Abstract In 1888, inspired by fieldwork in what has become known as the Moine Thrust Belt, NW Scotland, Henry Cadell conducted a pioneering series of analogue deformation experiments to investigate the structural evolution of fold–thrust belts. Some experiments showed that imbricate thrusts build up thrust wedges of variable form, without requiring precursor folding. Others demonstrated a variety of fold–thrust structures and how heterogeneities in basement can localize thrust structures. These experiments are described here and used to draw lessons on how analogue deformation experiments are used to inform the interpretation of fold–thrust structures. Early adopters used Cadell's results as guides to structural styles when constructing cross-sections in thrust belts. His models and the host of others created since serve to illustrate part of the range of structural geometries in thrust belts. However, as with much subsequent work, Cadell's use of a deformation apparatus, with a fixed basal slip surface, biases perceptions of fold–thrust belts to be necessarily ‘thin-skinned’ (experimental design bias) and can simply reinforce established interpretations of natural systems (confirmation bias). So analogue deformation experiments may be unreliable guides to the deterministic interpretations of specific fold–thrust structures in the sub surface of the real world.

Abstract This research aims to quantify the geophysical signature of the laminated layer, one of the main layers constituting the weathering profile of hard rocks. This laminated layer acts as a marker for locating the underlying groundwater productive stratiform fractured layer (SFL). The study is based at two sites on the interpretation of 50 km of electrical resistivity tomography (ERT) profiles, compared with outcrops and boreholes by geophysical modelling. For the first time, the geophysical signature of the laminated layer, located at the base of the saprolite, is characterized within granite formations. Where the stratiform weathered layer is detected by pole-dipole ERT profiles, the laminated layer is identified as a resistant layer on 90% of the SFL length using an appropriate inversion method. In addition, this layer is also revealed for the first time in certain types of metamorphic formations; here it is revealed in micaschists (62% of the SFL length). The location of the laminated layer in the weathering profile is important (1) for water well siting by determining if an underlying SFL exists in the weathering profile and (2) for assessing the residual thickness of the saprolite, and then evaluating water storage and the protection of the SFL aquifer. Supplementary material: A table presenting the ERT profiles used in this study, with the type of array and inversion method, the inversion parameters (RMSE and number of iterations), and the length of the inverted profiles where the laminated layer (LL) and the stratiform fractured layer (SFL) are identified is available https://doi.org/10.6084/m9.figshare.c.4088768

Abstract A phenomenon unique to fine-grained sediment is its ability to alter the physical characteristics of the overlying water column. Although the present state of research recognizes many aspects of fine-grained seabed and water column interactions, this study documents how an energetic sandy, shallow marine system can autogenically transition to a system capable of accumulating fine-grained bedforms to clinoforms. To understand these transitional processes this study examines the lithostratigraphy and depositional history of the Suriname portion of the Guiana Coast (French Guiana, Suriname, and Guyana). Four major lithologic facies (Pre-Holocene silty clay; peat-rich silty clay; sandy mud; silty clay with cheniers) were derived from the Late Holocene sea level rise and influx of sediments emitted from the Amazon River. Since approximately 6000 BP, ~10 to 20% of Amazon-derived sediments bypass the Amazon shelf and are transported northwestward toward the study area. Along the Suriname coast (~900 km from the Amazon), however, significant mud accumulation did not commence until 3000 to 3500 BP. Suspended sediments can travel this distance in less than 1 month. A migrating (1.5 km/yr) mud bank could travel the 900 km from the Amazon mouth in 600 years or, after formation of a 400-km-wide subaqueous Amazon delta (by 1200 BP), migrate the remaining 500 km by 4500 BP, still 1000 to 1500 years prior to the time period during which radiocarbon dates indicate significant mud accumulation began. Consequently, either there was a major hiatus in sediment transport and accumulation between 6000 BP to 3000 BP or some other transport process other than suspension or mud-bank migration-controlled initial mud accumulation. Assuming steady-state conditions, lateral accretion rates from 6000 BP to 3000 BP equate to 0.3 to 0.4 km/yr. These rates, which are similar to migration rates cited by previous studies for the trailing edges of mud banks in French Guiana, may reflect postmigration erosion of the initial mud banks. Whether there is an erosional overprint or some other process, this lateral accretion rate is an indicator of the amount of fluid mud necessary for ‘mud to beget mud.’ More general prerequisites necessary for a shallow marine setting to autogenically form fine-grained clinoform-scale accumulations are, first, a single large source of muddy sediments (a major river) and, secondly, unidirectional transport processes to concentrate and continuously supply mud sediments to the system.