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In recent decades, East Borneo has become an increasingly important archaeological "hot-spot" in Island Southeast Asia as a result of early dates for rock art ca. 38,000 BP and the greater number of excavated sites that support a much longer period of human occupation. However, the chronology of settlement and adaptation to environmental changes during the Pleistocene–Holocene transition is still poorly known. Here we report on an excavation at the Liang Abu rock shelter which has contexts dating from the Late Pleistocene (12,660 ± 58 uncal. BP) to the present day, indicating a terminus ante quem (TAQ) for human occupation at 23,790 BP. We present the results of an attempt to systematically integrate and compare data from Liang Abu and Kimanis, a geographically close site with a previously published sequence. Particular attention is paid to post-depositional issues in tropical settings and to data compatibility, reuse, and reproducibility, relying on open-source software for data processing (R scripts) and Bayesian chronological modeling. Two Bayesian models are built and compared using the ChronoModel software, which can handle outliers and uncertainty (e.g., freshwater reservoir effect). This first inter-site comparison for Borneo results in a new chronology of human settlement and mainland–coastal interactions in East Borneo and paves the way for future regional synthesis. [ABSTRACT FROM AUTHOR]

The Oaxacan Complex Carboniferous-Permian sedimentary cover in southern México records provenance shifts through time, reflecting the collision between Gondwana and Laurentia to amalgamate Pangea. The integration of petrological analysis and LA-ICP-MS U-Pb zircon geochronology from Santiago, Ixtaltepec and Yododeñe formations compared with adjacent terranes suggests that: (1) during the Early Mississippian, the Santiago Formation received sediments mainly from local sources such as the Oaxacan Complex and Tiñu Formation, with minor contributions from adjacent peri-Gondwana sources. The magmatic activity may have started during this time (~359–346 Ma) (2) during the Late Mississippian (Ixtaltepec Formation), detrital zircon grains of Ediacaran-Cambrian age are dominant, derived from sediments either related to the Pan-African/Brasiliano orogeny or the opening of the Iapetus Ocean; (3) during the Late Mississippian-Middle Pennsylvanian, intercalated marine volcaniclastic sandstone (Ixtaltepec Formation) provides the first record of Carboniferous arc-related volcanism reported in southern Mexico, dated between 330 and 308 Ma; (4) the early Permian Yododeñe Formation records the exhumation and erosion of the sedimentary cover during the final stage of Pangea assembly. Rhyodacitic subvolcanic sills and lavas dated at ~282–270 Ma are present throughout the succession. Volcanism and ca. 360–308 Ma detrital zircon grains could be associated with a Carboniferous magmatic arc formed by subduction of the Rheic oceanic plate beneath Gondwana. Slightly younger detrital zircon and subvolcanic rocks dated at ~300–270 Ma are linked to a western Pangea arc developed in response to the subduction of the Paleo-Pacific Ocean following Pangea assembly. Our results suggest that the Carboniferous-Permian units were deposited in a peri-arc basin, sharing sediment provenance with the Maya and Coahuila blocks, the Sierra de Juárez Complex, and northwestern South America. [ABSTRACT FROM AUTHOR]

The Pseudoreticulatispora confluens–P. pseudoreticulata spore-pollen zonal datum typically coincides with the end of widespread Permian glacial deposits in Western Australia. Although previously attributed to the mid-Sakmarian, chemical abrasion isotope dilution thermal ionisation mass spectrometry (TIMS) dating of zircons from volcanic tuffs in the Ditji Formation of the Bonaparte Basin and the Grant Group in the Canning Basin point to an Asselian age of about 295.25 Ma for this datum. All dated zircons from the Ditji Formation came from petroleum well cuttings but the accompanying palynology was mostly from sidewall cores; however, all Grant Group samples were from conventional core. TIMS dates from the Ditji Formation range in age from 295.2 to 292.7 Ma whereas the only productive tuff from the Grant Group yielded a 296.26 Ma date. By comparison, there are no zircon dates to constrain the onset of glacial deposition in Australia. The Bonaparte Basin ages overlap with those for the Edie Tuff (296.1–294.5 Ma) in Queensland's Galilee Basin, approximately 2000 km to the southeast, which also lies close to the base of the P. pseudoreticulata Zone. To date the only fossil group within the P. confluens Zone in Western Australia to provide independent age control, albeit loosely, are goniatites from the northern Perth Basin (Uraloceras irwinense and Juresanites jacksoni) that have consistently been attributed to the Sakmarian; these require a reassessment of their affinity with Russian faunas and therefore to global stratotypes. The position of the Carboniferous–Permian boundary is elusive in Australia and will remain so until additional volcanic tuffs containing young datable zircons are found; however, spore-pollen and zircon dates from Namibia place this boundary within the P. confluens Zone. [ABSTRACT FROM AUTHOR]

Granitoids, an important part of the continental crust, are the direct and indelible evidence of the accretion and reworking process of the continental crust in different tectonic settings. Therefore, these early geodynamic mechanisms can be roughly reconstructed by analysing the geochemical characteristics of granitoids. In this study, the Permian–Triassic Granitoids widely distributed in the East Kunlun Orogenic Belt (EKOB) are studied to determine their chronology and petrogenesis to restrict their source regions and establish the significance of their geodynamic and crustal growth. Zircon inductively coupled plasma mass spectrometry (ICP–MS) dating results show that the crystallization ages of these granitoids are between 252–240 Ma, during the early and middle Triassic. These granitoids have high SiO2 and medium Na2O + K2O contents, plotting into the granite region, and calc-alkaline to high-K calc-alkaline series on the SiO2–Na2O + K2O and SiO2–K2O diagrams, respectively. All the samples have aluminium saturation index (A/CNK) values from 1.00 to 1.25 showing peraluminous characteristics. In terms of trace and rare earth elements, the samples are depleted in high field strength elements (HFSEs) such as Nb, Ta, P, and Ti and are enriched in large ion lithophile elements (LILEs) such as Rb, K, Ba, and U. Moreover, all granitoids show right-inclined rare earth element (REE) distribution patterns with weak to moderate Eu anomalies (δEu = 0.50–0.93). In addition, the samples have low P2O5 contents, 10,000*Ga/Al ratios (1.65–2.39), and Zr + Nb + Ce + Y (212–262 ppm) displaying affinities to I-type granite. Combined with their εHf (t) values of −2.31 to 4.44, with 1.0–1.4 Ga two stage model ages (TDM2), they are considered to be the products of the reworking of the Mesoproterozoic lower crust; therefore, they are not related to the continental net growth in the EKOB. On the tectonic discrimination diagrams of granitoids, all the samples fall into the area of volcanic arc granite (VAG) and continental margin arc; this suggests that the Paleo-Tethys Ocean slab was still in the subduction stage during 252–240 Ma, and the continental collision had not yet started. Based on the plenty of magmatic rock dating results published previously, it appears there are two magmatic peak periods (260–240 Ma and 230–210 Ma) and one magmatic intermittence period (240–230 Ma) during the late Permian to Triassic of the EKOB, corresponding to three geodynamic evolution stages of subduction, post-collision extension, and syn-collision, respectively. [ABSTRACT FROM AUTHOR]

