Search

Cooperation among kin is common in animal societies. Kin groups may form by individuals directly discriminating relatives based on kin recognition cues, or form passively through natal philopatry and limited dispersal. We describe the genetic landscape for a primitively eusocial wasp, Polistes dominula, and ask whether individuals choose cooperative partners that are nearby and/or that are genetic relatives. Firstly, we genotyped an entire sub-population of 1361 wasps and found genetic structuring on an extremely fine scale: the probability of finding genetic relatives decreases exponentially within just a few meters of an individual’s nest. At the same time, however, we found a lack of genetic structuring between natural nest aggregations within the population. Secondly, in a separate dataset where ~2000 wasps were genotyped, we show that wasps forced experimentally to make a new nest choice tended to choose new nests near to their original nests, and that these nests tended to contain some full sisters. However, a significant fraction of wasps chose nests that did not contain sisters, despite sisters being present in nearby nests. Although we cannot rule out a role for direct kin recognition or natal nest-mate recognition, our data suggest that kin groups may form via a philopatric rule-of-thumb, whereby wasps simply select groups and nesting sites that are nearby. The result is that most subordinate helpers obtain indirect fitness benefits by breeding cooperatively.

Humans introduced paper mulberry (Broussonetia papyrifera) from Taiwan into the Pacific over 5000 years ago as a fiber source to make barkcloth textiles that were, and still are, important cultural artifacts throughout the Pacific. We have used B. papyrifera, a species closely associated to humans, as a proxy to understand the human settlement of the Pacific Islands. We report the first genetic analysis of paper mulberry textiles from historical and archaeological contexts (200 to 50 years before present) and compare our results with genetic data obtained from contemporary and herbarium paper mulberry samples. Following stringent ancient DNA protocols, we extracted DNA from 13 barkcloth textiles. We confirmed that the fiber source is paper mulberry in nine of the 13 textiles studied using the nuclear ITS-1 marker and by statistical estimates. We detected high genetic diversity in historical Pacific paper mulberry barkcloth with a set of ten microsatellites, showing new alleles and specific genetic patterns. These genetic signatures allow tracing connections to plants from the Asian homeland, Near and Remote Oceania, establishing links not observed previously (using the same genetic tools) in extant plants or herbaria samples. These results show that historic barkcloth textiles are cultural materials amenable to genetic analysis to reveal human history and that these artifacts may harbor evidence of greater genetic diversity in Pacific B. papyrifera in the past.

The Geological Society of America Bulletin was an early home for quantitative geomorphology research. Although geomorphology papers are not uniformly the highest cited papers in the Bulletin, many show ‘delayed recognition’—they garner only few citations directly after publication, before suddenly being widely and numerously cited (sometimes decades after publication). I focus here on (1) algorithmically detecting cases of delayed recognition in geomorphology literature from the Bulletin and (2) providing insight into why delayed recognition occurred for these papers.

The northern Bay of Bengal velocity-depth profiles do not follow the velocity-depth curve of the North Atlantic volcanic margins, and only partially the Kerguelen velocity-depth curves. Deep seismic refraction and reflection profiles acquired across the Hatton bank and Feroes ridge show that the melt is intruded into the lower thinned continental crust as sills, which cross-cut the continental fabric rather than underplating as it was often assumed in the past. Compared with the SCS northern margin proxy, we still suggest that the BoB crust is thinned continental crust intruded by post-rifting volcanics, as also shown by the interpretation of the numerous high-quality deep MCS profiles we collected there. What was supposed to be underplating might be sills intruded through the lower thinned continental crust.

