Recent Uplift Research Articles

High-Resolution Genome Assembly and Population Genetic Study of the Endangered Maple Acer pentaphyllum (Sapindaceae): Implications for Conservation Strategies

Abstract Acer pentaphyllum Diels (Sapindaceae), a highly threatened maple endemic to the dry-hot valleys of the Yalong River in western Sichuan, China, represents a valuable resource for horticulture and conservation. This study presents the first chromosomal-scale genome assembly of A. pentaphyllum (~626 Mb, 2n = 26), constructed using PacBio HiFi and Hi-C sequencing technologies. Comparative genomic analyses revealed significant recent genomic changes through rapid amplification of transposable elements, particularly long terminal repeat retrotransposons, coinciding with the dramatic climate change during recent uplift of the Hengduan Mountains. Genes involved in photosynthesis, plant hormone signal transduction, and plant-pathogen interaction showed expansion and/or positive selection, potentially reflecting adaptation to the species’ unique dry-hot valley habitat. Population genomic analysis of 227 individuals from 28 populations revealed low genetic diversity (1.04 ± 0.97 × 10-3) compared to other woody species. Phylogeographic patterns suggest an unexpected upstream colonization along the Yalong River, while Quaternary climate fluctuations drove its continuous lineage diversification and population contraction. Assessment of genetic diversity, inbreeding, and genetic load across populations revealed concerning levels of inbreeding and accumulation of deleterious mutations in small, isolated populations, particularly those at range edges (TKX, CDG, TES). Based on these results, we propose conservation strategies, including the identification of management units and recommendations for genetic rescue. These findings not only facilitate the conservation of A. pentaphyllum but also serve as a valuable resource for future horticultural development and as a model for similar studies on other endangered plant species adapted to extreme environments.

Sierra Negra, Galápagos: A resurgent-block basaltic caldera

Caldera resurgence is rare at mafic volcanoes. Here we consider the well-exposed resurgence at Sierra Negra caldera (Galápagos) to investigate how resurgence develops at a mafic system. Based on topographic and field analysis, the structure of the resurgence consists of an eastward-tilted block bounded by a fault-propagation fold activated by a steep inward-dipping reverse fault with dip decreasing toward the surface. Extension of the uplifted part of the reverse fault results from gravitational instability and is accommodated by horst-and-graben structures over a zone several hundred meters wide. Extension culminates in the main normal fault responsible for the inward tilt of the lava pile, forming a distinctive ridge. The resurgence results from spatially and temporally distinct unrest episodes, promoted by the shallow accumulation of large volumes of magma. Sierra Negra is the first documented example of piecemeal resurgence, as shown by the recent uplift episodes associated with eruptions in 2005 and 2018. The example of Sierra Negra suggests that the formation of resurgent blocks depends on the initial location of the feeding system, with non-centered feeding systems developing asymmetric (trapdoor) blocks. Finally, Sierra Negra demonstrates that mafic volcanoes without well-developed rift zones may promote resurgence when reaching a mature stage with significant amounts of cumulates, favoring shallow magma accumulation.

Crustal melting and continent uplift by mafic underplating at convergent boundaries.

The thick crust of the southern Tibetan and central Andean plateaus includes high-conductivity, low-velocity zones ascribed to partial melt. The melt origin and effect on plateau uplift remain speculative, in particular if plateau uplift happens before continental collision. The East Anatolian Plateau (EAP) has experienced similar, more recent uplift but its structure is largely unknown. Here we present an 80 km deep geophysical model across EAP, constrained by seismic receiver functions integrated with interpretation of gravity data and seismic tomographic, magnetotelluric, geothermal, and geochemical models. The results indicate a 20 km thick lower crustal layer and a 10 km thick mid-crustal layer, which both contain pockets of partial melt. We explain plateau uplift by isostatic equilibration following magmatism associated with roll-back and break-off of the Neo-Tethys slab. Our results suggest that crustal thickening by felsic melt and mafic underplate are important for plateau uplift in the EAP, Andes and Tibet.