In central Victoria, inherited zircon in Devonian igneous rocks and detrital zircon in metasedimentary country rocks and an amphibolite-facies xenolith show that Mesoproterozoic parts of the underlying Selwyn Block cannot be the source for all the silicic magmas. Zircon inheritance in S-type samples reveals significant thermal events at 525–425 Ma and 1200–1100 Ma. Both S- and I-type samples have prominent zircon age peaks at 420–410 Ma, which record high-grade metamorphism of the deep crust during the terminal phases of the Benambran and Bindian orogenies. All I-type rocks have 650–500 Ma peaks, suggesting derivation from an arc-related metavolcanic source in the upper Selwyn Block. Protoliths of the greenschist-facies Ordovician metasediments and the amphibolite-facies Cambrian metasedimentary xenolith were deposited in distal backarc settings. Most inherited zircon cores are metamorphic, and the strongest zircon inheritance occurs in hornblende-bearing I-type rocks, highlighting their largely crustal origin. Zircon populations at ca 1400 Ma, thought to signal sediment derivation from East Antarctica and Rodinia-Nuna, are mostly absent in I-type samples and some S-types. The ca 1400 Ma signal probably applies to the upper, metasedimentary Selwyn Block, so Devonian S-type magmas were sourced mainly in the deeper sections. Zircon inheritance in the Devonian igneous rocks was not influenced by the exposed metasedimentary country rocks. Two samples from one of the smaller plutons have contrasting patterns of zircon inheritance, suggesting relatively small-scale source heterogeneity. Many rounded and corroded cores in zircon crystals yield the same ages as the crystallisation dates for the rocks, and thus are antecrysts. Higher whole-rock Zr contents generally correlate with higher proportions of inherited zircon, and differentiation does not affect this relationship. The degree of partial melting of a magma source and the efficiency of crystal entrainment are critical in governing zircon inheritance. Mesoproterozoic sections of the Selwyn Block cannot be the sources for all the Devonian silicic magmas in central Victoria. I-type rocks have 650–500 Ma zircon age peaks, suggesting derivation from arc-related metavolcanic rocks in the upper Selwyn Block. Hornblende-bearing I-type rocks have the strongest zircon inheritance patterns, indicating the largely crustal origins of I-type magmas. Exposed metasedimentary country rocks were not involved in magma genesis. [ABSTRACT FROM AUTHOR]

Metamorphic rocks from the Diancang Shan (DCS) complex along the Ailao Shan-Red River belt between the South China plate and Simao-Indochina block are studied in this contribution to constrain the Proto- to Palaeo-Tethys tectonic evolution of the eastern Tethys domain. LA-ICP-MS zircon U-Pb geochronological dating is conducted in this study on the metasedimentary rocks (garnet-biotite-plagioclase gneisses, biotite-quartz schists and phyllonites) from different stratigraphical horizons (Proterozoic and Triassic) of the DCS complex. The analyses yielded three major age peaks at ca. 248 Ma, ca. 441 Ma, ca. 1000–900 Ma and one subordinate age peak at ca. 828 Ma. The youngest ages for the samples help to constrain the maximum ages of deposition of the complex at Early Carboniferous and Late Triassic, respectively. The existence of the diagnostic age peak at ca. 440 Ma and the euhedral-subhedral morphology of the detrital zircons in the Palaeozoic and Mesozoic strata may indicate that there were early Palaeozoic magmatic activities along the eastern margin of the Simao-Indochina block. At the meantime, the age peak at ca. 440 Ma was never reported in the early Palaeozoic strata from the western margin of the South China plate, which supports the existence of an early Palaeozoic rift zone, i.e., the Proto-Tethys Jinsha Jiang-Ailao Shan-Song Ma rift zone, being consistent with geochemical discriminations. Furthermore, we conclude, from the significant difference between detrital zircon age data of Silurian to Devonian sedimentary rocks from the Simao-Indochina block and South China plate, the opening of the Palaeo-Tethys ocean since Early Carboniferous, the absence of evidence for the Palaeozoic orogeny, and the successive sedimentation from the Cambrian to Triassic along the western margin of the South China plate, that the Proto-Tethys rifting and subsequent Palaeo-Tethys ocean evolution along the Jinsha Jiang-Ailao Shan-Song Ma zone formed actually a complete 'Wilson Cycle' from early Palaeozoic to the Late Triassic. [ABSTRACT FROM AUTHOR]

With new direct dates from rock paintings comes an unprecedented opportunity to relate excavated archaeological data to the parietal record in southern Africa's Maloti-Drakensberg Mountains. Anchoring dated art to recovered palaeoenvironmental, faunal and technological data enables the incorporation into socioecological models of ideational inferences, affording insights into how hunter-gatherers perceived their mountain habitats. Of particular interest is the late Holocene Neoglacial (∼3.5–2 kcal BP), during which skilled paintings were being made just as the region experienced dynamic changes owing in part to climate change. Responses of local foragers are evident across a range of cultural spheres, including dramatic subsistence transformations. With the Maloti-Drakensberg's well-known "traditional corpus" of fine-line art now known to extend back to at least 3 kcal BP, here we explore how such changes may have precipitated – and in turn been influenced by – ontological shifts in relation to the food quest. As desirable game declined and hunting windows narrowed, we suggest that Neoglacial foragers sought to manage scheduling and social conflicts through enhanced spiritual negotiation with non-human entities in the landscape. Facilitated by the supernaturally charged nature of their elevated cosmos, this intensified spiritual labour may have found material expression in an elaborate new style of painting. [ABSTRACT FROM AUTHOR]

Peesey Swamp on southern Yorke Peninsula, southern Australia, is a north-northwesterly—south-southeasterly trending lowland depression, approximately 24 km long and 4 to 10 km wide. The richly fossiliferous mollusc and foraminiferal faunal assemblages of the last interglacial Glanville Formation in Peesey Swamp indicate that the paleoenvironment was a low- to medium-energy, sheltered sandflat to shallow-water seaway during the Last Interglacial Maximum (Marine Isotope Substage [MIS] 5e; 128–116 ka). The presence of the fossil bivalve molluscs Katelysia rhytiphora, Chlamys (Equichlamys) bifrons and Fulvia tenuicostata, in life position, indicate that the paleowater depth was ≤4 m in Peesey Swamp. The seaway cut across southern Yorke Peninsula, establishing a marine connection between southern Spencer Gulf and Investigator Strait during deposition of these taxa. Amino acid racemisation dating of the fossil marine molluscs Katelysia sp. and Fulvia tenuicostata confirms that the shelly assemblages at Peesey Swamp are correlative with the last interglacial Glanville Formation, a succession of richly fossiliferous, mixed quartz–skeletal carbonate sands documented from many sites along the southern Australian coastline. This study illustrates the significant changes in the geographical configuration of coastlines that may accompany relatively modest (<5 m) sea-level changes on low-gradient coastal landscapes. Peesey Swamp on southern Yorke Peninsula was flooded by seawater forming a 4 to 10 km-wide seaway during the Last Interglacial Maximum (MIS 5e). Fossil mollusc and foraminiferal assemblages reveal deposition within shallow subtidal to intertidal sandflat environments indicating that the paleowater depth and height of sea-level in Peesey Swamp was ≤4 m. Amino acid racemisation dating of fossil marine molluscs confirms that the shelly assemblages at Peesey Swamp are of last interglacial (MIS 5e) age. The distribution of the foraminifer Marginopora vertebralis indicates that the eastward flow of the warm-water Leeuwin Current, during the Last Interglacial Maximum, was retarded by the biogeographical barriers of Kangaroo Island and Fleurieu Peninsula. [ABSTRACT FROM AUTHOR]

Lineage through time plots (LTTs) are often used to explore past patterns of lineage diversification and community assembly. However, as they are based solely on extant species their ability to accurately depict past events can be questioned. Here, simulation models based on neutral processes are used to explore immigration and extinction scenarios to assist with interpretation of LTT plots generated from molecular clock age estimates for a nearly complete set of extant New Zealand vascular plant genera. With significant genus turnover, model simulations yield smooth exponential and linear semi-log LTT plots. Abrupt changes in extinction and immigration rates imposed in the scenarios caused only slight alterations of the curves. The vast majority of New Zealand vascular plant genera derive from trans-oceanic dispersal, and LTT plots generated from divergence dates and fossil data indicate consistently high turnover. Even major geological and climatic events leave minor signatures on LTT plots. Most notably, the maximum Oligocene Marine Transgression (27–22 Ma), when at least 85% of the current landmass was inundated, isn't clearly registered. By themselves, LTT plots shed little light on the biotic effects of climatic or geomorphic change in the remote past and need to be interpreted in the light of fossil and geological data. [ABSTRACT FROM AUTHOR]

