Ancient Highlands Research Articles

Exploring the evidence of Middle Amazonian aquifer sedimentary outburst residues in a Martian chaotic terrain

The quest for past Martian life hinges on locating surface formations linked to ancient habitability. While Mars' surface is considered to have become cryogenic ~3.7 Ga, stable subsurface aquifers persisted long after this transition. Their extensive collapse triggered megafloods ~3.4 Ga, and the resulting outflow channel excavation generated voluminous sediment eroded from the highlands. These materials are considered to have extensively covered the northern lowlands. Here, we show evidence that a lacustrine sedimentary residue within Hydraotes Chaos formed due to regional aquifer upwelling and ponding into an interior basin. Unlike the northern lowland counterparts, its sedimentary makeup likely consists of aquifer-expelled materials, offering a potential window into the nature of Mars' subsurface habitability. Furthermore, the lake’s residue’s estimated age is ~1.1 Ga (~2.3 Ga post-peak aquifer drainage during the Late Hesperian), enhancing the prospects for organic matter preservation. This deposit’s inferred fine-grained composition, coupled with the presence of coexisting mud volcanoes and diapirs, suggest that its source aquifer existed within abundant subsurface mudstones, water ice, and evaporites, forming part of the region’s extremely ancient (~ 4 Ga) highland stratigraphy. Our numerical models suggest that magmatically induced phase segregation within these materials generated enormous water-filled chambers. The meltwater, originating from varying thermally affected mudstone depths, could have potentially harbored diverse biosignatures, which could have become concentrated within the lake’s sedimentary residue. Thus, we propose that Hydraotes Chaos merits priority consideration in future missions aiming to detect Martian biosignatures.

The Geology of Eden Patera, a Type‐Example of Plains Style Caldera Complexes on Mars

AbstractA population of underrecognized volcanic constructs associated with explosive and effusive volcanism is present within Arabia Terra and perhaps throughout the ancient highlands on Mars. These features, termed “plains‐style caldera complexes,” are characterized by 10s‐of‐km wide crustal collapse structures, lava flows, and potential pyroclastic deposits, but without a pronounced central edifice. Vast layered deposits around Eden Patera and throughout Arabia Terra are possibly linked to these explosive volcanisms. Remote sensing‐based morphological and geologic mapping was carried out along with geomorphological and structural analyses, and the application of terrestrial analogs to test the hypothesis that these large‐scale collapse features are controlled by magmatism and volcanic activity. Here, we map the surface geology, structure, and geomorphology of Eden Patera, providing a well‐exposed and documented benchmark for the identification of other plains‐style caldera complexes across the surface of the Martian crust. The unexplored population of explosive process‐dominated volcanic constructs could potentially be an important yet underrecognized aspect of the Martian geologic record.

Sequence sedimentary evolution and reservoir distribution in the third and fourth members of Sinian Dengying Formation, Gaomo area, Sichuan Basin, SW China

Based on comprehensive analysis of cores, thin sections, logging and seismic data, the sequence stratigraphy and sedimentary evolution of the third and fourth members of Sinian Dengying Formation (Deng 3 and Deng 4 members for short) in the Gaomo area of Sichuan Basin were investigated, and the favorable zones for reservoir development in the Deng 3 Member and Deng 4 Member were predicted. (1) Two Type I and one Type II sequence boundaries are identified in the Deng 3 and Deng 4 members. Based on the identified sequence boundaries, the Deng 3 and Deng 4 members can be divided into two third order sequences SQ3 and SQ4, which are well-developed, isochronal and traceable in this area; the SQ3 thins from west to the east, and the SQ4 thins from northwest to southeast. (2) The sedimentary environment from the depositional period of SQ3 to SQ4 has experienced the evolution from mixed platform to rimmed platform, and the platform rimmed system on the west side is characterized by the development of platform margin microbial mound and grain shoal assemblages. The intraplatform area is a restricted platform facies composed of a variety of dolomites, and there are local micro-geomorphic highlands of different scales and scattered intraplatform mounds and shoals. (3) The Deng 4 Member reservoirs, with obvious facies-controlled characteristic, are mainly distributed in the upper part of high-frequency upward shallow cycle and the high-stand systems tract of the third-order sequence vertically, and are more developed in the platform margin belt than in the intraplatform belt, and more developed in the Gaoshiti platform margin belt than in the west Suining platform margin belt on the plane. (4) Three types of favorable reservoir zones of Deng 4 Member have been finely delineated with 3D seismic data; among them, the mound and shoal facies zones developed in the ancient highlands of the intraplatform are the first choice for the next exploration and development of the Deng 4 Member.