Recent uplift of Chomolungma enhanced by river drainage piracy

Recent uplift of Chomolungma enhanced by river drainage piracy

Characterization of the active fault deformation zone of the Chegualin Fault in the alluvial plain of southwestern Taiwan

The activity of a creeping active fault poses significant challenges to engineering structures due to surface deformation. Therefore, quantifying the strain concentration caused by an active fault, delineating the extent and location of the Active Fault Deformation Zone (AFDZ), estimating long-term deformation trends, and predicting future deformations are crucial in the field of engineering geology.This study comprehensively integrates multi-timescale analytical methods by incorporating detailed geodetic data, rupture surveys, morphotectonic analysis, geological borehole data, biochronological data, radiocarbon dating, and Holocene uplift rate analysis to identify or confirm the locations of active faults and the long-term evolution trends of active deformation zones. Based on our findings, three active fault planes are identified, with one possibly being the main fault with the highest activity. Furthermore, by comparing long-term deformation rates derived from isochrone lines with short-term deformation rates obtained from leveling, we observe a risk of slip rate deficit. These findings have significant implications for engineering geology. As a general contribution, our study can serve as a site screening strategy for similar locations. Regarding the infrastructure we targeted, we provide critical input parameters for further numerical models (such as the trishear model) to simulate surface deformation, and offer essential design parameters for structures. Considering potential coseismic deformation on the investigated fault, these results are fundamental for future investigations or mitigation plans.

Morphological characteristics and controlling factors of the piedmont fan systems in the Zanskar region, Northwest Himalaya, India

Piedmont fans are prominent geomorphic features formed at the transition between mountain slopes and valley floors. This study investigates the morphology of alluvial fans in the Zanskar Basin (ZB) to uncover the key variables influencing their development and morphodynamics. Utilizing advanced GIS and remote sensing techniques, along with field investigations, we conducted a detailed spatial analysis of 103 alluvial fans along the Doda, Tsarap, and Zanskar rivers. This approach allowed for precise mapping and characterization of these fans within complex depositional settings of ZB, particularly where fans merge into bajadas. Our analysis revealed distinct characteristics for the fans, including Fan Area (FA), Fan Slope (SF), Radius (R), Base Length of Fan (BF), Fan Maximum Entrenchment (FME), and Flow Expansion Angle (FEA). A morphometric analysis was then conducted to evaluate the correlation between the fans and their upstream basins. The linear regression analysis demonstrated both positive and negative correlations between these parameters, highlighting the important role of the upstream basins in controlling sediment delivery to fans. The findings suggest that larger basins contribute to the morphological development of fan systems, with larger, less steep fans forming as a result of greater flows and increased sediment supply from basins with denser drainage networks. Lower values of Mountain Front Sinuosity, Valley Floor Width to Valley Height ratio and Basin Elongation suggest that upstream basins in the ZB are significantly influenced by tectonic forces, resulting in linear mountain fronts, V-shaped valleys and elongated upstream basins. The F-99 fan, in particular, has developed a prominent stepped-fan morphology, attributed to differential uplift, vertical incision, and lateral migration of channels across the fan surface. Along the various fronts of the Zanskar, fan morphology is controlled by a complex interplay of long-term tectonic processes, climate, upstream lithology, and basin characteristics. Tectonic forces, particularly the NW-SE-trending ZSZ/STD and ZCT, exert first-order control on fan morphology by influencing sediment-flux and accommodation space. This influence is evident in tectonically modified landforms such as active mountain fronts, fan terraces, elongated basin shapes, wine-glass valleys and triangular facets, all indicating recent uplift and active tectonics in the region. Our results indicate that ZSZ and ZCT exert significant tectonic control over the geometry and evolution of fans, alongside substantial climatic influences.

Accounting for extinction dynamics unifies the geological and biological histories of Indo-Australian Archipelago.