Modern and fossil populations of a Stephanodiscus Ehrenberg species from June Lake, California (USA) were analysed using light and scanning electron microscopy (SEM). Stephanodiscus valves were a major constituent of almost all analysed samples, often dominating fossil assemblages dating back several thousand years. The most commonly observed Stephanodiscus specimen in the samples bore a striking resemblance to the extinct Late Pliocene species Stephanodiscus klamathensis, particularly under light microscopy. The population size range, ultrastructure, and other defining characteristics closely matched published information on S. klamathensis. However, under SEM, internal views of the specimens from June Lake showed an important difference; specimens lacked valve face fultoportulae, whereas S. klamathensis is characterized by the presence of two valve face fultoportulae, each with three satellite pores near the centre of the valve. Additional differences in valve size range, absence of fultoportulae on the valve face, and the fact that S. klamathensis is an extinct species (observed in diatomites deposited from Late Pliocene to Pleistocene) with no closely related living relatives, necessitates describing this Stephanodiscus as a new species. To date, Stephanodiscus coruscus has been observed only in June Lake, California; most Stephanodiscus that share strong morphological similarities to this species have only been observed in ancient fossil diatomites. Thus, Stephanodiscus coruscus Jeff. R. Stone, Edlund & Streib sp. nov. is not only a new species but also provides a rare glimpse into the likely types of environments that S. klamathensis and other similar ancient Stephanodiscus may have inhabited in the late Pliocene. Character variations between S. coruscus and S. klamathensis reveal potential patterns of evolution in freshwater lineages, such as character loss, over time. [ABSTRACT FROM AUTHOR]

We address the growing controversy about the tectonic setting in which Jurassic magmatism of Iran occurred: arc or continental rift. In the Ghorveh area of the northern Sanandaj Sirjan zone (SaSZ), the Ghalayan metabasites are interlayered with marble and schist and locally cut by acidic dikes. Zircon U-Pb dating of the metabasitic rocks shows that these crystallized at ca. 145–144 Ma ago in the Late Jurassic (Tithonian). This complex was metamorphosed in the lower greenschist facies, however, some protolithic structures such as pillow lava and primary minerals are preserved. The metabasites are tholeiites with low SiO2 (45.6–50.5 wt.%), moderate Al2O3 (11.3–17.0 wt.%), and high TiO2 (0.7–2.9 wt.%) and Fe2O3 (9.4–14.1 wt.%). The Ghalayan metabasites are enriched in Light rare earth elements (LREEs) without significant Nb, Ta, Pb, Sr and Ba anomalies, similar to modern continental intra-plate tholeiitic basalts such as Afar and East African rifts. The Ghalaylan metabasites show wide ranges for 87Sr/86Sr(i) (0.7039–0.7077) and positive εNd(t) values (+0.1 to +4.6). These isotopic compositions are similar to those expected for slightly depleted subcontinental lithospheric mantle sources. Independently built discrimination diagrams indicate an intra-continental rifting regime for the source of Jurassic metabasites in the northern SaSZ. Geochemical and tectonic evidence suggests that rifting or a mantle plume was responsible for volcanic activity in the Upper Jurassic SaSZ. Considering the variation of ages of basaltic volcanism along the SaSZ, we suggest that Ghalayan basaltic magmatism reflected a submarine volcano that formed as part of the late stage continental rift, similar to Afar in the East African Rift system. Our results indicate that an extensional tectonic regime dominated SaSZ tectonics in the Middle to Late Jurassic. [ABSTRACT FROM AUTHOR]

It is well known that flowers use scents to attract pollinators and that these fragrances are composed of a mixture of different chemical compounds, many of which form the basis of perfumes and colognes we use today. An examination of fossil flowers in mid-Cretaceous Burmese amber and mid-Tertiary Dominican amber revealed a range of secretory tissues in the form of nectaries, glandular trichomes, eliaphores and osmophores. These tissues most certainly secreted liquids and volatiles to attract pollinators, just as they do in modern flowers. The morphological similarities of secretory tissues found on fossil flowers dating back to 100 mya to those of their present day descendants suggests that ancient and modern flowers may have produced similar essences, including those used in the production of today's perfumes and colognes. [ABSTRACT FROM AUTHOR]

Two well-preserved delphinid crania have been recovered from the Haraichi Formation, Annaka Group, Gunma Prefecture, Japan (earliest late Miocene, Tortonian; 11.29–11.25 Ma). The specimens represent a new genus and species of delphinid, Norisdelphis annakaensis. The new species is characterized by transversely narrow and anteroposteriorly elongated external bony nares, and a wider proximal extremity of the left premaxilla. Phylogenetic analysis suggests that Norisdelphis is the most basal member of the Delphinidae. The previous oldest known described delphinid, Eodelphinus kabatensis, is from the upper Miocene (ca. 9 Ma), and other reliably dated and described fossil delphinids are no older than Pliocene; thus, N. annakaensis is the oldest convincingly dated and well-diagnosed fossil delphinid species yet described. Norisdelphis annakaensis expands the geological range of the family Delphinidae. [ABSTRACT FROM AUTHOR]

This article presents new zircon U-Pb geochronology, Hf isotopic, and whole-rock major- and trace-element geochemical data that provide insights into the petrogenesis and tectonic history of the Riwanchaka granodiorite porphyries of Central Qiangtang, Tibet. Zircon U-Pb ages of 236-230 Ma indicate an early Late Triassic age of emplacement of the porphyries, and zircon Hf isotopic data yield εHf(t) values of - 7.0 to - 1.5 and ancient zircon Hf crustal model ages (TDMC) of 1524-1220 Ma. The granodiorite porphyries are characterized by low K2O contents, high Mg# values, and relatively high Cr and Ni contents. They are classified as I-type calc-alkaline granite and are considered to have formed through the anatexis of ancient mafic crustal rocks with contributions from mantle-derived components. The geochemistry and isotopic compositions of all samples are similar to those of magmatic rocks that originated in the South Qiangtang crust. However, field observations indicate that the pluton intrudes the North Qiangtang crust, and we propose that the granodiorite porphyries were derived by partial melting of subducted continental crust of the South Qiangtang terrane. These new data have been integrated with data from previous studies to construct a new model of slab rollback during northward subduction of the Southern Qiangtang continental crust at ca. 245-226 Ma, thereby improving our understanding of magmatic processes involved in continental subduction in collision settings. [ABSTRACT FROM AUTHOR]

The Pliocene-Quaternary volcanics in NE Turkey are mainly hornblende-phyric trachyandesites having a narrow range of SiO2 from 61.88 to 63.00 wt.% and exhibiting adakitic signatures with their Na2O (3.67-4.27 wt.%), Al2O3 (16.19-16.80 wt.%), Y (14.1-16.5 ppm) contents and K2O/Na2O (0.87-1.12), Sr/Y (44.24-54.90), and La/Yb (36.80-43.88) ratios. Plagioclases as the main mineral phases show a wide range of compositions, and weak normal and reverse zoning. Hornblendes are generally edenite and pargasite (Mg#: 0.39-0.74). Clinopyroxenes are augite (Mg#: 0.58-0.76). Biotites have Mg# ranging from 0.45 to 0.66. The textural and compositional variations indicate disequilibrium crystallization possibly arising from magma mixing. The U-Pb zircon dating of the adakitic volcanics yielded 3.4-1.9 Ma. The studied rocks display moderate light rare earth element /heavy rare earth element ratios and enrichment in the lithophile element and depletion in high field strength element, implying that the parental magmas were derived from mantle sources previously enriched by slab-derived fluids and/or subducted sediments. The crystallization temperature and pressure estimations based on the clinopyroxene thermobarometry range from 1144 to 1186°C and from 3.92 to 7.97 kbar, respectively. Hornblende thermobarometry, oxygen fugacity, and hygrometer calculations yielded results as 908-993°C at a pressure of 2.87-5.22 kbar, water content of 4.4-8.4 wt.%, and relative oxygen fugacity (ΔNNO log units) of −0.6 to 0.9, respectively. Biotite thermobarometry suggests relatively higher oxygen fugacity conditions (10-13.33 to 10-17.60) at temperatures of 676-819°C and at pressures from 1.15 to 1.76 kbar. In the light of the obtained data and modelling, it can be concluded that the magmas of the adakitic volcanics were derived from enriched mantle source through relatively higher partial melting and experienced magma mixing with melts at the crustal level. Additionally, the fractional crystallization and assimilation-fractional crystallization processes may have played an important role during the evolution of the studied volcanics. [ABSTRACT FROM AUTHOR]