The methods of open channel hydraulics, designed to calculate the capacity of canals and river channels, can be used to determine the hydraulic and hydrological characteristics of ancient river channels. Large available empirical data allows calculations of channel capacity with an accuracy of 10–15%. The same accuracy is possible for the calculation of bankfull paleochannel discharge in the conditions of correct choice of the cross-section and the reconstruction of its morphometry: altitude of floodplain edges, paleochannel width at bankfull stage, average depth and surface slope of the flow. Morphometric characteristics of ancient channels and particle size distribution of alluvial deposits are obtained by detailed coring at channel cross-sections. In modern rivers, straight channel reaches without backwater effects, flow divergence or convergence are usually selected for the calculation of discharges with Chezy formula. Given that, coring of meandering paleochannels is rational to be organized at straight insertions between two adjacent bends. These reaches correspond to shallow crosses with low longitudinal and lateral flow non-uniformity and negligible backwater effects at high water levels. The most reliable results can be obtained for the non-deformable (slightly deformable) paleochannels. The uncertainty in the estimation of ancient discharges increases significantly for deformable paleochannels. Changes in the paleochannel cross-section shape during its conservation, the uncertainty in the determination of textural contacts in alluvium and filling deposits, errors in determining of paleochannel slope lead to an increase in the total error of a palaeo-discharge estimate. The conversion from the bankfull discharge to a discharge of another frequency (i.e. to annual or mean maximum discharge) is processed with the help of empirical equations. This reduces significantly the accuracy of the calculations, since the empirical relationships are characterized by implicit errors, which are difficult to identify and reduce. Therefore, the accuracy of the hydraulic methods for estimating the annual discharge is about the same as that of the morphometric methods (regime equations), i.e. about 30–40%.

Digital photogrammetry has experienced rapid development regarding the technology involved and its ease of use over the past two decades. We revisit the work of Jim Chandler who in 1999 published a technical communication seeking to familiarise novice users of photogrammetric methods with important theoretical concepts and practical considerations. In doing so, we assess considerations such as camera calibration and the need for photo-control and check points, as they apply to modern software and workflows, in particular for structure-from-motion (SfM) photogrammetry. We also highlight the implications of lightweight drones being the new platform of choice for many photogrammetry-based studies in the geosciences. Finally, we present three examples based on our own work, showing the opportunities that SfM photogrammetry offers at different scales and systems: at the micro-scale for monitoring geomorphological change, and at the meso-scale for hydrological modelling and the reconstruction of vegetation canopies. Our examples showcase developments and applications of photogrammetry which go beyond what was considered feasible 20 years ago and indicate future directions that applications may take. Nevertheless, we demonstrate that, in-line with Chandler’s recommendations, the pre-calibration of consumer-grade cameras, instead of relying entirely on self-calibration by software, can yield palpable benefits in micro-scale applications and that measurements of sufficient control points are still central to generating reproducible, high-accuracy products. With the unprecedented ease of use and wide areas of application, scientists applying photogrammetric methods would do well to remember basic considerations and seek methods for the validation of generated products.

The article under discussion, whilst providing generalized accounts of the effects of waterflows in karstic formations, fails, in the opinion of this respondent, to substantiate the claims that an immediate threat is posed to the continued preservation of the monuments at Tāq-e Bostān, the focus of this response.

Starting from the model proposed by the authors to analyze the time-evolution of bedforms growing on the surface of an initially flat sand bed, the present study explores associated features of the bedform growth processes, including (i) mechanisms of growth, (ii) evolution of the bedform-induced drag, (iii) transition to antidunes, and (iv) non-equilibrium bedload sediment transport.

Arnold, L. J. & Roberts, R. G. 2011: Paper I – Optically stimulated luminescence (OSL) dating of perennially frozen deposits in north−central Siberia: OSL characteristics of quartz grains and methodological considerations regarding their suitability for dating. Boreas, Vol. 40, pp. 389–416. 10.1111/j.1502-3885.2011.00209.x. ISSN 0300−9483. Optically stimulated luminescence (OSL) dating of coarse-grained quartz is increasingly being used as the main chronological tool in late Quaternary palaeoenvironmental reconstructions of Siberia. However, relatively little information has been published on the suitability of OSL dating for the various types of perennially frozen sediments found in this region. Here we provide a systematic examination of the quartz luminescence characteristics of 21 perennially frozen samples from the Taimyr Peninsula and adjacent coastal lowlands of north-central Siberia, and discuss their implications for the reliability of single-grain and multi-grain OSL chronologies in such contexts. The results of this study suggest that the quartz luminescence characteristics of these samples are, in principle, favourable for OSL dating but, in practice, require that a series of validation checks are made of the chosen experimental conditions. If these tests are satisfied, then reliable OSL chronologies should be obtained for sedimentary deposits in this region. Importantly, however, the single-grain and multi-grain aliquot equivalent dose (De) distribution characteristics for our samples reveal that there are advantages in targeting certain types of depositional settings for OSL dating studies of Siberian sediments. We also show that samples from the same depositional settings, and even from the same sites, do not necessarily display similar De distribution characteristics. The latter complication favours the use of single-grain analysis to unravel the bleaching and burial histories of young (mid- to late Holocene) sediments in these Arctic environments.