Biogeographical reconstructions of the Indo-Australian Archipelago (IAA) have suggested a recent spread across the Sunda and Sahul shelves of lineages with diverse origins, which appears to be congruent with a geological history of recent tectonic uplift in the region. However, this scenario is challenged by new geological evidence suggesting that the Sunda shelf was never submerged prior to the Pliocene, casting doubt on the interpretation of recent uplift and the correspondence of evidence from biogeography and geology. A mismatch between geological and biogeographical data may occur if analyses ignore the dynamics of extinct lineages, because this may add uncertainty to the timing and origin of clades in biogeographical reconstructions. We revisit the historical biogeography of multiple IAA taxa and explicitly allow for the possibility of lineage extinction. In contrast to models assuming zero extinction, we find that all of these clades, including plants, invertebrates and vertebrates, have a common and widespread geographic origin, and each has spread and colonized the region much earlier than previously thought. The results for the eight clades re-examined in this article suggest that they diversified and spread during the early Eocene, which helps to unify the geological and biological histories of IAA.

Slab Driven Quaternary Rock‐Uplift and Topographic Evolution in the Northern‐Central Apennines From Linear Inversion of the Drainage System

AbstractInvestigating rock‐uplift variations in time and space provides insights into the processes driving mountain‐belt evolution. The Apennine Mountains of Italy underwent substantial Quaternary rock uplift that shaped the present‐day topography. Here, we present linear river‐profile inversions for 28 catchments draining the eastern flank of the Northern‐Central Apennines to reconstruct rock‐uplift histories. We calibrated these results by estimating an erodibility coefficient (K) from incision rates and catchment‐averaged erosion rates obtained from cosmogenic‐nuclide data, and we tested whether a uniform or variable K produces a rock‐uplift model that satisfactorily fits independent geochronological constraints. We employ a landscape‐evolution model to demonstrate that our inversion results are reliable despite substantial seaward lengthening of the catchments during uplift. Our findings suggest that a rock‐uplift pulse started around 3.0–2.5 Ma, coinciding with the onset of extension in the Apennines, and migrated southward at a rate of ∼90 km/Myr. The highest reconstructed rock‐uplift rates (>1 km/Myr) occur in the region encompassing the highest Apennine massifs. These results are consistent with numerical models and field evidence from other regions exhibiting rapid rock‐uplift pulses and uplift migration related to slab break‐off. Our results support the hypothesis of break‐off of the Adria slab under the central Apennines and its southward propagation during the Quaternary. Moreover, the results suggest a renewed increase in rock‐uplift rates after the Middle Pleistocene along the Adriatic coast, coeval with recent uplift acceleration along the eastern coast of southern Italy in the Apulian foreland.

PETROLEUM GEOLOGY OF THE CENOZOIC SUCCESSION IN THE ZAGROS OF SW IRAN: A SEQUENCE STRATIGRAPHIC APPROACH

The Cenozoic stratigraphy of the Zagros records the ongoing collision between the Arabian and Eurasian Plates and the closure of NeoTethys. A Paleogene NW‐SE trending foreland basin was inherited from a Late Cretaceous precursor. Widespread progradation into the foredeep was a feature of both margins which, allied to ongoing tectonism, had by the late Eocene led to the narrowing and subsequent division of the foredeep into the Lurestan – Khuzestan and Lengeh Troughs, separated by the northward continuation of the rejuvenated Qatar‐Fars Arch. This sub‐division strongly influenced subsequent deposition and the petroleum geology of the area. In addition, the diachronous nature of the Arabian – Eurasian collision led to strong diachroneity in lithostratigraphic units along the length of the Zagros. Hence its petroleum geology is best understood within a regional sequence stratigraphic framework. This study identifies three tectono‐megasequences (TMS 10, TMS 11a, TMS 11b) and multiple depositional sequences.The Cenozoic contains a world class hydrocarbon province with prolific oil reservoirs in the Oligo‐Miocene Asmari Formation sealed by the evaporite‐dominated Gachsaran Formation, mostly contained within giant NW‐SE trending “whaleback” anticlines concentrated in the Dezful Embayment. Reservoirs in the SW are dominantly siliciclastic or comprise mixed siliciclastics and carbonates, whereas those to the east and NE are dominated by fractured carbonates. There remains untested potential in stratigraphic traps, especially in deeperwater sandstone reservoirs deposited along the SW margin of the foredeep.Late Miocene to Pliocene charge to the Asmari reservoirs was mostly from Aptian – Albian Kazhdumi Formation source rocks. In some fields, an additional component was from organic‐rich late Eocene to earliest Oligocene Pabdeh Formation source rocks confined to the narrowing Lurestan – Khuzestan Trough. Where mature, the latter source rock is also a potential unconventional reservoir target, although the prospective area is limited due to recent uplift and erosion. Deeper Jurassic source rocks contributed to the Cheshmeh Khush field in Dezful North. Silurian source rocks charged gas‐bearing structures in the Bandar Abbas region.