Sıcak Çermik (Sivas) is an important geothermal and recent travertine formation area in Central Anatolia. The majority of travertines found in the region comprise fissure-ridge type travertines according to morphological classification. At the location called Tepe Çermik within the travertine area, fill containing fossil bone fragments of Equus sp., Bovidae and other abundant animals formed within the fracture axis of a N-S striking fissure-ridge travertine developed under control of tectonic forces. The finds of these fossils in fissure-ridge travertines linked to tectonic forces indicates formation of a unique fossil environment created under the control of these forces. The Accelerator Mass Spectrometry Radiocarbon Dating analyses of fossils from the study area determined the fills were older than 43,000 years. The U/Th age of a sample from the most recently-formed banded travertine in the axis of the fracture was identified as 278,540 ± 18,436 years. As a result, the ages of fossils found within this fill are thought to be between 43,000 and 278,540 ± 18,436 years old. The high amount of perissodactyla and artiodactyla fossils found within fill in the axis of the fissure-ridge travertine probably indicates the presence of hominids who chose the region for hunting or settlement. The Equus sp. and Bovidae fossil samples found in the axis of the fracture indicate that in the dry and cold glacial period the paleogeography in a large portion of Anatolia comprised desert-like steppe. [ABSTRACT FROM AUTHOR]

Precise time constraints of the main extrusive phase of the Emeishan large igneous province (ELIP) remain unresolved because basalts commonly do not contain suitable minerals for U-Pb dating, whereas previous 40Ar/39Ar studies on basalts yielded tectonothermal overprint ages. The timing for the ELIP was deduced from indirect dating of minor intrusions of ultramafic/mafic and felsic compositions by geochronological methods and geological correlations. The extrusive part of the ELIP consists of an older low-Ti and younger high-Ti basalt phases. We have found fresh samples of plagioclase-phyric rocks at the lower Qiaojia extrusive section (the Yunnan province of China), which belong to the ELIP unit of the high-Ti basalt series. 40Ar/39Ar dating on plagioclase from two samples conducted at two different laboratories using different age standards yielded statistically indistinguishable results with the weighted mean age of 260.1 ± 1.2 Ma for five individual measurements. This provides the direct constraints on the onset of the ELIP high-Ti basalt extrusive phase. The obtained age is within the error or slightly older than the age of the Guadalupian-Lopingian boundary and felsic ignimbrite capping the ELIP lava succession (both dated at 259.1 ± 0.5 Ma). Our new data are strengthening the short duration of the, at least, high-Ti phase of the ELIP volcanism and its temporal link with the end-Guadalupian mass extinction. Estimation of the total duration of the ELIP volcanism awaits finding of suitable for dating low-Ti basalts. [ABSTRACT FROM AUTHOR]

The southern Midyan terrane is a composite Tonian to Ediacaran tectonostratigraphic crustal block in the northern Arabian Shield that prior to Red Sea opening was contiguous with coeval rocks in the Eastern Desert of Egypt and Sinai. Ion microprobe (sensitive high-resolution ion microprobe [SHRIMP]) dating of 12 rock samples described here and the results of other dating programmes establish a clear timeframe for depositional, intrusive, and structural events in the region and provide a chronology of tectonism in this part of the Arabian-Nubian Shield. Deposition of Zaam and Bayda group volcanosedimentary rocks and emplacement of mafic-ultramafic complexes and TTG-type diorite, tonalite, and granodiorite denote formation of the Tonian (780-715 Ma) Zaam arc and fore-arc ophiolite above a possible west-dipping subduction system in the southern part of the Midyan terrane. Convergence with the Hijaz terrane farther south and obduction of ophiolite nappes resulted by ~700 Ma in development of the Yanbu suture. Ongoing or a new subduction system led to a ~705-660 Ma Cryogenian pulse of magmatism represented by I-type calc-alkaline diorite, granodiorite, and granite that have volcanic-arc and syn-collisional granite affinities. This was followed, after a brief end-Cryogenian hiatus, by a 635-~570 Ma period of Ediacaran magmatism marked by monzogranite, syenogranite, and minor gabbro and diorite. These rocks are reported to have within-plate to volcanic-arc and syncollision chemical characteristics but their precise tectonic setting is uncertain. Structurally, the intrusions are diapiric and were evidently emplaced in an extensional regime consistent with an overlap between intrusion and Najd faulting associated, at this time, with transpressional collision and northward extension through much of the ANS. Terminal magmatism in the southern Midyan terrane postdated cessation of Najd faulting at ~575 Ma and resulted in the emplacement of undeformed within-plate A-type alkali-feldspar granites and mafic (lamprophyre) and felsic dikes. [ABSTRACT FROM AUTHOR]

The Jurassic magmatic and volcanic rocks are widespread along the west central Lhasa subterrane. However, the petrogenesis of these rocks is poorly understood because of lacking high-quality geochronology and geochemical data. Here, we present new zircon U-Pb age and Hf isotopic data, whole-rock geochemical and Sr-Nd-Pb isotopic data for the Songduole and Qiangnong plutons in Geji area. LA-ICP-MS dating of zircon yield crystallization ages of 172.1 ± 1.9 and 155.9 ± 1.2 Ma for the Songduole and Qiangnong plutons, respectively. Geochemically, Songduole and Qiangnong granodiorite are characterized by high MgO (2.63-3.49 wt%), high Mg# (49-50), and low TiO2 (0.48-0.57 wt%). Besides, all rocks show metaluminous, calc-alkaline signatures, with strong depletion of Nb, Ta, and Ti, enrichment of large-ion lithophile (e.g. Rb, Th, K), and a negative correlation between SiO2 and P2O5. All these features are indicative of arc-related I-type magmatism. Five samples from the Songduole granodiorite have whole rock (87Sr/86Sr)i of 0.71207-0.71257, εNd(t) values of −15.1 to −13.9, zircon εHf(t) values of −17.4 to −10.5, (206Pb/204Pb)t ratios of 18.402-18.854, (207Pb/204Pb)t ratios of 15.660-15.736, and (208Pb/204Pb)t ratios of 38.436-39.208. Samples from the Qiangnong granodiorite have (87Sr/86Sr)i of 0.71230-0.71252, εNd(t) values of −15.1 to −14.2, zircon εHf(t) values of −12.6 to −6.4, (206Pb/204Pb)t ratios of 18.688-18.766, (207Pb/204Pb)t ratios of 15.696-15.717, and (208Pb/204Pb)t ratios of 38.546-39.083. These geochemical signatures indicate that the two plutons most likely originated from partial melting of the ancient Lhasa lower crust with obvious inputs of mantle-derived melts. Combined with regional geology, our results indicate that the Jurassic magmatism in the west central Lhasa subterrane most likely resulted from the southward subduction of the Bangong Ocean lithosphere beneath the central Lhasa terrane. [ABSTRACT FROM AUTHOR]

