Macrostructural analysis : unravelling polyphase glacitectonic histories

Many Pleistocene glacial profiles look extremely simple, comprising till, or glacitectonite, overlying older sediments or bedrock (Figure 4.1). In more complex sequences the till may itself be overlain by younger sediments laid down as the ice retreated or during a completely separate, later phase of advance. Macroscopically, subglacial traction tills (Evans et al., 2007) are typically massive, unstructured deposits suggesting that it should be relatively straightforward to unravel the glacitectonic deformation history recorded by the sequence. Many reconstructions do indeed look very simple, slabs of sediment have been tilted and stacked and then overridden by the glacier to cap the structure with till. Added to this is the use of vertical exaggeration which makes the whole structure look like alpine tectonics (for an example see fig. 5 in van Gijssel, 1987). Dropping the exaggeration led to the recognition that actually we were looking at much more horizontal structures, i.e. overriding nappes and not imbricated slabs (van der Wateren, 1987). Traditionally (van der Meer, 1987) glaciotectonics was thought to relate to large structures like big push moraines and not to smaller structures like drag structures underneath tills (Figure 4.2), let alone to the tills themselves. With the notion that deforming bed tills are tectonically and not sedimentologically structured and could be regarded as tectomicts (Menzies et al., 2006), comes the realisation that glacitectonics happens across a wide range of scales, from the microscopic to tens of kilometres. Only by realising the full range of glaciotectonic scales can we hope to understand the processes

Understanding resource choice at the transition from foraging to farming: An application of palaeodistribution modelling to the Neolithic of the Konya Plain, south-central Anatolia, Turkey

© 2018 Elsevier Ltd The role of the environment in shaping agricultural origins is still not fully understood, despite a century of debate on this topic. Comparison of the expected prevalence of a resource in the landscape with actual archaeological presence of the same resource can provide a metric for assessing resource choice in prehistory. However, the palaeoenvironmental data that would allow resource choice to be evaluated in this way are rarely available. Species Distribution Modelling (SDM) techniques allow independent palaeoenvironmental datasets to be computed, which when compared to actual species’ presence at sites as attested by archaeological datasets, can provide data on resource choice. Following recent calls for SDM to be applied more widely in archaeological contexts, we outline a simple method for predicting the presence of plant species in prehistory using modern analogues and palaeoclimatic datasets. These modelled distributions provide an independent dataset for comparison with archaeological data, thus providing a window into human resource choice in prehistory. We outline the method with specific reference to the transition from foraging to farming in the Neolithic of Central Anatolia, but the method could be applied to any period or region. We have used exclusively open source data and provided all code in our online supplementary materials, so that our method can be utilized by researchers interested in human resource choice in any region of the world and any period

Will farmers work together for conservation? The potential limits of farmers’ cooperation in agri-environment measures

There is growing concern that Agri-environment Schemes (AESs) may not be effective in conserving the countryside. Particular concern has arisen around whether the current approach of individual, farm-level, AES agreements are sufficient to offer landscape-scale environmental protection and enhancement. Whilst recent additions to AESs have sought to encourage more joined-up thinking by offering payments to farmers to form collective agreements, uptake is low and there is very little known about farmers’ (non)resistance to such collective conservation. Drawing on in-depth qualitative research with 74 farms across 5 sites in the UK, this paper provides new data on the barriers to farmers’ uptake of collective AESs and offers a new formulation of how we understand farming cooperation. The paper advances Bourdieusian-inspired ideas of the cultural construct of ‘good farming’ by synthesising these with recent reconceptualizations of ‘trust’ in order to provide a more contextually grounded and temporally-inflected understanding of farmers’ cooperative activities. The findings reveal that whilst working relations between farmers are often collegiate, and in places collective, several watershed events over past decades have led to a shift from community-level to process-based (peer-to-peer) trust and a move toward land management being depicted as a squarely individual rather than collective issue. Conceptually, the paper moves beyond the current limitation of viewing trust, and the associated development of social capital – seen as a prerequisite for more collective AESs – as cumulative and one-directional to highlighting their multiple, issue-specific, nature which may become eroded and (re)developed over time. Alongside this, the paper offers a new way of understanding the good farmer by shifting the focus from the individual farm/farmer level to a more fine-grained and contextualised issue-centered notion of good farming. This is then used to explain the seeming reluctance of land holders, evidenced in official statistics, to engage in collective AESs

Postglacial succession of caddisfly (Trichoptera) assemblages in a central European montane lake