Interplay between tectonics and surface processes in the evolution of mountain ranges: Insights from landscape dynamics, uplift, and active deformation of Talesh Mountains (NW Iranian Plateau margin)

Drainage divides are dynamic features of a landscape that migrate over time during the development of river networks. In this study, we focused on the geomorphic response of a landscape to the interaction among tectonics, climate, and lithology in the Talesh Mts. along the northwest of the Iranian Plateau. The footprints of these competing forces have been analyzed by divide stability analysis and applying χ, χQ, and Gilbert metrics. Additionally, we examined the effects of bedrock erodibility on landscape evolution processes by measuring the mechanical rock strength of the lithological units in different sectors of the mountain range. The distribution of the χ values suggests a disequilibrium of the drainage networks across the whole main divide and its tendency to migrate towards the interior of the plateau. In contrast, Gilbert metrics, which focuses on a narrow topographic zone across the divide, suggest that the uppermost divide in the northern and southern Talesh Mts. is stable. Moreover, asymmetry in Gilbert metrics across the central part of the range suggests that the divide might be migrating towards the plateau interior. The possible scenario for the whole divide's behavior is associated with the contrasting erosion rates across the divide. In the northern and southern sectors of the Talesh Mts. range, the erosional wave related to the most recent uplift pulses has not reached the divide yet. Mechanism of topographic rejuvenation is controlled by heterogeneous uplift of strong bedrock units in the northern and southern sectors, and weak bedrock units outcropping in the central sector, initiated topographic rejuvenation largely in the central Talesh Mts. Parallelly, the precipitation has a limited effect in assisting and magnifying the divide mobility, reorganization, and landscape transience. In general, we can infer that divide is in a transient state due to the spatially varying rock uplift and bedrock erodibility.

Crustal block-controlled contrasts in deformation, uplift, and exhumation in the Santa Cruz Mountains, California, USA, imaged through apatite (U-Th)/He thermochronology and 3-D geological modeling

Deformation along strike-slip plate margins often accumulates within structurally partitioned and rheologically heterogeneous crustal blocks within the plate boundary. In these cases, contrasts in the physical properties and state of juxtaposed crustal blocks may play an important role in accommodation of deformation. Near the San Francisco Bay Area, California, USA, the Pacific−North American plate-bounding San Andreas fault bisects the Santa Cruz Mountains (SCM), which host numerous distinct, fault-bounded lithotectonic blocks that surround the San Andreas fault zone. In the SCM, a restraining bend in the San Andreas fault (the SCM bend) caused recent uplift of the mountain range since ca. 4 Ma. To understand how rheologic heterogeneity within a complex fault zone might influence deformation, we quantified plausible bounds on deformation and uplift across two adjacent SCM lithotectonic blocks on the Pacific Plate whose stratigraphic and tectonic histories differ. This was accomplished by combining 31 new apatite (U-Th)/He ages with existing thermochronological datasets to constrain exhumation of these two blocks. Additionally, surface exposures of the latest Miocene to late Pliocene Purisima Formation interpreted in 18 structural cross sections spanning the SCM allowed construction and restoration of Pliocene deformation in a three-dimensional geologic model. We found that rock uplift and deformation concentrated within individual Pacific Plate lithotectonic blocks in the SCM. Since 4 Ma, maximum principal strain computed for the more deformed block adjacent to the fault exceeded that computed for the less deformed block by at least 375%, and cumulative uplift has been more spatially extensive and higher in magnitude. We attribute the difference in uplift and deformation between the two blocks primarily to contrasts in lithotectonic structure, which resulted from diverging geologic histories along the evolving plate boundary.