The late Carboniferous to Triassic tectonic history of eastern Australia includes important periods of regional-scale crustal extension and contraction. Evidence for these periods of tectonism is recorded by the extensive Pennsylvanian (late Carboniferous) to Triassic basin system of eastern Australia. In this study, we investigate the use of U-Pb dating of detrital zircons in reconstructing the tectonic development of one of these basins, the eastern Galilee Basin of Queensland. U-Pb detrital zircon ages were obtained from samples of stratigraphically well-constrained Cisuralian and Lopingian (early and late Permian, respectively) sandstone in the Galilee Basin. Detrital zircons in these sandstones are dominated by a population with ages in the range of 300-250 Ma, and ages from the youngest detrital zircons closely approximate depositional ages. We attribute these two fundamental findings to (1) appreciable derivation of detrital zircons in the Galilee Basin from the New England Orogen of easternmost Australia and (2) syndepositional magmatism. Furthermore, Cisuralian sandstone of the Galilee Basin contains significantly more >300 Ma detrital zircons than Lopingian sandstone. The transition in detrital zircon population, which is bracketed between 296 and 252 Ma based on previous high-precision U-Pb zircon ages from Permian ash beds in the Galilee Basin, corresponds with the Hunter-Bowen Orogeny and reflects a change in the Galilee Basin from an earlier extensional setting to a later foreland basin environment. During the Lopingian foreland basin phase, the individual depocentres of the Galilee and Bowen basins were linked to form a single and enormous foreland basin that covered >300 000 km2 in central and eastern Queensland. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Gawler Silicic Large Igneous Province (SLIP) in the Gawler Craton and Curnamona Province, southern Australia, comprises extensive felsic and lesser mafic volcanic sequences, with only limited sedimentary successions. The Roopena Basin is a rare example of a synvolcanic sedimentary basin that formed within the Gawler SLIP in the eastern Gawler Craton. It is a north-south-trending basin with a preserved area of 75 km2, bound by the Roopena and Wizzo Well faults, and contains three units of the lower Gawler Range Volcanics; the Angle Dam Dacite, Fresh Well Formation and Roopena Basalt. The Angle Dam Dacite is a porphyritic lava and the oldest part of the volcanic succession, directly overlying basement. The Fresh Well Formation overlies the Angle Dam Dacite or basement, comprises three coarsening-upwards volcaniclastic packages of claystone, siltstone, fine-grained to coarse-grained lithic sandstone and conglomerate deposited in a fluvio-lacustrine setting, and contains three tuff members. The Roopena Basalt is interlayered with the Fresh Well Formation, and comprises auto-brecciated lavas that exhibit only local interaction with water or wet sediment. Sharp basal contacts of the prograding packages within the Fresh Well Formation provide evidence of rapid flooding events within the basin. New detrital zircon geochronology of a sandstone within the Fresh Well Formation yielded a maximum depositional age of ca 1580 Ma, with provenance dominated by felsic volcanic units of the 1635-1605 Ma St Peter Suite. Sedimentation in the Gawler SLIP appears to have occurred in isolated basins with limited areal extent. It was largely restricted to the eastern Gawler Craton, and as well as the Roopena Basin, and includes similar basins at the Olympic Dam and Prominent Hill iron oxide-copper-gold ± uranium (IOCG ± U) deposits. The coincidence of sedimentation and mafic volcanism in the eastern Gawler Craton suggests that this region underwent extension at this time, although high-temperature metamorphism and compressional deformation occurred in some parts of the Gawler Craton and Curnamona Province synchronous with the Gawler SLIP. The Roopena Basin sedimentary rocks and underlying basement contain hematite-chlorite-sericite-white mica assemblages, permissive of hematite-style IOCG mineral deposits; however, no significant ore deposit has yet been discovered in the Roopena Basin. [ABSTRACT FROM AUTHOR]

We present our new investigation into the depositional environment and provenance of the Yingshuiquan Formation in the central Qiangtang region of northern Tibet, in order to further our understanding of the environment of the Longmu Co-Shuanghu Palaeo-Tethys during the Early Triassic. The Yingshuiquan Formation is composed of oolitic limestone, calcareous sandstone, calcarenite, thin-bedded ribbon limestone, bioclastic limestone, and coarse oolite limestone that were deposited in a shallow-marine basin and contain abundant Lower Triassic conodont fossils (e.g. Hadrodontina anceps, Pachycladina sp., gen. et sp, Pachyclaina oblique, Hibbardelloides sp). We selected detrital zircons from four calcareous sandstone samples for U-Pb dating, yielding minimum age peaks of 263, 269, 275, and 280 Ma, respectively, and a minimum age of 249 Ma, based on several zircons around the same age. Analysis of the conodont biofacies and zircon LA-ICP-MS dating of calcareous sandstone indicates that the data is consistent with deposition in the Early Triassic. The Yingshuiquan Formation records Early Triassic shallow-water sediment in the Longmu Co-Shuanghu Palaeo-Tethys, and has a Southern Qiangtang and Northern Qiangtang terranes provenance. During the Early Triassic, the carbonate sediments of the Yingshuiquan Formation were deposited in an active environment around the Longmu Co-Shuanghu Palaeo-Tethys, which has became a residual sea basin. [ABSTRACT FROM AUTHOR]

Liaoning Province in China is an area known for the occurrence of numerous copper and/or molybdenum deposits of variable size. However, the age of mineralization and tectonic setting in this region are still a subject of debate. In this study we describe the geology of these deposits and apply zircon U–Pb and molybdenite Re–Os isotopic dating to constrain their ages and define the metallogenic epochs of this province. The Huatong Cu–Mo deposit yields molybdenite Re–Os model ages of 127.6–126.3 Ma and an isochron age of 127.4 ± 0.7 Ma. The Dongbeigou Mo deposit yields molybdenite Re–Os model ages of 132.6–127.1 Ma, an isochron age of 128.1 ± 5.1 Ma, and a zircon U–Pb age of 129.4 ± 0.3 Ma for the associated monzogranite. The granodiorite associated with the Wanbaoyuan Cu–Mo deposit yields a zircon U–Pb age of 128.4 ± 1.1 Ma; the plagiogranite associated with the Yaojiagou Mo deposit yields an age of 167.5 ± 0.9 Ma; and the biotite–plagioclase gneiss from the Shujigou Cu deposit yields an age of 2549.4 ± 5.6 Ma. These results, together with previous geochronology data, show that intense Cu–Mo porphyry and skarn mineralization were coeval with Early–Middle Jurassic and Early Cretaceous granitic magmatism. The former was associated with the orogeny that followed the collision of the Siberian and North China plates and the resulting closure of the palaeo-Asian Ocean, and the latter with rifting that followed the subduction of the palaeo-Pacific Plate and associated lithospheric thinning. Volcanogenic massive sulfide Cu deposit. mineralization took place much earlier, in the late Archaean, and was related to continent–continent collision, palaeo-ocean closure, the formation of a united continental landmass, bimodal volcanism, magma emplacement, and subsequent metamorphism and deformation of syn-collisional granites. [ABSTRACT FROM PUBLISHER]

We determined detailed U–Pb ages for zircons in migmatitic granites densely exposed in the Namche Barwa peak (NBP) area, the core area of the eastern Himalayan syntaxis (EHS). The cores of these zircons show ages ranging from 863 to 1,256 Ma, with high Th/U ratios. These ages correspond to the crystallization age of the Proterozoic Indian continental basement. The majority of zircon rims from these migmatitic granites yield a significant age peak at about 8 Ma with an increase in Th/U ratios, suggesting that a large-scale partial crustal melting event occurred at 8 Ma in the NBP area. Because thermochronologic results have demonstrated that a rapid denudation started around 8 Ma, we interpret this large-scale partial melting of the crust as a decompression melting caused by rapid denudation in the NBP area. The rapid denudation at 8 Ma probably resulted from the combination of tectonic activities and surface erosion. [ABSTRACT FROM PUBLISHER]

In northwestern California, the Franciscan subduction complex has been subdivided into seven major tectonostratigraphic units. We report U-Pb ages of ≈2400 detrital zircon grains from 26 sandstone samples from 5 of these units. Here, we tabulate each unit’s interpreted predominant sediment source areas and depositional age range, ordered from the oldest to the youngest unit. (1) Yolla Bolly terrane: nearby Sierra Nevada batholith (SNB); ca. 118 to 98 Ma. Rare fossils had indicated that this unit was mostly 151–137 Ma, but it is mostly much younger. (2) Central Belt: SNB; ca. 103 to 53 Ma (but poorly constrained), again mostly younger than previously thought. (3) Yager terrane: distant Idaho batholith (IB); ca. 52 to 50 Ma. Much of the Yager’s detritus was shed during major core complex extension and erosion in Idaho that started 53 Ma. An Eocene Princeton River–Princeton submarine canyon system transported this detritus to the Great Valley forearc basin and thence to the Franciscan trench. (4) Coastal terrane: mostly IB, ±SNB, ±nearby Cascade arc, ±Nevada Cenozoic ignimbrite belt; 52 to <32 Ma. (5) King Range terrane: dominated by IB and SNB zircons; parts 16–14 Ma based on microfossils. Overall, some Franciscan units are younger than previously thought, making them more compatible with models for the growth of subduction complexes by progressive accretion. From ca. 118 to 70 Ma, Franciscan sediments were sourced mainly from the nearby Sierra Nevada region and were isolated from southwestern US and Mexican sources. From 53 to 49 Ma, the Franciscan was sourced from both Idaho and the Sierra Nevada. By 37–32 Ma, input from Idaho had ceased. The influx from Idaho probably reflects major tectonism in Idaho, Oregon, and Washington, plus development of a through-going Princeton River to California, rather than radical changes in the subduction system at the Franciscan trench itself. [ABSTRACT FROM AUTHOR]