Colluvium and debris-flow deposits differ from each other and from glacial till and glacial outwash deposits in Durango, CO, in terms of sedimentological properties evaluated using laboratory testing. Testing included grain-size analysis, Atterberg limits, specific gravity, visual angularity, and uncompacted void content (UVC). Grain-size analysis showed that colluvium, glacial deposits, and debris-flow deposits had different grain-size distributions (GSDs) that occupied fields on a GSD graph with some overlap. Debris-flow deposits had the most gravel-sized grains, and colluvium had the most silt- and clay-sized grains, while glacial till and glacial outwash had very similar GSDs between colluvium and debris-flow deposits. Comparisons of angularity to gravel-to-fines (G/F) ratio provided a second graphical method for discriminating between debris-flow, colluvium, and glacial deposits. Generally, colluvium and debris-flow deposits were more angular than glacial till and outwash. Additionally, several linear correlations were recognized between lithology of grains and sedimentological and geotechnical properties, the most significant of which were: (1) The angularity of gravel in glacial till and outwash was positively correlated to sandstone gravel content, (2) the plasticity index of outwash fines was positively correlated to the metamorphic gravel content, (3) the amount of outwash fines was positively correlated to sandstone and metamorphic gravel content, while it was negatively correlated to carbonate gravel content, and (4) rounded and sub-rounded gravel content in outwash was positively correlated to carbonate and extrusive igneous gravel content. This study provides insight into the geomechanical differences between depositional mechanisms in similar semiarid environments.

At retreating margins of the Antarctic Ice Sheet, there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice-covered. This paper presents a site description of one of these lakes, Hodgson Lake, situated on southern Alexander Island, west of the Antarctic Peninsula (72° 00.549′ S, 68° 27.708′ W). First, we describe the physical setting of the lake using topographic and geomorphological maps. Second, we determine local ice sheet deglaciation history and the emergence of the lake using cosmogenic isotope dating of glacial erratics cross-referenced to optically stimulated luminescence dating of raised lake shoreline deltas formed during ice recession. Third we describe the physical and chemical limnology including the biological and biogeochemical evidence for life. Results show that the ice mass over Hodgson Lake was at least 295 m thick at 13.5 ka and has progressively thinned through the Holocene with the lake ice cover reaching an altitude of c. 6.5 m above the present lake ice sometime after 4.6 ka. Thick perennial ice cover persists over the lake today and the waters have remained isolated from the atmosphere with a chemical composition consistent with subglacial melting of catchment ice. The lake is ultra-oligotrophic with nutrient concentrations within the ranges of those found in the accreted lake ice of subglacial Lake Vostok. Total organic carbon and dissolved organic carbon are present, but at lower concentrations than typically recorded in continental rain. No organisms and no pigments associated with photosynthetic or bacterial activity were detected in the water column using light microscopy and high performance liquid chromatography. Increases in SO4 and cation concentrations at depth and declines in O2 provide some evidence for sulphide oxidation and very minor bacterial demand upon O2 that result in small, perhaps undetectable changes in the carbon biogeochemistry. However, in general the chemical markers of life are inconclusive and abiotic processes such as the diffusion of pore waters into the lake from its benthic sediments are far more likely to be responsible for the increased concentrations of ions at depth. The next phases of this research will be to carry out a palaeolimnological study of the lake sediments to see what they can reveal about the history of the lake in its subglacial state, and a detailed molecular analysis of the lake water and benthos to determine what forms of life are present. Combined, these studies will test some of the methodologies that will be used to explore deep continental subglacial lakes.