Late Quaternary tectono‐geomorphological investigations of Zanskar Basin, NW Himalaya, India, using geospatial techniques

AbstractGeospatial techniques play a crucial role in geomorphic studies, particularly in the challenging terrains like mountainous regions, inaccessible areas and densely vegetated landscapes, where geomorphic features cannot be recorded easily. Tectono‐geomorphologic observations provide important clues regarding the landscape evolution, morpho‐dynamics and ongoing tectonism of the region. The present study has been carried out in the Zanskar Basin (ZB), located to the south of the Indus Tsangpo Suture Zone (ITSZ), in the hinterland of the NW Himalaya. This study has been carried out to assess and evaluate active tectonics by employing tectono‐geomorphic analysis, dynamics in drainage networks, geomorphological field observations and the Geographic Information System (GIS) environment. High‐resolution satellite images, topographic maps and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) were used to generate primary data sets, which were corroborated with field investigations for valid inferences. The geometry of the ZB suggests that continuous tectonic activity exerts first‐order control on the overall shape, size and structure of the ZB. This first‐order response is clearly reflected in the landforms modified by tectonic processes, namely, linear mountain fronts, elongated shape and tilting of the basin, braided and meandering river courses and lower stream length gradient index values in hard rock terrain. The ZB exhibits several eye‐catching geomorphic features, such as well‐defined triangular facets with wide base lengths and wine‐glass valleys with small outlets along the footwall block of the Zanskar Shear Zone/South Tibetan Detachment System (ZSZ/STDS), as well as the presence of wind gaps, water gaps, bedrock incision, incised and entrenched valleys, narrow gorges and a high incision rate inferring active tectonics and recent uplift in the region. In addition, the existence of uplifted river terraces, as well as the stepped morphology of fans and strath terraces, suggests that the region is experiencing recent activity and ongoing tectonic uplift. These modified geomorphic characteristics suggest that the hinterland, which is part of the NW Himalaya, is tectonically quite active and has experienced a differential rate of tectonics during its evolution. The quantified geomorphic indices and their relations with the tectonics, climate and erosion activity infer that the basin geometry is mostly controlled by the ZSZ/STDS that dips 20°–70° NE, the south‐dipping Zanskar Counter Thrust (ZCT) and other local tectonic elements like the Choksti Thrust (CT), Stondgey Thrust, Zangla Thrust and tectonic structures. The synergised results of quantified geomorphic indices and tectono‐geomorphic evidence in the ZB strongly indicate that both the past and ongoing tectonism have significantly shaped and modified geomorphology of the ZB.

Climate heterogeneity shapes phylogeographic pattern of Hippophae gyantsensis (Elaeagnaceae) in the east Himalaya-Hengduan Mountains.

The interaction of recent orographic uplift and climate heterogeneity acted as a key role in the East Himalaya-Hengduan Mountains (EHHM) has been reported in many studies. However, how exactly the interaction promotes clade diversification remains poorly understood. In this study, we both used the chloroplast trnT-trnF region and 11 nuclear microsatellite loci to investigate the phylogeographic structure and population dynamics of Hippophae gyantsensis and estimate what role geological barriers or ecological factors play in the spatial genetic structure. The results showed that this species had a strong east-west phylogeographic structure, with several mixed populations identified from microsatellite data in central location. The intraspecies divergence time was estimated to be about 3.59 Ma, corresponding well with the recent uplift of the Tibetan Plateau. Between the two lineages, there was significant climatic differentiation without geographic barriers. High consistency between lineage divergence, climatic heterogeneity, and Qingzang Movement demonstrated that climatic heterogeneity but not geographic isolation drives the divergence of H. gyantsensis, and the recent regional uplift of the QTP, as the Himalayas, creates heterogeneous climates by affecting the flow of the Indian monsoon. The east group of H. gyantsensis experienced population expansion c. 0.12 Ma, closely associated with the last interglacial interval. Subsequently, a genetic admixture event between east and west groups happened at 26.90 ka, a period corresponding to the warm inter-glaciation again. These findings highlight the importance of the Quaternary climatic fluctuations in the recent evolutionary history of H. gyantsensis. Our study will improve the understanding of the history and mechanisms of biodiversity accumulation in the EHHM region.