China's Chang'e-5 landing site: Geology, stratigraphy, and provenance of materials

China's Chang'e-5 (CE-5) mission, the first lunar sample return mission since 1976, landed at 43.06°N, 51.92°W on Dec. 1, 2020, in Northern Oceanus Procellarum. CE-5 targeted a mare plain (Em4/P58) composed of distinctive young (∼1.6-1.7 Ga) moderate-Ti mare basalts, with elevated Th abundance (inherent or extraneous). Thus, the regolith and rock fragments sampled by CE-5 come from some of the youngest mare basalts on the Moon, near Rima Sharp, and from the center of the globally anomalous Procellarum KREEP Terrane (PKT), hypothesized to be responsible for the generation of the young volcanism. To provide context for the analysis and interpretation of the returned samples and in-situ measurements of the regolith substructure with penetrating radar, we constructed a detailed geologic map and stratigraphic assessment of the site. The stratigraphy consists of ancient highland materials (PKT crust and ejecta from Iridum and Imbrium basins), local silica-rich volcanism, overlain by a sequence of mare basalts, capped with Em4/P58. A ∼4-7 m thick regolith layer developed by post-mare bombardment overlies the Em4/P58 protolith and contains admixed impact ejecta from distant sources, mainly from Harpalus (∼6 wt.%), followed by Copernicus (∼2 wt.%) and Aristarchus (∼1 wt.%). New crater size-frequency measurements of Em4/P58 provide the necessary crater spatial density reference for calibration of the lunar cratering chronology with radiometric ages of the returned samples. The geological map and assessment of regolith provenance indicate that samples returned by CE-5 will address fundamental questions in lunar chronology, thermal evolution, basalt petrogenesis, and the nature of PKT, as well as provide key calibration for lunar and planetary chronologies and remote sensing data.

Dynamic palaeogeographic reconstructions of the Wuchiapingian Stage (Lopingian, Late Permian) for the South China Block

As an important tool in natural resource exploration, palaeogeography provides a portrayal of deep time Earth. The South China Block located in the eastern Palaeotethys includes multiple natural resources (e.g., coal, shale gas, bauxite, etc.) in the Permian, which are well known for their important economic significance. In this paper, data gathered from literature amount to 431 stratigraphic sections of Wuchiapingian age from South China. These data were quantitatively analyzed and dynamically reconstructed in the global context under the revised plate motion model by GPlates software for the first time. A schematic 3-D model was constructed based on the high-resolution reconstructions in this paper, showing two relatively large highlands developed in the South China Block during the Wuchiapingian, including the Kangdian Highland in the west and the Cathaysia Highland in the east and a small Yunkai Highland in the south. A broad platform-dominated depositional system with small uplifts and depressions was developed between these two highlands. These reconstructions show great potential to explore enriched coal seams and shale gas in the peripheral areas of the two ancient highlands in the west and east of the South China Block. Based on the dynamic evolution of this depositional system, South China experienced an overall sea-level rise with frequent secondary transgressions and regressions during the Wuchiapingian. This is in contrast to the widespread continental and evaporite deposits on much of Pangea and its surrounding margins after the end-Guadalupian global regression. Compilation of conodont biostratigraphic data suggest that the temporal and spatial constraints on the unconformity across the Guadalupian-Lopingian boundary (GLB) resulted from Dongwu Uplift movement. The regression began during the Jinogondolella shannoni Zone and ended in the Clarkina leveni Zone, but the response time varies in different localities of South China. These results provide detailed information about sea-level eustacy, tectonic uplift, sedimentary hiatus, resource accumulation and palaeoclimate change from the South China Block during the Wuchiapingian.