We present a detailed cryostratigraphic reconstruction of the degradation and recovery of near-surface permafrost in the southern Klondike goldfields, central Yukon Territory. Two ice-rich layers are recognized in near-surface permafrost and attributed to thermal impacts following vegetation disturbance. At an undisturbed forest site, the base of the modern active layer is stable. At an adjacent site, where a late twentieth century disturbance of surface vegetation and permafrost degradation occurred, there is evidence of recovery in the form of aggradation (upward shift) of the permafrost table following limited vegetation succession. Underlying both the undisturbed forest and the late twentieth century disturbance is an older thaw unconformity corresponding to a thaw depth of ∼2 m, likely associated with early twentieth century (gold rush era) impacts. Field and air photo surveys allow identification of the nature of the disturbances, while a chronology of the surface disturbance has been established using age estimates from tree rings, and the presence of tritium and post-bomb 14C from organic samples within aggradational ice. Collectively, these data underscore the importance of vegetation cover in maintaining ground temperatures in the discontinuous permafrost zone and suggest that, at least at the study site in recent decades, permafrost shows the potential to recover from disturbance in the modern climatic regime of the region.

The ∼470 Ma Ammonoosuc Volcanics of the Bronson Hill terrane of New Hampshire have back-arc basin basalt compositions. Major and trace element compositions compare favorably to coeval volcanic rocks in the Miramichi Highlands of New Brunswick and the Munsangan and Casco Bay volcanics of Maine, back-arc basin basalts of known peri-Gond- wanan origins. Additionally, the Ammonoosuc Volcanics have Nd and Pb isotopic compositions indicative of peri-Gond- wanan provenance. Thus, the Ammonoosuc Volcanics correlate with Middle Ordovician, peri-Gondwanan, Tetagouche- Exploits back-arc rocks of eastern New England and Maritime Canada. This correlation indicates that the Red Indian Line, the principle Iapetus suture, lies along the western margin of the Bronson Hill terrane. However, the younger (∼450 Ma) Oliverian Plutonic Suite rocks that intruded the Ammonoosuc Volcanics, forming domes along the core of the Bronson Hill anticlinorium, have Laurentian isotopic signatures. This suggests that the Ammonoosuc Volcanics were thrust westwardly over the Laurentian margin, and that Laurentian basement rocks are present under the Bronson Hill terrane. A plausible ex- planation for these relationships is that an easterly dipping subduction zone formed the Ammonoosuc Volcanics in the Tetagoughe-Exploits oceanic tract, just east of the coeval Popelogan arc. With the closure of the Iapetus Ocean, this terrane was thrust over the Laurentian margin. Subsequent to obduction of the Ammonoosuc Volcanics, subduction polarity flipped to the west, with the Oliverian arc resulting from a westerly dipping subduction zone that formed under the Taconic Orog- eny-modified Laurentian margin. Resume : Les roches volcaniques Ammonoosuc, ∼470 Ma, du terrane de Bronson Hill au New Hampshire ont des compo- sitions de bassins basaltiques d'arriere-arc. Les compositions en elements majeurs et traces se comparent favorablement aux roches volcaniques contemporaines des terres hautes de Miramichi au Nouveau-Brunswick et les roches volcaniques de Munsangan et de Casco Bay au Maine, des bassins basaltiques d'arriere-arc d'origine peri-gondwanienne connue. De plus, les roches volcaniques Ammonoosuc ont des compositions d'isotopes de Nd et de Pb qui indiquent leur provenance peri- gondwanienne. Ainsi, les roches volcaniques Ammonoosuc sont correlees avec les roches d'arriere-arc Tetagouche-Exploits, Ordovicien moyen peri-Gondwana, de l'est de la Nouvelle-Angleterre et des provinces maritimes canadiennes. Cette correla- tion signifie que la ligne Red Indian, la principale suture Iapetus, se situe le long de la bordure ouest du terrane de Bronson Hill. Toutefois, les roches de la suite plutonique Olivierian, plus jeune (∼450 Ma), formant des domes le long du cœur de l'anticlinorium Bronson Hill, ont des signatures isotopiques laurentiennes. Cela suggere que les roches volcaniques Ammo- noosuc aient ete chevauchees vers l'ouest par-dessus la bordure laurentienne et que les roches du socle laurentien se retrou- vent sous le terrane de Bronson Hill. Une explication plausible pour ces relations est qu'une zone de subduction a pendage vers l'est a forme les roches volcaniques Ammonoosuc dans l'etendue oceanique Tetagouche-Exploits, tout juste a l'est de l'arc Popelogan contemporain. Avec la fermeture de l'Ocean Iapetus, ce terrane a ete chevauche par-dessus la bordure lau- rentienne. Apres l'obduction des roches volcaniques Ammonoosuc, la polarite de la subduction a bascule vers l'ouest; l'arc Oliverian proviendrait d'une zone de subduction a faible pendage vers l'ouest qui s'est formee sous la bordure laurentienne modifiee par l'orogenese taconienne. (Traduit par la Redaction)