Impact assessment caused by bradyseism phenomena in the Campi Flegrei area

Campi Flegrei (Italy) is among the areas with the greatest volcanic explosive risk in the world due to the dangerousness of the expected hazards, the high exposed value (about 500,000 people will be evacuated during the “alarm phase”), and the vulnerability of the urban settlements under the effect of the volcanic phenomena. The last two dramatic bradyseism phases occurred in 1969–1972 and 1982–1984 when Pozzuoli town was affected by rapid ground inflation, which brought an overall higher level of about 3.5 m and caused numerous earthquakes (M ≤ 4.2), with severe damage to buildings. During 1984, the seismicity was intense, with 33 events with 0.5 < M ≤ 3 and six with 3 < M ≤ 3.8. Subsequently, the Campi Flegrei caldera was characterized by general subsidence for about 20 years until 2005, when a new inflation period started and is still ongoing (∼1 m). The areal distribution of the recent uplift is characterized by the maximum vertical displacement in the town of Pozzuoli, with a radial decrease from the caldera center outwards. The need to better understand Campi Flegrei volcanic activity is fundamental to protecting the population from hazards linked to explosive volcanic eruptions and understanding the role of seismicity as a possible precursor of a potential eruption. In this perspective, as part of the activities of the PLINIVS Study Centre (Centre of Competence of Italian Civil Protection Department for Volcanic Risk), the authors developed a procedure, implemented in a web application, that relates the monitoring of the ground deformation with the behavior of buildings to evaluate the level of progressive damage to the ordinary Phlegraean buildings due to bradyseism in near real time. This study describes the models adopted for the three impact/risk factors (hazard, exposure, and vulnerability) used to estimate building damage.

Structure and petroleum systems of the Eastern Carpathians, Romania

The Eastern Carpathian fold and thrust belt of Romania is one of the oldest oil and gas producing areas in the world. Numerous fields have been discovered in this region since the 1850s, however, their distribution is irregular with most of them clustered in the Moinesti area. Our analysis suggests that although aspects of hydrocarbon generation, reservoir presence and quality are rather similar along the strike of the entire thrust belt, recent uplift and erosional unroofing of the Carpathians ultimately controlled the preservation of oil and gas fields. Areas with the highest amount of exhumation and associated trap breaching, seem to have suffered more intense deformation due to late inversion, which in turn, reflects the rheology of the various basement units of the East European Margin underlying the Carpathians.

Recent Uplift Characteristics of the Southeast Tibetan Plateau, an Analysis Based on Fluvial Indices

The southeastern Tibetan Plateau (SETP) is well known for its large strike–slip faults with high slip rates and a high potential for seismic hazards. However, little is known about its thrust faults and associated seismic hazards, even though they can produce devastating earthquakes despite their relatively low slip rate. Here we investigated the thrust faults and the recent tectonic uplift pattern in the SETP on a regional scale by combining geomorphic analysis and geodetic data. We quantify the potential differential uplift in the SETP recorded in the long-term landscape evolution with geomorphic indices and compare them with differential uplift derived from decadal leveling data and millennial-scale fluvial terrace incision rates. The results show that the northwest of the SETP underwent higher uplift rates compared to its southeast areas, which is in agreement with the GPS-based leveling. Essentially, the geomorphic indices build two value ranges that are spatially clustered and separated by the Muli thrust fault system, a transverse fault system, which is orientated oblique/perpendicular to the large strike–slip fault. The geomorphic indices indicating rapid uplift rates spatially correspond with high rates derived from leveling data on the northwest side of the Muli thrust fault. The Muli thrust fault, therefore, acted as an important topographic and tectonic boundary absorbing partial southeast crustal movement. Hence, further detailed studies, such as seismological investigations, are suggested to be conducted on the Muli fault for seismic hazards evaluation.