A new method for predicting the shale distribution of the Wufeng Formation in the Upper Yangtze Region, China

Taking the Late Ordovician Wufeng Formation (WFF) shale in the Upper Yangtze region as an example, we conducted a lithofacies distribution, thickness quantification, and paleo-topographic reconstruction of the Late Ordovician graptolite zones. Specifically, we focused on the Late Katian Dicellograptus complexus and the Early Hirnantian Metabolograptus extraordinarius within a chronostratigraphic framework, using the Geographic Information System (GIS) and 310 stratigraphic sections (incl. drilling) obtained from the Geobiodiversity Database (GBDB). Reconstruction of the geographic distribution indicates that the WFF and the synchronous sediments in the Upper Yangtze region contain 8 litho-stratigraphic units, which are geographically distributed across 7 provinces/municipalities and do not exhibit significant variations in lithofacies. The black graptolite shale extends in a broad swath from east to west within the basin, while the other lithofacies deposited during the same period are present on the periphery of the basin. All these strata were deposited in a normal neritic epicontinental sea environment, except for the flysch sediments in the southern Hunan area. The thickness reconstruction involves a comparison of three spatial interpolation methods, including Inverse Distance Weighting (IDW), Kriging, and the Radial Basis Function (RBF). Based on a general verification, IDW is considered to be the optimal method since it has the minimum standard deviation and variance. Based on the contours obtained from the IDW model, the WFF black shale is estimated to have an overall area of 0.67 × 106 km2, an average thickness of 6.2 m, and a total volume of 3902 km3. This shale was deposited over a 2.83 Ma period. Therefore, the volume of shale deposited per million years is estimated to be 1379 km3/my and the average thickness of shale deposited per million years is 2.37 m/my. The Hirnantian paleo-water-depth values obtained using 275 sections were used to infer the Late Katian paleo-topography. These results suggest that the Yangtze platform was surrounded by ancient highlands to the west, south, and north, exhibiting a paleo-geographic framework characterized by one uplift and four depressions. This setting blocked water circulation, causing the water to be contained and forming a closed and restricted marine environment, which was one of the major factors controlling the deposition of the organic-rich WFF shale. With the advent of the big data era of geology, the methodology of GIS-based technology is readily exportable to any resource play having spatial distribution pattern. Results can be provided rapidly and efficiently generated from geological data.

Subsurface Sediment Mobilization in the Southern Chryse Planitia on Mars

AbstractThe southern part of the smooth plain of Chryse Planitia on Mars hosts a large population of kilometer‐sized (from ~0.2 to ~20 km) landforms spread over a wide area. Based on the investigation of a small part of this area, Komatsu et al. (2016, https://doi.org/10.1016/j.icarus.2015.12.032) proposed that the edifices may be the result of the subsurface sediment mobilization. We mapped the full extent of these landforms within Chryse Planitia and performed a morphological and spatial analysis in an attempt to further test this hypothesis. We identified a total number of 1,318 of these objects, which we grouped into five different morphological classes. The edifices can be observed over an area of 700,000 km2 near the termini of the large outflow channels, Ares, Simud, and Tiu Valles, with a nonrandom spatial distribution. The features are clustered and anticorrelated to the ancient highlands, which form erosional remnants shaped by the outflow events. This suggests a genetic link between the distribution of the edifices and the presence of the sedimentary deposits on which they are superposed. Such distribution is consistent with the previous notion that subsurface sediment mobilization may be the mechanism for their formation and is less consistent with the alternative igneous volcanic hypothesis. We also propose a scenario in which the large morphologic variability can be explained by variations of the water content within the ascending mud and by variations in the effusion rates. The edifices may represent one of the most prominent fields of sedimentary volcanism detected on Mars.

Mars atmospheric entry guidance for optimal terminal altitude

Maximizing the terminal altitude for Mars atmospheric entry has long been investigated on trajectory design to allow a sufficient timeline margin for subsequent operations and the scientific requirements of exploring Mars ancient highland. The purpose of this paper is to design an onboard Mars atmospheric entry guidance algorithm, which can achieve the optimal terminal altitude at the predetermined terminal flight range. Two important characters that the optimal bank angle profile are revealed in this paper, offering the gateway to the application of the optimal guidance by onboard parameter searching, which will be accomplished by the numerical predictor-corrector strategy. Moreover, suboptimal situations are also investigated considering the performance restriction of reactive control system (RCS). Effectiveness of the proposed guidance algorithm is demonstrated using scenarios of the Mars Science Laboratory (MSL) mission.

