Interplay of Holocene surface faulting and climate in the Central Po Plain, Italy

Understanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.

Cortinarius ochrolamellatus (Agaricales, Basidiomycota): a new species in C. sect. Laeti, with comments on the origin of its European-Hyrcanian distribution

Geographic distributions of mushroom-forming fungi usually remain elusive because of the scarcity of occurrence data. However, the increasing number of environmental and ectomycorrhizal (EcM) root tip DNA sequences deposited in public repositories provides a unique opportunity to expand our knowledge about fungal geographic distributions, even at the intercontinental scale. Here, we present Cortinarius ochrolamellatus, a new EcM species likely associated to a number of oak species (Quercus spp.) in the Iberian Peninsula, Sardinia, Central Italy, France, and Norway. The morphological and phylogenetic study of the collections allowed us to include it within C. section Laeti. Furthermore, the combination of specimen-based and EcM root tip ITS data in the phylogenetic analysis revealed the presence of this species in the Hyrcanian Quercus forests of northern Iran. Hence, the present study adds further evidence for a biogeographic link between Europe and these Asian mountainous forests concerning fungi. The inferred Pleistocene temporal framework for the origin and diversification events in C. ochrolamellatus suggests that the distribution of this EcM species was likely driven by the distribution of its Quercus tree hosts during the complex Eurasian Quaternary history.

A landsystems approach to understanding the evolution of ice-cored topography and distribution of retrogressive thaw slumps, western Canadian Arctic

<p>The landscape of the Tuktoyaktuk Coastlands, western Canadian Arctic is dominated by glacial and geocryological processes that have modified, imprinted and sculpted the surface, depositing surficial materials upon underlying bedrock. Climate warming continues in this region at a rate that is twice the global average, and retrogressive thaw slump (RTS) activity is increasing. Recently, RTS distribution was associated with glacial limits reached by the Laurentide Ice Sheet and corresponding morainal deposits, but RTS are common in other local terrain units. In this glacial-marginal region, permafrost existed pre-glacially, and non-glacial geomorphic processes occurred throughout the Late Quaternary. Superimposed on these conditions are the effects of thermokarst during the Holocene climatic optimum, followed by a period of cooling. Collectively, these processes and associated forms and deposits have contributed variously to preservation, development, or degradation of permafrost and ground ice. The multifaceted Late Quaternary history in this region has impeded understanding of the distributions of ice-cored topography and RTS. For example, rather than glaciogenic ice, the long reigning regional model for ice-cored topography is according to post-glacial development of intrasedimental segregation-intrusion ice. Toward better understanding the evolution of the whole landscape and the distribution of climate-sensitive terrain, we use a landsystems approach as a means to understand how the ice-cored topography developed where RTS form, through analysing the cryostratigraphy. To this end, we identify 6 RTS representing a suite of ice-cored topographic settings, including: (i) preserved basal glacial ice facies within clayey diamict that has been thrusted and folded by glacial push representing morainal deposits of the Sitidgi Stade; (ii) ice contact outwash sediments associated with the Sitidgi Stade, overlying a thermo-erosional contact with underlying basal glacial icy diamict of the Toker Point Stade; (iii) deformed basal glacial ice, eroded down by meltwater-deposited outwash sands some time between the Toker Point and Sitidgi Stades (could be ca. 12.9 kyr BP); (iv) massive, undeformed segregation-intrusion basal ice, likely formed subglacially by freezing of intrasedimental water in pre-existing Pleistocene sands into the base of the glacier, overlain by glacial diamicton;  (v) deformed basal ice facies of intermediate Toker Point – Sitidgi Stades, with an upper layer that may be supra-glacial melt-out till into which segregated ice formed; and (vi) segregation ice that formed as permafrost aggraded into glaciolacustrine clays deposited in proglacial or glacially dammed basins, that was subsequently eroded down by glaciofluvial outwash (Sitidgi Stade). To summarize, the distribution of RTS reflects primarily the distribution of icy basal glacial diamict preserved in moraines, but also basal ice and icy basal diamict that are preserved beneath glaciofluvial deposits, segregation ice in glaciolacustrine deposits, and massive segregation-intrusion ice in Pleistocene sands beneath a till plain.</p>

Chapter 7 Quick clay behaviour in sensitive Quaternary marine clays – a UK perspective

The term quick clay has been used to denote the behaviour of highly sensitive Quaternary marine clays that, due to post depositional processes, have the tendency to change from a relatively stiff condition to a liquid mass when disturbed. On failure these marine clays can rapidly mobilise into high velocity flow slides and spreads often completely liquefying in the process. For a clay to be defined as potentially behaving as a quick clay in terms of its geotechnical parameters it must have a sensitivity (the ratio of undisturbed to remoulded shear strength) of greater than 30 together with a remoulded shear strength of less than 0.5 kPa. The presence of quick clays in the UK is unclear, but the Quaternary history of the British islands suggests that the precursor conditions for their formation could be present and should be considered when undertaking construction in the coastal zone.

The bones beneath the streets: drifting through London’s Quaternary

This article reflects on a Situationist dérive in Central London, which mobilised a creative engagement with the city’s Quaternary history (the last 2.6 million years). The aim was to animate paleoecological knowledge in the resistant, opaque and frenetic environment of a dense urban centre. This brief excursion into an alternative London is offered as a model for contemporary drifting that stretches out beyond our immediate situation to connect to successive geological and biological strata, reframing experiences of the urban environment through shifting scales and chronologies. The Situationists had declared ‘sous les pavés, la plage!’ (under the paving stones, there is a beach!), evoking the playful space of possibility behind the veneer of the city’s systems and structures. This drift aimed to search even deeper, encountering spectral inhabitations revealed by the bones beneath the streets. The article argues that uncovering these hidden ecologies has the potential to counter the urban prevalence of spectacular representations of wildlife and develop an eco-politics of co-existence.