This study is centred on the Bonaparte Lake map area located in the southern Interior Plateau of south-central British Columbia. The reconstruction of the Late Wisconsinan glacial history of this part of the southern sector of the Cordilleran Ice Sheet incorporates (i) the analysis and interpretation of landforms of various scales, (ii) the sedimentology and stratigraphy of glacial sediments, and (iii) the geochemical and mineralogical composition of till and analysis of regional glacial dispersal of these components. The onset of the last glacial event was initiated by ice advancing westerly and southwesterly into the study area from an alpine source region located in the Cariboo Mountains. As glaciation intensified, ice from the Coast Mountains coalesced with the Cariboo Mountain ice over the Interior Plateau and developed into an ice divide around 52° north latitude, which resulted in ice flow to be diverted to a southerly direction over the study area. The two dominant ice-flow directions produced palimpsest dispersal that was measured by three tracers in till including thorianite grains and terbium concentrations in the heavy mineral fraction, and granitoid pebble percentage. The two main phases of ice flow identified within our study area have significant implications for mineral exploration that uses mineral tracing in glacial sediments, especially in the area underlain by the highly prospective Quesnel Terrane.

Combined mapping, U–Pb isotope dilution – thermal ionization mass spectrometry (ID–TIMS) geochronology and geochemical studies in Harvey-Cardiff domain in the western Composite Arc Belt reveal the presence of a long-lived magmatic–metamorphic history between 1290 and 1030 Ma. Following intrusion of gneissic tonalite of the Anstruther and Burleigh gneiss complexes at ca. 1290 Ma, diorite of the Salmon Burn intrusive complex was emplaced at 1242.1 ± 1.1 Ma. A potassium-feldspar megacrystic monzogranite in the Salerno Creek deformation zone that forms the boundary between Harvey-Cardiff domain and Bancroft terrane was emplaced at 1211.3 ± 1.5 Ma, similar to the 1220 ± 1.6 Ma old Junction pluton and a previously reported age of ca. 1229 Ma from another Methuen suite granite in the domain. All three ages are 20 to 30 million years younger than Methuen suite ages elsewhere in the Composite Arc Belt (1250–1240 Ma). Deformation along the Salerno Creek deformation zone is constrained between 1211 Ma, the age of the megacrystic monzogranite, and 1050 Ma, the age of titanite grains from the Salmon Burn intrusive complex and a late alkalic dike. A monzogranite of the newly recognized Catchacoma granite suite yielded an age of 1067 ± 3.7 Ma, similar to the 1059.2 ± 1.6 Ma age obtained from the Cavendish pegmatite vein. These ages suggest a temporal link between late granite and pegmatite emplacement in Harvey-Cardiff domain. Metamorphic zircon, monazite, and titanite ages fall into three clusters (1082–1070, 1063–1045, and 1037–1030 Ma) and may represent a protracted metamorphic event or reflect distinct pulses during the Ottawan orogeny.