Alteration trends and geochemical source region characteristics preserved in the fluviolacustrine sedimentary record of Gale crater, Mars

Abstract The Mars Science Laboratory’s Chemistry and Camera (ChemCam) instrument suite on-board the Curiosity rover has analysed ∼1200 sedimentary targets during the mission up to sol 1482. These targets have included sedimentary rock, diagenetic features (e.g., fracture-associated alteration halos, mineral veins, nodules, and erosion resistant raised ridges), active aeolian fines, soils and float. We have isolated ChemCam geochemical trends relating to diagenetic features and alteration products from those of the sedimentary rock in order to identify the compositional characteristics of Gale crater’s sediment source regions. The effects of grain size variation on sedimentary unit geochemistry have been taken into account by grouping and analysing geological units according to grain size. With obvious diagenetic features removed from the database, and predominately isochemical aqueous alteration inferred for the Mt Sharp Group samples, we propose that source region composition is a stronger source of geochemical change between the Bradbury and Mt Sharp Groups than open-system alteration. Additionally, a lack of correlation between the Chemical Index of Alteration (CIA) values and SiO2, MgO or FeOT indicates that the slight increase in chemical weathering of the Mt Sharp Group sediments was insufficient to overprint sediment source compositional signatures. This has led to the identification of five unique igneous endmember compositions which we hypothesise to have contributed to Gale crater’s stratigraphic record. These endmembers are: (1) a subalkaline basalt, compositionally similar to the tholeiitic Adirondack Class basalts of Gusev crater, and dominant within the finer grained units up to the base of Mt Sharp; (2) a trachybasalt, mostly identified within conglomerate units from the Darwin waypoint to the base of Mt Sharp; (3) a potassium-rich volcanic source, determined from strong potassium enrichment and a high abundance of sanidine that is most dominant in the fluvial sandstones and conglomerates of the Kimberley formation; (4) a highly evolved, silica-rich igneous source that correlates with the presence of tridymite, and is recorded in the lacustrine mudstone of Mt Sharp’s Marias Pass locality; and, (5) a fractionated, relatively SiO2-rich subalkaline basalt, seen to have influenced the composition of mudstone deposited in the lower part of the Mt Sharp Group. Endmembers (1), (2), (3), and (4) have previously been identified at specific waypoints along the rover’s traverse, but we show that their influence extends throughout Gale’s stratigraphic record. The occurrence of detected endmembers is also strongly correlated with stratigraphic position, which suggests changing sediment source regions with time. We conclude that Gale sediment provenances were much more varied than suggested by the largely homogenous, globally-distributed Martian basalt inferred from orbit, showing that complex magmatic assemblages exist within the ancient highland crust surrounding Gale.

Morphological signatures of high-altitude adaptations in the Andean archaeological record: Distinguishing developmental plasticity and natural selection

High-altitude hypoxia is one of many environmental stressors affecting human populations in the highland Andes. Living highland Andeans show adaptive physiological responses to these conditions through both developmental plasticity and natural selection. Given the longevity of human settlement in this region, these same responses ought to have affected ancient Andeans. This paper tests whether developmental plasticity or natural selection best explains the morphological signatures of adaptations to high-altitude hypoxia in ancient highland Andeans. I compare four groups of skeletons: two groups from lowland regions and two groups from high elevations. Previous work shows that the two highland groups have small bodies and voluminous ribs compared with the lowland groups indicating morphological adaptations to high-altitude environments. This paper compares patterns of intrinsic variation and sexual dimorphism in body size, limb lengths, and rib morphology in highland and lowland groups to test if developmental plasticity or natural selection underlies these morphological differences. The four groups share similar patterns of sexual dimorphism and intrinsic variation in body size and limb lengths. The two highland samples show greater degrees of sexual dimorphism in rib morphology than the lowlanders. Patterns of intrinsic variation in rib morphology do not sort by altitude. Both natural selection and developmental plasticity in response to high-altitude hypoxia likely shaped skeletal morphology in ancient highland Andeans.