The Güira de Jauco metamorphic sole, below the Moa-Baracoa ophiolite (eastern Cuba), contains strongly deformed amphibolites formed at peak metamorphic conditions of 650–660°C, approximately 8.6 kbar (~30 km depth). The geochemistry, based on immobile elements of the amphibolites, suggests oceanic lithosphere protholiths with a variable subduction component in a supra-subduction zone environment. The geochemical similarity and tectonic relations among the amphibolites and the basic rocks from the overlying ophiolite suggest a similar origin and protholith. New hornblende40Ar/39Ar cooling ages of 77–81 Ma obtained for the amphibolites agree with this hypothesis, and indicate formation and cooling/exhumation of the sole in Late Cretaceous times. The cooling ages, geochemical evidence for a back-arc setting of formation of the mafic protoliths, and regional geology of the region allow proposal of the inception of a new SW-dipping subduction zone in the back-arc region of the northern Caribbean arc during the Late Cretaceous (ca. 90–85 Ma). Subduction inception was almost synchronous with the main plume pulse of the Caribbean–Colombian Oceanic Plateau (92–88 Ma) and occurred around 15 million years before arc-continent collision (75 Ma–Eocene) at the northern leading edge of the Caribbean plate. This chronological framework suggests a plate reorganization process in the region triggered by the Caribbean–Colombian mantle plume. [ABSTRACT FROM AUTHOR]

High-precision Schmidt-hammer exposure-age dating ( SHD) is applied to ice-cored moraine-ridge complexes at three high-alpine glaciers in Jotunheimen and Breheimen, southern Norway. Local calibration curves were established using moraine ridges dating from the last 50 years and bedrock surfaces deglaciated ∼9700 years ago. SHD ages, with 95% statistical confidence intervals, ranged from 3920 ± 790 years to a negative (futuristic) age of -890 ± 580 years at Gråsubreen, 420 ± 700 to 260 ± 710 years at Vesle-Juvbreen and 2250 ± 450 to 1605 ± 410 years at Østre Tundradalskyrkjabreen. Negatively skewed R-value distributions were interpreted as the result of weathered boulders from reworked surfaces. This leads to the interpretation of these SHD ages as maximum estimates of moraine-ridge age. Østrem's hypothesis (that the proximal ridges are the oldest and survived being overridden many times) is rejected on the basis of our SHD ages. Although ice-cored moraine ridges resemble the flow structures of rock glaciers, Barsch's hypothesis (that these ice-cored moraine complexes are rock glaciers) is also rejected. Instead, the ice-cored moraine-ridge complexes are considered to be glaciotectonic structures produced by the interaction of polythermal glaciers and alpine permafrost over the late Holocene. All the individual ridges were essentially formed during the ' Little Ice Age' glacier advance from material deposited earlier by multiple neoglacial events. The considerable size of the moraine complexes is attributed not only to the accumulation of material from these different events over a long period of time but also to their survival in the landscape during phases of glacier retreat when ice cores do not melt and fluvial and other destructive processes remain ineffective in the permafrost environment. [ABSTRACT FROM AUTHOR]

In this study, the author explores the volumetrics of petroleum generation using a well constrained set of source rock and Kimmeridge Clay Formation petroleum samples at maturities covering the complete generation window from the North Sea. Densities of pure kerogen isolates were determined using density gradient centrifugation. Best estimates were derived for the composition of petroleum as a function of maturity. The PVTX properties of the petroleum were derived using PVTSim v.10. Combining the kerogen density data with the petroleum PVTX data, and placing these data into an algebraic mass balance scheme, the volume and pressure changes attendant upon petroleum generation were determined as a function of maturity. For source rock temperatures up to ∼130°C, the volume expansion is about 21% of the immature kerogen volume with an attendant pressure increase of about 10 MPa within the uncertainty of the methods in a closed system. Significant increases in volume, up to 71% with a concomitant pressure increase of about 33 MPa only occur at temperatures >130°C, when generated fluids have high gas-oil ratio. The results suggest that a completely closed source rock system can become overpressured during the main phase of oil generation. [ABSTRACT FROM AUTHOR]

This study presents a growth curve developed from direct and indirect growth rates of Rhizocarpon geographicum lichens from study sites on Mounts Baker, Rainier, Adams, and Hood in the northern Cascade Range of the western USA. Our observations of direct growth rates are based on 31 measurements of 11 lichens growing on different surfaces. This direct growth rate dataset is complemented by indirect growth rates based on measurements of the largest lichen observed on 20 different surfaces over 24-33-yr periods. The direct and indirect datasets produce statistically indistinguishable mean radial growth rates of 0.48 and 0.50 mm yr−1, respectively. Statistical analysis of zero and first order fits of our growth rate data suggests that lichen growth is best characterized by the average of our mean growth rate (zero order) models at 0.49 mm yr−1. Our revised growth curve for the study area extends the applicable range for dating rock surface in the study area to the seventeenth century, approximately 175 years longer than previous calibrated curves. [ABSTRACT FROM AUTHOR]

Chemical compositions and geochronological data utilising the laser ablation ICP-MS technique are presented for zircon megacrysts found in alluvial gem corundum deposits associated with Upper Cretaceous–Cenozoic alkali basalts in the Inverell district-New England field, New South Wales, eastern Australia. Three localities, Kings Plains, Swan Brook and Mary Anne Gully, produce gem-quality transparent dark brown and yellow zircon megacrysts, mostly under 10 mm in size. Although brown zircon shows relative enrichment in Hf and REE, there are no differences in relative transition metal concentrations between the colours. Chemical homogeneity within a single crystal indicates stable crystallisation conditions. The 206Pb/238U age of zircon megacrysts from these three localities define older and younger groups of 216–174 Ma and 45–37.7 Ma, respectively. The ϵHf values of zircon megacrysts from Kings Plains show +7.51±0.34 in the older group and +10.72±0.31 in the younger group. Swan Brook zircons give +11.54±0.47 and +8.32±0.58, and Mary Anne Gully zircons are +13.67±0.63 and +8.50±0.48, respectively. These zircons from New England alluvial gem deposits have two main formational events around Upper Triassic–Lower Jurassic and Eocene episodes. Most originated from lithospheric mantle and all were brought-up by later host basaltic magmas. [ABSTRACT FROM AUTHOR]

The article presents a paleontological study on the occurrence of the long-snouted crocodyliform fossil "Terminonaris" from the Woodbine Formation of Lewisville Lake in Denton County, Texas. It provides phylogenic description of the nasal of the fossil, and elaborates diagnostic characters of the genus specie which include the anterior terminus of premaxillae, the posterolateral process of squamosal, and the lateral termination of the paroccipital process. Meanwhile, it concludes the "Terminonaris" occur in marginal marine and offshore deposits due to its warm-temperate water along the margins of seaways.

The article presents a paleontological study of a hemigaleidae fossil, a small family of carcharhiniform sharks in Wadi Al-hitan, Fayum, Egypt. It notes that type and comparative material of such species was recovered from sites of the United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site. It states that the teeth of the hemigaleid were sorted into two tooth sets which showed strong but gradient monognathic heterodonty. Morphological features of the hemigaleidae's teeth are also discussed.

The article presents a paleontological study of a sauropod skin and a specimen of a second, unidentified skin type from the Upper Jurassic Morrison Formation in Mesa County, Colorado. It notes the physical characteristics of each specimen before carbon dating. It discusses a comparison between the two specimen after they have been carbonized. It mentions preservation methods of each specimen and how paleonenvironments affect fossils' condition. Photographs of specimens of carbonized dinosaur skin from the Mygatt-Moore Quarry, Upper Jurassic Morrison Formation are also provided.