The brightest geoscience students competed for the best student submission to the EAGE Annual Meeting 2015. Competition was fierce, but after much deliberation three papers have been chosen to be presented as part of the EAGE Technical Programme in Madrid.

U–Pb baddeleyite ages and paleomagnetic poles obtained for dykes on Devon Island and Ellesmere Island in the Canadian Arctic and the Thule region of Greenland show that they are associated with the Franklin magmatic event. This study is the only one devoted to Franklin igneous rocks where a primary paleomagnetic remanence and U–Pb age have been obtained from the same rocks. Ages from this study range from 721 to 712 Ma, but paleomagnetic directional data show no clear age progression. The paleomagnetic poles from each of the two regional subsets are significantly different at the 95% confidence level from paleomagnetic results previously published for the Franklin event in the Canadian Shield. The difference in the pole locations can be accounted for, to first approximation, by a simple model of early Cenozoic block rotations among the North American plate, Greenland, and a hypothesized ancient microplate comprising Ellesmere, Devon, Cornwallis, and perhaps Somerset islands. A new grand-mean paleopole for the Franklin event, including restoration of Greenland and the proposed “Ellesmere microplate” to North America, is located at (8.4°N, 163.8°E, A95 = 2.8°, N = 78 sites) and is a key pole for Neoproterozoic supercontinent reconstructions.

Reply to the comment of Pedoja et al. by Maouche, S., Meghraoui, M., Morhange, C., Belabbes, S., Bouhadad, Y. and Haddoum, H. on the published paper: Maouche, S., Meghraoui, M., Morhange, C., Belabbes, S., Bouhadad, Y. and Haddoum, H., 2011, Active coastal thrusting and folding, and uplift rate of the Sahel anticline and Zemmouri earthquake area (Tell Atlas, Algeria), Tectonophysics, 509 (2011) 69–80 Said Maouche, Mustapha Meghraoui⁎, Christophe Morhange, Samir Belabbes⁎⁎, Youcef Bouhadad, Hamid Haddoum

The relatively subdued topography of British Columbia’s northern interior plains does not reflect the irregular, buried bedrock surface. Many areas have been deeply incised by preglacial rivers that have subsequently filled with a succession of Quaternary sediments. In this study, oil and gas petrophysical logs, drill chip samples, water well logs, and surficial and bedrock outcrop maps were used to model the bedrock topography of the Fontas map sheet (NTS 94I). The modelled data produced several depressions that are interpreted to be paleovalleys incised into the soft Cretaceous shale of the Fort St. John Group. Understanding the geometry, thickness, and stratigraphy of the drift has considerable safety and resource management implications as artesian aquifers and natural gas were encountered in the drift during oil and gas well drilling. Four major paleovalleys are suggested. The most dominant paleovalley (Kotcho–Hoffard Paleovalley) is located south of the Etsho Plateau and trends west-southwest across the map area. A second depression occurs within the loop of the Hay River and may be a tributary of the Kotcho–Hoffard Paleovalley that links with the Rainbow Paleovalley in Alberta. A third paleovalley is mapped south of the Sahtaneh River (Kyklo Creek Paleovalley) and is either a tributary to, or crosscuts the Kotcho–Hoffard Paleovalley. The Niteal Creek Paleovalley is located between the Fontas and Sikanni Chief rivers. Its geometry is speculative as there are sparse data, but it may be a tributary of the Kotcho–Hoffard Paleovalley.

Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ± 2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river.

A discussion on papers “Nature of a major tectonic discontinuity in the Svecofennian province of northern Sweden” by Rutland et al. (PR 112, 211-237, 2001) and “age of deformation episodes in the Palaeoproterozoic domain of northern Sweden, and evidence for a pre-1.9 Ga crustal layer” by Rutland et al. (PR 112, 239-259, 2001).