Thermal effects of impact bombardments on Noachian Mars

Abstract Noachian (prior to ca. 3700 Ma) terranes are the oldest and most heavily cratered landscapes on Mars, with crater densities comparable to the ancient highlands of the Moon and Mercury. Intense early cratering affected Mars by melting and fracturing its crust, draping large areas in impact ejecta, generating regional-scale hydrothermal systems, and increasing atmospheric pressure (and thereby, temperature) to periodically re-start an otherwise moribund hydrological cycle. Post primary-accretionary bombardment scenarios that shaped early Mars can be imagined in two ways: either as a simple exponential decay with an approximately 100 Myr half-life, or as a “sawtooth” timeline characterized by both faster-than-exponential decay from primary accretion and relatively lower total delivered mass. Indications are that a late bombardment spike was superposed on an otherwise broadly monotonic decline subsequent to primary accretion, of which two types are investigated: a classical “Late Heavy Bombardment” (LHB) peak of impactors centered at ca. 3900 Ma that lasted 100 Myr, and a protracted bombardment typified by a sudden increase in impactor flux at ca. 4100–4200 Ma with a correspondingly longer decay time (≤400 Myr). Numerical models for each of the four bombardment scenarios cited above show that the martian crust mostly escaped exogenic melting from bombardment. We find that depending on the chosen scenario, other physical effects of impacts were more important than melt generation. Model output shows that between 10 and 100% of the Noachian surface was covered by impact craters and blanketed in resultant (hot) ejecta. If early Mars was generally arid and cold, impact-induced heating punctuated this surface state by intermittently destabilizing the near-subsurface cryosphere to generate regional-scale hydrothermal systems. Rather than being deleterious to the proclivity of Noachian Mars to host an emergent biosphere, this intense early impact environment instead enhanced the volume and duration of its surface/subsurface geophysical habitable zone.

Hydrological and sedimentary analyses of well-preserved paleofluvial-paleolacustrine systems at Moa Valles, Mars

Moa Valles is a well-preserved, likely Amazonian (younger than 2 Ga old), paleodrainage system that is nearly 300 km long and carved into ancient highland terrains west of Idaeus Fossae. The fluvial system apparently originated from fluidized ejecta blankets, and it consists of a series of dam breach paleolakes with associated fan-shaped sedimentary deposits. The paleolakes are interconnected and drain eastward into Liberta crater, forming a complex and multilobate deltaic deposit exhibiting a well-developed channelized distributary pattern with evidence of switching on the delta plain. A breach area, consisting of three spillover channels, is present in the eastern part of the crater rim. These channels connect the Liberta crater to the eastward portion of the valley system, continuing toward Moa Valles with a complex pattern of anabranching channels that is more than 180 km long. Based on hydrological calculations of infilling and spillover discharges of the Liberta crater lake, the formation of the whole fluvial system is compatible with short to medium (<1000 year) timescales, although the length and morphology of the observed fluvial-lacustrine features suggest long-term periods of activity based on terrestrial analogs. Water for the 300 km long fluvial system may have been primarily sourced by the melting of shallow ice due to the thermal anomaly produced by impact craters. The occurrence of relatively recent (likely Amazonian) hydrological activity, which could have been primarily supported by groundwater replenishment, supports the hypothesis that hydrological activity could have been possible after the Noachian-Hesperian boundary, which is commonly considered as the onset epoch of the present cold-dry climate.

Ages of Globally Distributed Lunar Paleoregoliths and Soils from 3.9 Ga to the Present

This study determines the ages of 191 discrete lunar regolith samples from the Apollo, Luna, and meteorite collections. Model closure ages (for lithified breccias) and appearance ages (for unconsolidated soils) are calculated using the trapped 40Ar and 36Ar abundances of each sample, determined from published Ar data. Model closure ages of regolith breccias span ~3.9 to 0.01 Ga and appearance ages of soils range from ~3.6 to 0.03 Ga; 169 of these ages are published here for the first time, while 22 are recalculated ages. The regolith breccias with the oldest closure ages originate from the ancient highlands and oldest mare surfaces sampled by the Apollo missions. Soils generally have similar ages to each other, regardless of location and collection depth, with most model ages <2.0 Ga. Together, the soils and regolith breccias represent a record of regolith processes over the past 3.9 Ga. The data illustrate that individual landing sites can provide a diversity of ages, which has implications for planning future missions. Differences in maturity between older and younger regolith samples may reflect a change in collisional regimes over time. We note, too, that the closure ages published here are critical data needed for selecting temporally appropriate regolith samples used to decipher the diversity of impactors hitting the lunar surface over time and how the Sun has changed in time.