Matthews, J.A. and Trenbirth, H.E., 2011. Growth rate of a very large crustose lichen (Rhizocarpon subgenus) and its implications for lichenometry. Geografiska Annaler, Series A: Physical Geography, 93, 27–39. The growth rate of an individual thallus of the Rhizocarpon subgenus with a current maximum diameter of 465 mm was measured directly over a 26‐year period at ca 5‐year intervals along 10 radii. Mean annual diametral growth rate was 0.48 mm yr−1 (the range between individual radii and time intervals was 0.02–1.54 mm yr−1). The southeasterly aspect of the lichen may have led to a higher growth rate in years that were relatively cool and dry. Combined with the growth rate of 18 smaller lichens at the site near the Haugabreen glacier in southern Norway, the data support a parabolic growth‐rate model. The corresponding growth curve, which is sigmoidal, indicates an age of about 1000 years for the very large lichen. Results also suggest that it may be possible to extend the temporal range of traditional (largest lichen) lichenometric dating in southern Norway. However, despite having been pointed out by R.E. Beschel in the 1950s, there is still an urgent need for further direct lichenometric data, for the monitoring of relatively large lichens and for a better understanding of the factors causing variability in growth rates. [ABSTRACT FROM AUTHOR]

The lithology of limestone from seven Neogene sites from the Indo-Pacific region, from the Salayar Limestone in South Sulawesi, Indonesia, the Yalam Limestone in East New Britain, Papua New Guinea (P.N.G.) and the Daliconi and Futuna Limestone members of the Tokelau Limestone Group on Vanua Balevu in the Lau Group, Fiji, is described. The ages of foraminiferal assemblages collected at all sites are compared with 87Sr/86Sr isotope ages of samples from the same locations. Combined geochemical and biostratigraphic dating indicates a late Miocene to Pliocene/Pleistocene age for sections in Indonesia, a middle Miocene age for sections in P.N.G., and middle to late Miocene ages for sections in Fiji. [ABSTRACT FROM AUTHOR]

A new series of radiocarbon and tree-ring dates from the Mimbres area of the Mogollon region has modified the accepted chronology in the area. Recent work in the Mogollon-Mimbres area has firmly established the existence of a plain ware pit house period dated about A.D. 200-550. The dates of phases between A.D. 550-1000 have been modified, and the termination of the Classic period is dated at A.D. 1150. The Mangas phase is dropped, and it is shown that black-on-white ceramics and puebloan architecture do not appear almost simultaneously as previously believed. These changes have implications for the investigation of past settlement subsistence and social interaction patterns in southwestern New Mexico. [ABSTRACT FROM AUTHOR]

One of the most significant topics in the history of Alpine geology involves the practice which began in the late eighteenth century of incorporating the sense of geohistory as recorded in the strata within the primarily structural classification of formations and mountains. Historical studies concerning this aspect in the scientific literature and unpublished primary sources related to the Alps and the pre-Alps from this period have shown that rocks and formations were then considered as central elements in a proto-stratigraphy or lithostratigraphy, which as yet was not based on the prominent use of fossils. This article presents an introductory overview of some pivotal eighteenth-century studies to suggest their role in the development of historical geology. [ABSTRACT FROM AUTHOR]

Charlotte Yonge placed religious belief at the centre of her world view, yet this did not prevent her from engaging with nineteenth-century geological theories traditionally associated with crises of faith, namely the discovery that the earth pre-dates the existence of humans by millions of years and that forms of life long extinct once populated its surface. Fossils, which call to mind both geological “deep time” and the extinction of species, figure prominently in her 1864 novel The Trial, and Yonge herself avidly collected fossils. Yonge represents fossils in The Trial as buried traces uncovered after an unfathomably long time, and this article will argue that they serve as metaphors for a divine providence which eventually reveals the truth, despite the apparent success of erroneous human judgement. Instead of symptoms of a deep religious anxiety, Yonge's fossils allowed Victorian readers to further appreciate the transcendence of God. [ABSTRACT FROM AUTHOR]

Lead isotope ratios were determined in clinopyroxene originating from Hungary and in a Japanese basalt standard (JB-2) by a single-collector inductively coupled plasma sector field mass spectrometer applying solution nebulization and laser ablation (LA) as sample introduction techniques. The solutions were prepared by dissolution of samples in a mixture of HF/HNO3 and isolation of analyte by Pb-selective crown ether resin. The separation of Pb from the matrix and other compounds lowered the contribution of the major interference (204Hg) to the counts of 204Pb to less than 1%. More than 94.5% and 98.4% of the Pb content of the clinopyroxene and JB-2 samples, respectively, could be collected on the resin. The relative standard deviations of the measured Pb isotope ratios obtained by solution technique changed between 0.3% and 0.5%. In the case of LA with repetition rate of 10 Hz and spot size of 100 µm these values were between 1.3% and 1.6%. [ABSTRACT FROM AUTHOR]

Here we present a series of six maps illustrating the distribution of end moraines in Far NE Russia. The maps are the first to systematically document the distribution of moraines across this region from the Verkhoyansk Mountains at the westernmost limit of our study area to the Chukchi Peninsula in the NE and to Kamchatka in the south, covering almost 4 million km2. Moraines were identified and mapped from analysis of satellite images and digital elevation model data. A total of 2173 moraines are identified, and we highlight some 197 more speculative features (perhaps moraines) that require further investigation. The distribution of moraines indicates that much of the region, now largely ice-free, was formerly occupied by glaciers centred upon the region's uplands and that glacier outlets were typically < 200 km in length. The maps demonstrate the usefulness of remote sensing to derive an improved understanding of the glacial history of this vast and isolated region, and we present them to stimulate further work and act as a systematic framework for targeted geochronometric dating. [ABSTRACT FROM AUTHOR]

The Miocene Stanislaus Group (Stanislaus, Calaveras, Tuolomne, Alpine and Mono counties, CA), composed of intercalated latite and quartz-latite (trachyandesite and trachyte/trachydacite) lavas and ignimbrites, provides an important marker for reconstructing the elevation history and tectonic development of the Sierra Nevada and Walker Lane. We present new 40Ar/39Ar geochronology and magnetostratigraphy indicating that the Stanislaus Group was emplaced in two pulses: (1) major outpouring of latite lavas at ca. 10.4 Ma and (2) ignimbrite eruptions alternating with lesser lava flow eruptions during ca. 9.4-9.8 Ma. These two events filled the ancestral Stanislaus River drainage in the region of the present Sierra Nevada crest, whereas the ignimbrite eruptions formed the Little Walker Caldera. Our new and previous results date these topographic changes and yield improvements to the Stanislaus Group stratigraphy. [ABSTRACT FROM AUTHOR]

Geochronology studies in South Australia were developed in three Adelaide institutions. (i) University of Adelaide: (ia) Department of Geology and Mineralogy, where four single chemical measurements were reported in 1923-1955 and 14 lead-alpha measurements in 1961; MSID Rb-Sr work began in 1972 followed by zircon U-Pb about 1980 and Sm-Nd later; (ib) luminescence equipment was developed in the Department of Physics and is used to date recent sediments. (ii) Flinders University, where alpha spectrometry disequilibrium dating of recent sediments was active during 1972-2000; and (iii) AMDEL, which supplied a variable commercial service of K-Ar, Rb-Sr and zircon dating during period 1972-1999. [ABSTRACT FROM AUTHOR]

John Harrison (1693-1776) is regarded as the father of chronometry. During his lifetime, he relentlessly pursued one of humankind's greatest and oldest challenges - that of finding the longitude at sea. In succeeding (according to the rules dictated by an Act of Parliament), he bequeathed to humankind the most accurate portable timekeeper the world had ever seen. It is a remarkable fact that his timekeeper, known today as H4, remains more accurate than the majority of expensive mechanical wristwatches manufactured today. Such accuracy required novel approaches to address the various difficulties that befall all mechanical watches, and Harrison overcame many of these with his own innovations. The reduction or elimination of friction is one such problem with clocks and watches, and from an early age Harrison demonstrated his mastery in this subject. This is typified by his choice of woods in his early clocks, and in later clocks by his 'grasshopper' escapement. In the 1750s, Harrison's attention switched from clocks to watches, necessitating a hardwearing, low friction material to be found for the pallets in the escapement of his timekeepers. He found these properties in diamond, and in utilizing this to great effect in H4's escapement, he became one of the first people to use diamond as a high-tech material. This paper describes a scientific investigation into the diamond pallets of H4 using Raman microscopy, X-ray diffraction and optical microscopy, to elucidate why diamond was used rather than a more conventional jewel such as ruby, and to gain some insight into how Harrison might have achieved their unconventional morphology. From the evidence presented here, together with evidence collected from primary sources, it is shown that his use of diamond as a hard, low friction material was nothing other than extraordinary, and should be regarded in the same high esteem as his other technological gifts to the world. [ABSTRACT FROM AUTHOR]