Landslides and predisposing factors of the Southern Apennines, Italy

ABSTRACT The Fiumarella di Corleto drainage basin is an emblematic sector of the southern Apennine thrust belt in the Basilicata region (Southern Italy), which is strongly affected by landslides. Landslides both affect the urban area and the facilities related to hydrocarbon exploitation, such as the pipelines and oil wells connected with the oil centre located just outside the eastern border of the study area. Based on a detailed field survey, supported by stereoscopic analysis, a landslide inventory map has been realized, which also reports the associated processes and landforms. The relationships between the different types of landslides and the various predisposing factors like outcropping lithologies, slopes steepness, slope exposition and land use have been also investigated. The acquired data relate to a geologically complex area of the southern Apennines subject to recent uplift and represent a fundamental contribution useful for the correct management of the territory.

Soil organic matter accumulation before, during, and after the last glacial maximum in Byers Peninsula, Maritime Antarctica

Organic matter is incorporated into soil by biological activity, and its preservation depends on composition and organic-mineral interactions. Frost activity, dry and cold climate, and glacial retreat-advance dynamics complexify soil organic matter storage in Antarctica. Byers Peninsula is the largest ice-free area in Antarctica and hosts a high diversity of vegetable and animal species. We hypothesize that (i) the SOM in the Byers Peninsula may reveal a distinct composition due to the antiquity of the ice-free areas not entirely obliterated by the advancing glaciers during the LGM; and (ii) the advancing ice caps at Byers allowed the accumulation of organic carbon at sheltered points of the Peninsula. Thus, the objectives of this work were: i) to characterize physically and chemically selected soils at Byers Peninsula, with emphasis on organic C and N stocks in different soil types, and ii) SOM dating of representative soil profiles. Thirteen soil profiles were dug, described, and classified. The plant species present at each site were identified. Chemical and physical attributes were determined. The C and N contents, δ13C and δ15N ratio isotopes were determined in the SOM physical size-fractionated particles. The C and N stocks were calculated for each SOM fraction. The deepest horizon of six soil profiles were dated by the 14C method.. Soils from Byers Peninsula showed a diverse and varied biochemical nature of SOM, resulting in varying content of C and N. The δ13C weighted mean of the SOM reflects the dominant vegetation type present in each sampling location, except for pre-Holocene soils and soils influenced by ornithogenesis. The highest organic C and N pools were recorded at subsurface horizons and attributed to the organo-mineral association fraction in upper platforms. For all soil groups, there was a significant overlap of δ13C and enrichment of δ15N in all fractions of SOM, requiring the combination of these two signatures to identify possible sources of contribution to SOM in this environment. The oldest soils, subjected to early-mid Holocene uplift, revealed an endolithic signature of pre-LGM age, the first recorded in Maritime Antarctica to this day. This first pre-LGM SOC record can indicate the initial modern colonization of Maritime Antarctica and suggests that ice caps advance during LGM was limited. Soils formed during and after the LGM in low platforms have a lacustrine signature indicating an influence of snowmelt, ice thawing, and permafrost degradation in selecting hygrophilous species. Soils formed in raised beaches have the lowest organic C and N stocks, and the isotopic composition of SOM indicates ancient ornithogenic influence.

A Multigene Phylogeny of Native American Hawkweeds (Hieracium Subgen. Chionoracium, Cichorieae, Asteraceae): Origin, Speciation Patterns, and Migration Routes.