Mammary immunity of White Park and Highland cattle compared with Brown Swiss and Red Holstein

Mastitis is a frequent disease in modern dairy cows, but ancient cattle breeds seem to be naturally more resistant to it. Primary bovine mammary epithelial cells from the ancient Highland and White Park (n = 5) cattle and the modern dairy breeds Brown Swiss and Red Holstein (n = 6) were non-invasively isolated from milk, cultured, and stimulated with the heat-inactivated mastitis pathogens Escherichia coli and Staphylococcus aureus to compare the innate immune response in vitro. With reverse transcription quantitative polymerase chain reaction (RT-qPCR), the breeds differed in the basal expression of 16 genes. Notably CASP8, CXCL8, Toll-like receptors 2 and 4 (TLR2 and TLR4) expression were higher in the ancient breeds (P &lt; 0.05). In the modern breeds, more genes were regulated after stimulation. Breed differences (P &lt; 0.05) were detected in C3, CASP8, CCL2, CD14, LY96 and transforming growth factor β1 (TGFβ1) regulation. Principal component analysis separated the ancient from the modern breeds in their basal expression, but not after stimulation. ELISA of lactoferrin and serum amyloid A protein revealed breed differences in control and S. aureus treated levels. The immune reaction of ancient breeds seemed less intensive because of a higher basal expression, which has been shown before to be beneficial for the animal. For the first time, the innate immune response of these ancient breeds was studied. Previous evidence of breed and animal variation in innate immunity was confirmed.

Chinamit and Molab: Late Posclassic Highland Maya Precursors of Closed Corporate Community

This article explores the extent to which documentary evidence from the early Colonial period in Guatemala can be used to demonstrate the existance of closed corporate community as an organizing principle of basic Highland Maya socio-cultural units during the Late Postclassic period (ca. AD 1200-1524). Our ability to detect various aspects of closed corporate community among the ancient Highland Maya allows a more ethnographic characterization of Late Postclassic society, particularly at the non-elite level. The existance of closed corporate community as a principle of organization both during the Late Postclassic and today also raises questions of continuity and the extent of cultural change brought about as the results of the Spanish conquest and colonization.

The Resources of Geological Remains in Qilihai and the Discussion on the Technology of Protective Development

The Qilihai wetland locates in the southwest of Ninghe County in Tianjin. It is the core of Tianjin Ancient Seacoast and Swamp Reserve in China. Qilihai has large amount of rare typical geological remains, such as ancient oysters, ancient highlands, and ancient lagoon. Based on the analysis of the geological remains in Qilihai area, the tactics of protection and development were researched in this paper.

The archaeology of deforestation in south coastal Turkey

The Rough Cilicia Archaeological Survey Project investigates landscape transformation as a component to its regional survey of ancient Rough Cilicia (south coastal Turkey opposite Cyprus). Rough Cilicia was celebrated during antiquity for pristine cedar forests that stood between 1500 and 1800 m in altitude along the slopes of the Taurus Mountains. Today along the front range of the Taurus Mountains this forest is completely denuded or otherwise replanted with recent growth in the past 80 years. We employ paleoenvironmental analysis of relic cedar forests in the Taurus Mountains to construct a timeline of anthropogenic disturbances associated with population growth over time and thereby assess the sustainability of ancient forestry practices. To obtain these data, the team recovers pollen and carbon samples from geomorphologic trenches excavated in the cedar zone, tree ring data from dendrochronological survey of the existing forest, and archaeological data from remains of ancient highland settlements. Preliminary results indicate that current perspectives about the timing of deforestation in this region are flawed and that the initial deforestation coincided with regional site abandonment and population decline at the end of antiquity.