Holocene changes in terrestrial provenance and processes of sediment transport and deposition are tracked along a fjord-to-shelf transect adjacent to Vestfirdir, Iceland, using the magnetic properties ofmarine sediments. Magnetic susceptibility (MS) profiles of 10 cores (gravity and piston) were obtained onboard using a Bartington MS loop. Remanent magnetizations were measured at 1-cm intervals from u-channel samples taken from six cores on a cryogenic magnetometer. Between six and nine alternating field demagnetization steps were used to isolate the characteristic magnetization directions. The chronologies of the cores used in this study were determined from AMS 14C dates on mollusks and foraminifera and constrained by the regional occurrence of the 10,200 ± 60 cal yr. BP Saksunarvatn tephra. Correlative fluctuations in magnetic concentration are noted between the fjord and shelf sites, though these fluctuations are partiallymasked by regional variations in carbonate content. The onset of Neoglaciation is interpreted by changes in magnetic properties including an increase in mass magnetic susceptibility that began approximately 3000 cal yr. BP. The maximum angular deviation and the median destructive field (generally <20 mT) suggest that the natural remanent magnetization is carried by a coarse ferrimagnetite mineralogy, likely magnetite or titano-magnetite. Reproducible paleomagnetic inclination values are observed in several records, including a nearly vertical inclination around 8000 cal yr. BP, suggesting that the magnetic pole may have been proximal to Iceland, followed by an interval of much shallower inclination (6000-7000 cal yr. BP). [ABSTRACT FROM AUTHOR]

A review of the Valsequillo archaeological finds from the last century is given, such as the cranial remains (Dorenburg and Ostrander skulls), the engraved bone fragments, butchering marks, green bone fractures and flint points and scrapers. However, most of these finds are now missing. Their original dating is reviewed, along with the controversial Uranium Series and Fission Track dates from Hueyatlaco. Further relative dating techniques, such as the use of diatoms and bone assemblages, are discussed. Recently human and animal footprints from the Xalnene Ash at Toluquilla quarry have been described, mapped and dated by optically stimulated luminescence, and there has been new dating of the Valsequillo Gravels by AMS radiocarbon dating of molluscs and electron spin resonance of mammoth bone. The Xalnene Ash dates have proved controversial and the dating issues are reviewed. A suggested dating framework for the Valsequillo sequence in which the archaeological artefacts and footprints are found is given and all the stratigraphy with archaeological remains is considered to be Late Pleistocene in age. [ABSTRACT FROM AUTHOR]

The collection of papers in this issue of Mycologia documents considerable improvements in taxon sampling and phylogenetic resolution regarding the Fungal Tree of Life. The new data will stimulate new attempts to date divergences and correlate events in fungal evolution with those of other organisms. Here, we review the history of dating fungal divergences by nucleic acid variation and then use a dataset of 50 genes for 25 selected fungi, plants and animals to investigate divergence times in kingdom Fungi. In particular, we test the choice of fossil calibration points on dating divergences in fungi. At the scale of our analysis, substitution rates varied without showing significant within-lineage correlation, so we used the Langley-Fitch method in the R8S package of computer programs to estimate node ages. Different calibration points had a dramatic effect on estimated divergence dates. The estimate for the age of the Ascomycota/Basidiomycota split was 1 808 000 000 y ago when calibrated assuming that mammals and birds diverged 300 000 000 y ago, 1 489 000 000 y ago when calibrated assuming that the 400 000 000 y old fungal fossil Paleopyrenomycites devonicus represents Sordariomycetes and ∼400 000 000 y ago when calibrated assuming 206 000 000 y ago for the plant eudicot/monocot divergence. An advantage of a date of ∼400 000 000 y ago for the Ascomycota/Basidiomycota divergence is that the radiation of fungi associated with land plants would not greatly precede the earliest land plant fossils. Acceptance of ∼400 000 000 y ago for the Ascomycota /Basidiomycota split would require that P. devonicus be considered a deeply branching Ascomycota. To improve on current estimates of divergence times, mycologists will require calibration points from within groups of fungi that share similar substitution rates. The most useful calibration is likely to depend on the discovery and description of continuous records of fossil fungi, or their spores, that show recognizable shifts in morphology. [ABSTRACT FROM AUTHOR]

Russian Pomor people used Spitsbergen as a hunting and trapping area for over 300 years, from the early sixteenth century until the mid-nineteenth century. The early dating of Pomor activity is discussed with respect to written sources, dendrochronology, epigraphy, direct dating and geomorphological relationships. [ABSTRACT FROM AUTHOR]

A method is presented for quantifying the degree of edge roundness of large crystalline boulders using a simple instrument. The method utilises the transition due to granular disintegration from sharp to rounded boulder edges, so that the degree of edge roundness is a function of time and can be used as a relative dating tool. Edge roundness can be precisely measured in the field if strict morphological criteria are adhered to when selecting boulders to measure. Roundness can be expressed as a length measurement between fixed points on adjacent facets, as a normalised index, or as a radius of curvature. Boulder edge-roundness was employed to resolve uncertainty over the extent of the ‘Loch Lomond Stadial’ (LLS) glacier in the North-east Corrie of Lochnagar. Small but significant differences in edge roundness between two sets of moraine ridges indicate that the LLS glacier was smaller than that mapped by Sissons & Grant (1972). The moraine they ascribed to the LLS relates to an earlier advance within Late Devensian time. [ABSTRACT FROM AUTHOR]

In the western part of the Mt Isa Inlier one of the most obvious lithostratigraphic correlations is the Torpedo Creek Quartzite (Lawn Hill Platform) and the Warrina Park Quartzite (Leichhardt River Fault Trough). These two sand bodies form the basal lithostratigraphic unit of their respective groups – McNamara and Mt Isa – and crop out as easily mappable, prominent ridges of white quartzite. Correlation of these sand bodies forms the linchpins for lithostratigraphic subdivision in the region. To test this correlation a 2000&ThickSpace;m-thick stratigraphic interval around these two quartzite units was analysed using two modern techniques. A sequence stratigraphic analysis, which included detailed surface gamma-ray logging, was undertaken at 20 measured sections over an area of about 18 000&ThickSpace;km 2 to identify and correlate important stratal surfaces. Complementary high precision U–Pb SHRIMP dating of tuffaceous intervals was also done to provide independent control for the resulting new subdivisions of the section. The sequence analysis and SHRIMP dating of these units and the underlying Surprise Creek Formation demonstrate major miscorrelations in the current lithostratigraphy. SHRIMP dating helps to define a major unconformity with up to 20 million years of missing rock record: rocks above the surface are around 1670–1660 Ma, whilst those below are around 1690 Ma. Although 1:100 000 lithostratigraphic mapping enabled the recognition of an unconformity at the base of the Mt Isa and McNamara Groups, in the majority of cases this surface does not correlate with the major lithostratigraphic boundary with which it was associated. In consequence this unconformity and supersequence boundary remains unrecognised in most areas. The consequences of such miscorrelations are inadequate and inaccurate reconstructions of basin geometry and stratigraphic architecture, and have important economic implications when searching for stratabound base metals. [ABSTRACT FROM AUTHOR]

In principle, when 1,1-dichloroethylene (DCE) is formed from the hydrolysis of 1,1,1-trichloroethane (TCA), the ratio of DCE to TCA can be used to determine how long hydrolysis has been occurring and, consequently, the age of a TCA release to groundwater. The rate of hydrolysis appears to depend only on groundwater temperature, and sorption does not appear to have a significant effect on the hydrolysis rate. This article focuses on the uncertainties and biases in estimating the age of a TCA release from DCE/TCA ratios. Two methods are examined: (1) the use of one-time ratio measurements together with a laboratory-derived hydrolysis rate constant and (2) the use of time series data collected over a number of years. When the uncertainty in concentration measurements is small, the principal uncertainty for one-time measurements is due to the uncertainty in estimating the rate of hydrolysis at groundwater temperatures from laboratory data. For one-time measurements, we estimate 95% confidence levels for time estimates under favorable conditions of about ±25%. When time series data are available, using these data may be more or less accurate. The principal source of uncertainty then is due to uncertainty in concentration measurements. In interpreting field data, the age obtained should be recognized as an average based on when contact between water and TCA began. This may be different than a spill date for pure phase spills of TCA. Under some circumstances time estimates can be made when biodegradation of TCA as well as hydrolysis occurs. [ABSTRACT FROM AUTHOR]