The Bohemian Forest lakes, situated along the Czech-German-Austrian border, were strongly affected by atmospheric acidifi- cation between the 1950s and the late 1980s. The subsequent chemical recovery of the lake water should precede and enable a biological recovery, including changes in caddisfly (Insecta: Trichoptera) assemblages. Nevertheless, local pre-acidification data and detailed knowledge of the lake district history are missing, making evaluation of lake recovery difficult. We performed high-resolution analysis of caddisfly remains in a 2.2 m long sediment profile from Prášilské Lake covering the complete history of the lake-catchment evolution. Caddisfly larvae are good indicators of environmental conditions and their subfossil remains are well preserved in unconsolidated waterlaid sediments. A total of 10 caddisfly morpho-taxa were found providing a record from 11,400 cal. yr. BP to the present. With the exception of Athripsodes aterrimus, all identified species are currently present in the Bohemian Forest glacial lakes or their inflow streams but not all of them are documented in Prášilské Lake. The caddisfly fauna consisted of acid-resistant, acid-tolerant and eurytopic species since the Early Holocene. Based on our results, the acid, dystrophic state of Prášilské Lake has been occurring since the lake formation. We conclude that the first signs of natural acidification appeared not later than during the Holocene onset in the Bohemian Forest region. Furthermore, we did not detect any abrupt changes in the species composition connected to the period of anthropogenic acidification during the twentieth century. This study provides for the first time a record of postglacial succession of caddisfly assemblages in a central European mountain lake

The geomorphology of the Anthropocene:emergence, status and implications

This is the peer reviewed version of the following article: BROWN, A.G. ... et al, 2017. The geomorphology of the Anthropocene: emergence, status and implications. Earth Surface Processes and Landforms, 42(1), pp.71-90., which has been published in final form at http://dx.doi.org/10.1002/esp.3943. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The Anthropocene is proposed as a new interval of geological time in which human influence on Earth and its geological record dominates over natural processes. A major challenge in demarcating the Anthropocene is that the balance between human-influenced and natural processes varies over spatial and temporal scales owing to the inherent variability of both human activities (as associated with culture and modes of development) and natural drivers (e.g. tectonic activity and sea level variation). Against this backdrop, we consider how geomorphology might contribute towards the Anthropocene debate focussing on human impact on aeolian, fluvial, cryospheric and coastal process domains, and how evidence of this impact is preserved in landforms and sedimentary records. We also consider the evidence for an explicitly anthropogenic geomorphology that includes artificial slopes and other human-created landforms. This provides the basis for discussing the theoretical and practical contributions that geomorphology can make to defining an Anthropocene stratigraphy. It is clear that the relevance of the Anthropocene concept varies considerably amongst different branches of geomorphology, depending on the history of human actions in different process domains. For example, evidence of human dominance is more widespread in fluvial and coastal records than in aeolian and cryospheric records, so geomorphologically the Anthropocene would inevitably comprise a highly diachronous lower boundary. Even to identify this lower boundary, research would need to focus on the disambiguation of human effects on geomorphological and sedimentological signatures. This would require robust data, derived from a combination of modelling and new empirical work rather than an arbitrary ‘war of possible boundaries’ associated with convenient, but disputed, `golden spikes’. Rather than being drawn into stratigraphical debates, the primary concern of geomorphology should be with the investigation of processes and landform development, so providing the underpinning science for the study of this time of critical geological transition

Holocene-scale fire dynamics of central European temperate sprucebeech forests

This study investigated the long-term role and drivers of fire in the central European temperate sprucebeech forests from Prášilské Jezero, Czech Republic. The results illustrate the complex relationship between broad-scale climate, vegetation composition, and local human activities on fire throughout the Holocene. Biomass burning was the highest (average 3 fires/1000 years) and most severe during the early Holocene when fire resistant taxa (Pinus, Corylus and Betula) dominated. Using a Generalized Additive Model to assess the response of dominant canopy taxa to changes in biomass burning and fire severity, response curves demonstrate a positive relationship (p < 0.01) between fire resistant taxa and increases in biomass burning. Norway spruce (Picea abies) established ~10,000 cal yr BP and expanded during peak biomass burning. Response curves show a slight negative relationship with Picea and increasing biomass burning, and a positive relationship with increasing fire severity. This suggests that central European spruce forests may not be significantly impacted by fire. Regional biomass burning dramatically decreased with the expansion of fire sensitive taxa (e.g. Fagus sylvatica) ~6500 cal yr BP, yet no dramatic reduction in local fire frequency occurred. This suggests either human activities or rare fire-promoting climatic events were important in shaping local fire regimes. Fire activity peaked (6 fires/1000 years) ~2500 cal yr BP and paralleled increases in anthropogenic pollen indicators. Fagus response curves illustrates a negative (p < 0.01) relationship with increasing biomass burning and fire severity suggesting that natural Fagus forests may be increasingly vulnerable to projected increases in wildfire occurrence