Species formation and geographical range evolution in a genus of Central American cloud forest salamanders (Dendrotriton)

AbstractAim Montane Central America offers an ideal system for testing geographical hypotheses of species diversification. We examined how the complex geological history of Nuclear Central America has shaped the diversification of a genus of cloud‐forest‐inhabiting salamanders (Dendrotriton). We applied parametric models of geographical range evolution to determine the predominant mode of species formation within the genus and to test existing hypotheses of geographical species formation in the region.Location Montane cloud forests of Nuclear Central America.Methods We estimated a species tree for Dendrotriton using a multi‐locus DNA sequence data set and several coalescent methods, and performed molecular dating for divergence events within the genus. We then applied the species‐tree estimate to a likelihood‐based time‐stratified model of geographical range evolution, based on current species distributions and available geological information for Central America.Results Species trees from all methods contain two groups, one corresponding to species from the Sierra de los Cuchumatanes and the other containing all remaining species. In most cases, species formation within the genus involved an even division of the geographical range of the ancestral species between descendant species. The ancestor of extant Dendrotriton species was estimated to have occurred in either the Sierra de los Cuchumatanes or the Sierra Madre de Chiapas, and both of these areas appear to have been important for diversification within the genus. The single species found in the Quaternary‐age Guatemalan volcanic cordillera dispersed to the volcanoes from an older highland area.Main conclusions Models of geographical range evolution, when combined with robust species‐tree estimates, provide insight into the historical biogeography of taxa not available from phylogenies or distributional data alone. Vicariant species formation, rather than peripatric or gradient speciation, appears to have been the dominant process of diversification, with most divergence events occurring within or between ancient highland areas. The apparent dispersal of Dendrotriton to the Quaternary‐age volcanoes raises the possibility that the rich salamander community there is composed of species that dispersed from geologically older areas. The Motagua Valley appears not to have been as important in vicariant species formation within Dendrotriton as it is within other groups.

Investigation of an Argyre basin ring structure using Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars

The Argyre basin, a large impact basin in the southern highlands of Mars, excavates early Noachian geologic units and thus is an ideal probe of the compositional layering of ancient highland crust. A ring structure defined by circumferential graben is believed to represent the outermost topographic scarp of the basin. Two distinct layers in the fluvially dissected highland plains unit Npld have been exposed by the ring graben in northwest Argyre: a lower unit enriched in high‐calcium pyroxene and an upper unit showing laterally extensive occurrences of phyllosilicates, including chlorite and iron‐magnesium smectite. These phyllosilicates closely follow the unit contact between unit Npld and Hpl3 in this region; the Hesperian‐aged Hpl3 caprock directly covers unit Npld. Two nearby knobs also show phyllosilicate‐bearing materials over a high‐Ca pyroxene‐enriched unit, although the knobs are located in regions mapped as Npl1 and Nplh. From these observations, we suggest that an extensive layer of phyllosilicates underlying a layer of high‐Ca pyroxene‐bearing rock existed in the region prior to the Argyre impact. These materials were thrown up by the impact event and deposited as an inverted flap. This inverted flap of ejecta was then cut by the circumferential graben that formed as the transient Argyre crater collapsed, exposing the materials.

Diachronic Investigations of Mitochondrial and Y-Chromosomal Genetic Markers in Pre-Columbian Andean Highlanders from South Peru

This study examines the reciprocal effects of cultural evolution, and population dynamics in pre-Columbian southern Peru by the analysis of DNA from pre-Columbian populations that lived in the fringe area between the Andean highlands and the Pacific coast. The main objective is to reveal whether the transition from the Middle Horizon (MH: 650-1000 AD) to the Late Intermediate Period (LIP: 1000-1400 AD) was accompanied or influenced by population dynamic processes. Tooth samples from 90 individuals from several archaeological sites, dating to the MH and LIP, in the research area were collected to analyse mitochodrial, and Y-chromosomal genetic markers. Coding region polymorphisms were successfully analysed and replicated for 72 individuals, as were control region sequences for 65 individuals and Y-chromosomal single nucleotide polymorphisms (SNPs) for 19 individuals, and these were compared to a large set of ancient and modern indigenous South American populations. The diachronic comparison of the upper valley samples from both time periods reveals no genetic discontinuities accompanying the cultural dynamic processes. A high genetic affinity for other ancient and modern highland populations can be observed, suggesting genetic continuity in the Andean highlands at the latest from the MH. A significant matrilineal differentiation to ancient Peruvian coastal populations can be observed suggesting a differential population history.