptian) (Hathway & Lomas, 1998) (Figure 1c). ...
Understanding the tectonic framework of the Antarctic Peninsula is hindered by a paucity of paleomagnetic data from key locations. In this study, we present paleomagnetic data from the South Shetland Islands, to the northwest of the Antarctic Peninsula, which provides valuable paleoposition constraints on the Western domain of the Antarctic Peninsula. We report a key reliable paleopole (58.1°S, 354.3°E, A95 = 6.3°) from Livingston Island in the South Shetland Islands at ∼102 Ma. Plate reconstruction models from the Early Cretaceous attach the South Shetland Islands to the Pacific margin of southern Patagonia‐Fuegian Andes at ∼140 Ma. The South Shetland Islands then experienced southward translation to its current position to the northwest of the Antarctic Peninsula following counterclockwise rotation during ∼100–90 Ma. A similar counterclockwise rotation has also been identified from southern Patagonia‐Fuegian Andes but is absent in the Antarctic Peninsula, suggesting a direct affinity between the South Shetland Islands and southern Patagonia‐Fuegian Andes. However, the consistent, almost northward Cretaceous paleomagnetic declination in the Antarctic Peninsula, and the near‐synchronous tectonic‐magmatic history between the Antarctic Peninsula and the southern Patagonia‐Fuegian Andes support an autochthonous continental subduction model for most of the Antarctic Peninsula.
... Our new 206 Pb\ \ 238 U zircon concordia ages (LA-ICP-MS) of four volcanic rocks range between 179 ± 1 Ma and 161 ± 1 Ma, while eight intrusions yield ages between 183 ± 1 and 151 ± 1 Ma. These results are combined with 74 U-Pb zircon concordia ages obtained using TIMS, SHRIMP and LA-ICP-MS, and five previous 40 Ar/ 39 Ar plateau dates from Patagonia and the Antarctic Peninsula from previous work (Bastias, 2020;Bastias et al., 2019;Bastias et al., 2020;Calderón et al., 2007;Fanning et al., 1997;Hervé et al., 2007;Leat et al., 2009;Lovecchio et al., 2019;Mukasa and Dalziel, 1996;Navarrete et al., 2019;Pankhurst et al., 2000;Rapela et al., 2005;Riley et al., 2012Riley et al., , 2016. The distribution of ages reveals four main magmatic pulses that collectively span~225-145 Ma (Figs. 2c,d). ...
... Back-arc extension formed oceanic lithosphere in the Rocas Verdes Basin (RVB; Calderón et al., 2007). Coeval deep-marine sedimentary rocks were deposited in the fore-arc and back-arc of the Antarctic Peninsula, which corresponds to the Byers Basin (BB; Bastias et al., 2019) and the Larsen Basin (LB; Hathway, 2000), respectively. of V2-aged arc magmas in the northern Antarctic Peninsula (~173-160 Ma, Fig. 2b), which were coeval with those in eastern Patagonia (Deseado Massif; Fig. 2a), suggests that the Antarctic Peninsula may have migrated south relative to Patagonia during~180-170 Ma (Fig. 6c), which is consistent with several reconstructions (e.g. Ghidella et al., 2002;Grunow, 1993;Hervé et al., 2006;Lawver et al., 1998). ...
Late Triassic – Jurassic igneous rocks of the Antarctic Peninsula and Patagonia provide evidence for the evolution of the margin of southwestern Gondwana. We present new geochronological (LA-ICP-MS zircon UPb dates) analyses of 12 intrusive and volcanic rocks, which are complemented by geochemical and zircon isotopic (Hf) as well as whole rock isotopic (Nd, Sr) data. These are combined with similar analyses of 73 other igneous rocks by previous studies, to constrain the magmatic evolution and Late Triassic – Jurassic tectonic setting. The distribution of crystallisation ages reveals four main magmatic pulses that collectively span ~225–145 Ma, all of which have compositions that are consistent with a continental arc setting. The first episode occurred between ~223–200 Ma, and records active margin magmatism within the Antarctic Peninsula and northern Patagonia, and reveals the presence of a flat-slab that gave rise to magmatism in eastern Patagonia. After a period of magmatic quiescence (~200–188 Ma), the second episode occurred between ~188 and 178 Ma, with a continuation of arc magmatism above a flattened slab. The third episode spanned ~173–160 Ma, and its geographic distribution suggests the slab was steepening, driving magmatism towards the south and west in Patagonia. Finally, the fourth period occurred between ~157 and ~ 145 Ma, during which time magmas were emplaced along the Antarctic Peninsula and western Patagonia, with no evidence for flat-slab subduction. The analysed rocks include the Chon Aike magmatic province, which has been considered to have been influenced by the break-up of Gondwana, via heating associated with the Karoo plume in southern Africa and the active margin in western Patagonia and the Antarctic Peninsula. Our new data and revised compilation now suggest that the Early - Middle Chon Aike Jurassic silicic magmatic province in Patagonia and the Antarctic Peninsula can be entirely accounted by active margin processes. We also show that the final stage of Jurassic magmatism (~157–145 Ma) was coincident with rifting that formed oceanic lithosphere of the Weddell Sea and back-arc extension of the Rocas Verdes Basin, potentially revealing the presence of a triple junction located between southern Patagonia and the northern Antarctic Peninsula that led to the disassembly of southern Gondwana.