Timing and pace of ice-sheet withdrawal across the marine-terrestrial transition west of Ireland during the last glaciation

Understanding the pace and drivers of marine-based ice-sheet retreat relies upon the integration of numerical ice-sheet models with observations from contemporary polar ice sheets and well-constrained palaeo-glaciological reconstructions. This paper provides a reconstruction of the retreat of the last British–Irish Ice Sheet (BIIS) from the Atlantic shelf west of Ireland during and following the Last Glacial Maximum (LGM). It uses marine-geophysical data and sediment cores dated by radiocarbon, combined with terrestrial cosmogenic nuclide and optically stimulated luminescence dating of onshore ice-marginal landforms, to reconstruct the timing and rate of ice-sheet retreat from the continental shelf and across the adjoining coastline of Ireland, thus including the switch from a marine- to a terrestrially-based ice-sheet margin. Seafloor bathymetric data in the form of moraines and grounding-zone wedges on the continental shelf record an extensive ice sheet west of Ireland during the LGM which advanced to the outer shelf. This interpretation is supported by the presence of dated subglacial tills and overridden glacimarine sediments from across the Porcupine Bank, a westwards extension of the Irish continental shelf. The ice sheet was grounded on the outer shelf at ~26.8 ka cal bp with initial retreat underway by 25.9 ka cal bp. Retreat was not a continuous process but was punctuated by marginal oscillations until ~24.3 ka cal bp. The ice sheet thereafter retreated to the mid-shelf where it formed a large grounding-zone complex at ~23.7 ka cal bp. This retreat occurred in a glacimarine environment. The Aran Islands on the inner continental shelf were ice-free by ~19.5 ka bp and the ice sheet had become largely terrestrially based by 17.3 ka bp. This suggests that the Aran Islands acted to stabilize and slow overall ice-sheet retreat once the BIIS margin had reached the inner shelf. Our results constrain the timing of initial retreat of the BIIS from the outer shelf west of Ireland to the period of minimum global eustatic sea level. Initial retreat was driven, at least in part, by glacio-isostatically induced, high relative sea level. Net rates of ice-sheet retreat across the shelf were slow (62–19 m a−1) and reduced (8 m a−1) as the ice sheet vacated the inner shelf and moved onshore. A picture therefore emerges of an extensive BIIS on the Atlantic shelf west of Ireland, in which early, oscillatory retreat was followed by slow episodic retreat which decelerated further as the ice margin became terrestrially based. More broadly, this demonstrates the importance of localized controls, in particular bed topography, on modulating the retreat of marine-based sectors of ice sheets

Meta-analysis of northeast Atlantic marine taxa shows contrasting phylogeographic patterns following post-LGM expansions

Background. Comparative phylogeography enables the study of historical and evolutionary processes that have contributed to shaping patterns of contemporary genetic diversity across co-distributed species. In this study, we explored genetic structure and historical demography in a range of coastal marine species across the northeast Atlantic to assess whether there are commonalities in phylogeographic patterns across taxa and to evaluate whether the timings of population expansions were linked to the Last Glacial Maximum (LGM). Methods. A literature search was conducted using Web of Science. Search terms were chosen to maximise the inclusion of articles reporting on population structure and phylogeography from the northeast Atlantic; titles and abstracts were screened to identify suitable articles within the scope of this study. Given the proven utility of mtDNA in comparative phylogeography and the availability of these data in the public domain, a meta-analysis was conducted using published mtDNA gene sequences. A standardised methodology was implemented to ensure that the genealogy and demographic history of all mtDNA datasets were reanalysed in a consistent and directly comparable manner. Results. Mitochondrial DNA datasets were built for 21 species. The meta-analysis revealed significant population differentiation in 16 species and four main types of haplotype network were found, with haplotypes in some species unique to specific geographical locations. A signal of rapid expansion was detected in 16 species, whereas five species showed evidence of a stable population size. Corrected mutation rates indicated that the majority of expansions were estimated to have occurred after the earliest estimate for the LGM (similar to 26.5 Kyr), while few expansions were estimated to have pre-dated the LGM. Conclusion. This study suggests that post-LGM expansion appeared to be common in a range of marine taxa, supporting the concept of rapid expansions after the LGM as the ice sheets started to retreat. However, despite the commonality of expansion patterns in many of these taxa, phylogeographic patterns appear to differ in the species included in this study. This suggests that species-specific evolutionary processes, as well as historical events, have likely influenced the distribution of genetic diversity of marine taxa in the northeast Atlantic