Abstract. It is generally accepted that geological line work, such as mapped boundaries, are uncertain for various reasons. It is difficult to quantify this uncertainty directly, because the investigation of error in a boundary at a single location may be costly and time consuming, and many such observations are needed to estimate an uncertainty model with confidence. However, it is recognized across many disciplines that experts generally have a tacit model of the uncertainty of information that they produce (interpretations, diagnoses, etc.) and formal methods exist to extract this model in usable form by elicitation. In this paper we report a trial in which uncertainty models for geological boundaries mapped by geologists of the British Geological Survey (BGS) in six geological scenarios were elicited from a group of five experienced BGS geologists. In five cases a consensus distribution was obtained, which reflected both the initial individually elicited distribution and a structured process of group discussion in which individuals revised their opinions. In a sixth case a consensus was not reached. This concerned a boundary between superficial deposits where the geometry of the contact is hard to visualize. The trial showed that the geologists' tacit model of uncertainty in mapped boundaries reflects factors in addition to the cartographic error usually treated by buffering line work or in written guidance on its application. It suggests that further application of elicitation, to scenarios at an appropriate level of generalization, could be useful to provide working error models for the application and interpretation of line work.

Abstract:Modeling landscape evolution requires quantitative estimates of erosional processes. Dating 12 erosional landscape features such as escarpments is usually difficult because of the lack of datable deposits. 13Some escarpments and valley margins are associated with the formation of mass-movement caves, sometimes 14 known as 'gull' or 'crevice' caves, which are typically restricted to within 0.5 km of the valley margin or scarp 24Quantifying rates of landscape processes is an essential requirement for constructing, validating and 25 constraining increasingly sophisticated landscape evolution models (Pazzaglia, 2003; Tucker and 26 Hancock, 2010). With quantitative data, rates of landform development can be evaluated, enabling 27 the relative importance of geomorphological processes to be established and facilitating the 28 development of more realistic landscape evolution models. Moreover, quantification is extremely 29 important in predictive work, as it is required for estimating the impact of future global climate 30 change. Whilst some geomorphological processes can be easily quantified, such as the rate of valley 31 incision by dating river terrace sequences (Maddy, 1997; Maddy et al., 32 2000;Maddy et al., 2001), dating cave levels in carbonate terrains (Farrant et al., 1995; Palmer, 33 2007), or by dating other alluvial materials such as tufa (Banks et al., 2012), deducing the timing and 34 rates of other processes such as valley widening and escarpment ( or 'scarp') retreat is harder to 35 determine. However, both rates of valley incision and scarp retreat are required to understand how 36 valleys evolve. Do they develop by progressive incision and valley widening through fluvial channel 37 migration and concurrent hill slope retreat or is the gross relief generated 'in-situ' by the progressive 38 removal of the more erodible lithologies over multiple glacial-interglacial cycles? In the latter 39 scenario, valley width is influenced more by lithological heterogeneity and variable susceptibility to 40 periglacial weathering (Murton and Belshaw, 2011) fissures may contain speleothem deposits which can be precisely dated using uranium series 53 methods (Lenart and Pánek, 2013). As the gull-caves can only develop after a scarp has formed, the 54 basal age of the oldest speleothems within them provide a minimum age for cave inception and 55 hence scarp formation. Moreover, as the gull-caves only form close to the scarp edge, they can be 56 used to determine a chronology of scarp retreat. Taken together with rates of valley incision 57 determined from fluvial terraces, the spatial and temporal pattern of valley development and scarp 58 formation can be resolved and models of regional landscape evolution erected. 59The study area 60In this paper, we use the lower Severn valley and the Cotswold Hills in southern England (Figure 1) Triassic and Lower Jurassic (Lias Group) mudstones ( Figure 1) that occupy the core of this basin. The 77 eastern side is marked by the prominent escarpment of the Cotswol...

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Bathonian to Oxfordian strata occur onshore in two principal locations over 30 km apart on the coast of the Moray Firth, at Brora and Balintore. The existing lithostratigraphy has the same formation names applied to both successions despite profound differences, exemplified in their schemes of local members. Furthermore, three of the formation names include the same place name, and use obsolete lithological terms.We consider that all the Bathonian to Oxfordian members are satisfactory, and propose their retention with original names, with one exception, to provide continuity with the superseded formational scheme. We propose retention of the Brora Coal Formation as currently defined.The Brora Argillaceous, Brora Arenaceous and Balintore formations at Brora are unsatisfactory in a modern context and we propose: i) a new Strathsteven Mudstone Formation, which is mudstone-dominated, and generally coarsens-upwards.ii) a Clynekirkton Sandstone Formation, which is sandstone-dominated and generally coarsens upwards.This formation scheme employs unique geographical names and modern and appropriate lithological terminology. Furthermore, the boundary between the Strathsteven and Clynekirkton formations is placed at a junction that is a change from mud-and silt-dominated lithologies to silt-and fine-and medium-grained sand and is mappable.We consider that the Callovian-Oxfordian succession at Balintore should be assigned to a single formation, viz. the revised Balintore Formation. Apart from the basal Brora Roof Bed, the succession at Balintore does not lithologically resemble that at Brora, and the scheme of the Brora Argillaceous Formation, Brora Arenaceous Formation, and the Balintore Formation as previously defined is unworkable here.2