Native American hawkweeds are mainly mountainous species that are distributed all over the New World. They are severely understudied with respect to their origin, colonization of the vast distribution area, and species relationships. Here, we attempt to reconstruct the evolutionary history of the group by applying seven molecular markers (plastid, nuclear ribosomal and low-copy genes). Phylogenetic analyses revealed that Chionoracium is a subgenus of the mainly Eurasian genus Hieracium, which originated from eastern European hawkweeds about 1.58–2.24 million years ago. Plastid DNA suggested a single origin of all Chionoracium species. They colonized the New World via Beringia and formed several distinct lineages in North America. Via one Central American lineage, the group colonized South America and radiated into more than a hundred species within about 0.8 million years, long after the closure of the Isthmus of Panama and the most recent uplift of the Andes. Despite some incongruences shown by different markers, most of them revealed the same crown groups of closely related taxa, which were, however, largely in conflict with traditional sectional classifications. We provide a basic framework for further elucidation of speciation patterns. A thorough taxonomic revision of Hieracium subgen. Chionoracium is recommended.

Controls on Timing of Hydrothermal Fluid Flow in South-Central Kansas, North-Central Oklahoma, and the Tri-State Mineral District

Paleozoic sedimentary rocks in the southern midcontinent of the United States have been affected by multiple events of deformation and fluid flow, resulting in petroleum migration, thermal alteration, Mississippi Valley-type mineralization, and a complex diagenetic history. This record is a hidden history of how cratonal settings respond to tectonic and non-tectonic drivers. The aim of this contribution is to better understand the controls on fluid migration in Paleozoic strata to evaluate whether hydrothermal activity is forced by tectonic or non-tectonic processes. This paper summarizes and vets the distribution of published dates related to thermal events in the southern midcontinent. In addition, we present new U-Pb dates obtained by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) on calcite cements that were formed from hydrothermal fluids. These are from three samples from the Berexco Wellington KGS 1-32 core in Sumner County, Kansas; an ore sample from the Tri-State Mineral District, Neck City, Missouri; and a core sample from the Blackbird 4-33 well in Osage County, Oklahoma. Previous studies of these calcite samples provided evidence for hydrothermal fluid flow, with one of the Wellington samples possibly recording vertical hydrothermal fluid flow out of the basement. The sample from the Tri-State Mineral District (Missouri) yields a mid-Cretaceous age of 115.6±3.1 Ma. This age falls into the timing of the Sevier Orogeny along the west coast and the development of its foreland basin in the midcontinent. Calcites from the Mississippian interval in the Wellington KGS 1-32 core yield dates of 305±10.5 Ma and 305.1±9.1 Ma. Calcite in Mississippian strata from the Blackbird 4-33 core yields a date of 308.6±2.5 Ma. These dates from Mississippian calcite cements indicate hydrothermal fluid flow in the Late Pennsylvanian that coincides with the timing of the Marathon-Ouachita Orogeny or the Ancestral Rocky Mountains Orogeny. A calcite sample from the Ordovician Arbuckle Group from the Berexco Wellington KGS 1-32 core yielded an age of 5.6±1.6 Ma, coinciding with a time after high elevation uplift of the Rocky Mountains was already far advanced. We propose that this hydrothermal fluid flow may have been associated with increased meteoric recharge and increased regional fluid pressure in a basement aquifer that activated local seismic events far into the continental interior. The distribution of ages of hydrothermal fluid flow confirms a syntectonic driver during the Ouachita Orogeny and Ancestral Rocky Mountains Orogeny deformation. Continuation of hydrothermal fluid flow well into the Permian and tailing off early in the Triassic indicates a post-tectonic driver, where uplifted areas continued to provide the recharge from gravity-driven fluid flow, until the mountains were mostly beveled by the early part of the Triassic. A dearth of Triassic and Jurassic hydrothermal events suggests Gulf of Mexico rifting and extension were less important. Rejuvenation of hydrothermal fluid flow in the Cretaceous and continuing into the Paleogene indicates that elevation and regional flexure from both the Sevier and Laramide events continued to drive hydrothermal fluid flow far from the main sites of mountainous uplift and deformation. Finally, hydrothermal fluid flow associated with more recent uplift of the Rocky Mountains may have been activated by recharge events that pressurized a regional basement aquifer and triggered seismic activity.