There is no such thing as ‘undisturbed’ soil and sediment sampling: sampler-induced deformation of salt marsh sediments revealed by 3D X-ray computed tomography

Carr, Simon; Diggens, Lucy M.; Spencer, Kate L.

doi:10.1007/s11368-020-02655-7

Cited by 10 publications

(5 citation statements)

References 69 publications

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“…Core NT05 (2.47‐m) was chosen from possible high marsh cores for establishing a detailed chronology given its central location and particularly clear earthquake stratigraphy (Figure 2b). NT05 had a total of 10.5 cm (4%) of compaction (based on the difference in the distances to the surface inside and outside the PVC liner), similar to what others have observed (Carr et al., 2020). Within NT05, we focused on the upper 77 cm, which extended from just below the likely 1700 CE earthquake/tsunami deposit to the modern high marsh.…”

Section: Methodssupporting

confidence: 86%

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Recovery Rate of a Salt Marsh From the 1700 CE Cascadia Subduction Zone Earthquake, Netarts Bay, Oregon

Peck

Guilderson

Walczak

et al. 2022

Geophysical Research Letters

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Since the 1700 CE Cascadia Subduction Zone earthquake and associated coseismic subsidence and tsunami, vegetated intertidal habitats have reestablished across Pacific Northwest estuaries, yet timescales and mechanisms of recovery are uncertain. We investigated the timescale of salt marsh reestablishment in Netarts Bay, Oregon following the 1700 CE earthquake using a combination of excess 210Pb, 14C, stratigraphic constraints, and Bayesian age‐depth modeling. Coseismic subsidence lowered the area to low/mid marsh, which persisted for 200 years before transition to modern high marsh. The modern high marsh now appears in dynamic equilibrium with modern sea level rise. In addition to serving as a methodological proof of concept for dating the past 300 years, these results provide insight into intertidal morphodynamic response to large perturbations along tectonically active margins.

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Section: Methodssupporting

confidence: 86%

“…Disturbance to the sediment profile, particularly compaction, is common in stratigraphic studies using cores (Carr et al., 2020). Comparison between measured and modeled ρ DB , based on the downcore OM (Figure S5 in Supporting Information ; Bird et al., 2004), indicates that the 10.5 cm of compaction is relatively uniform over the top 70 cm.…”

Section: Resultsmentioning

confidence: 99%

Recovery Rate of a Salt Marsh From the 1700 CE Cascadia Subduction Zone Earthquake, Netarts Bay, Oregon

Peck

Guilderson

Walczak

et al. 2022

Geophysical Research Letters

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“…The replicates were spaced within 0.5-2 m from one another to ensure that all replicates are independent but have similar substrates. The sediment cores were collected to minimize disturbance of structural features, as summarized in Carr et al (2020). After extraction, the cores were stored upright in a cooling box filled with bubble wrap to minimize disturbance during transport, and stored at 4 C until required.…”

Section: Methodsmentioning

confidence: 99%

Effect of vegetation cover and sediment type on 3D subsurface structure and shear strength in saltmarshes

Chirol

Spencer

Carr

et al. 2021

Earth Surf Processes Landf

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The vulnerability of saltmarshes to lateral erosion at their margin depends on the local biogeomorphological properties of the substrate. In particular, the 3D architecture of pore and root systems is expected to influence shear strength, with repercussions for the wider-scale stability of saltmarshes. We apply X-ray computed microtomography (μCT) to visualize and quantify subsurface structures in two UK saltmarshes at Tillingham Farm, Essex (silt/clay rich substrate) and Warton Sands (sand-rich substrate), with four types of ground cover: bare ground, Spartina spp, Salicornia spp and Puccinellia spp. We extracted μCT structural parameters that characterize pore and root morphologies at each station, and compared them with field measurements of shear strength using a principal component analysis and correlation tests. The 3D volumes show that species-dependent variations in root structures, plant colonization events and bioturbation activity control the morphology of macropores, while sediment cohesivity determines the structural stability and persistence of these pore structures over time, even after the vegetation has died. Areas of high porosity and high mean pore thickness were correlated to lower values of shear strength, especially at Tillingham Farm, where wellconnected vertical systems of macropores were associated with current or previous colonization by Spartina spp. However, while well-connected systems of macropores may lower the local deformation threshold of the sediment, they also encourage drainage, promote vegetation growth and reduce the marsh vulnerability to hydrodynamic forces. The highest values of shear strength at both sites were found under Puccinellia spp, and were associated with a high density of mesh-like root structures that bind the sediment and resist deformation. Future studies of marsh stability should ideally consider time series of vegetation cover, especially in silt/clay-dominated saltmarshes, in order to consider the potential effect of preserved buried networks of macropores on water circulation, marsh functioning and cliff-face erosion.

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“…In order to obtain in situ intact samples it is essential that 'undisturbed' samples are acquired -a process fraught with many problems some almost impossible to overcome with any degree of assurance (cf. Carr et al, 2020). Typically, field samples are taken using Kubiëna or mammoth tins gently inserted into an exposed face (Fig.…”

Section: Sampling and Impregnation Methodsmentioning

confidence: 99%

Glacial microsedimentology—a new lens to investigate glacial sediments—a review

Menzies

2023

Can. J. Earth Sci.

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Glacial sediment research using thin sections began post-1945. Microsedimentology examines sediments at the microscopic level deriving insights into the processes of glacial erosion, transport, and deposition. Two issues exist (1) the difficulty by some in recognizing microstructures in thin section; and (2) the absence of quantitative data making data reproduction difficult. The latter is hard to resolve but more image capture and software methodologies are now becoming available at reasonable costs. Thin sections are two-dimensional sections of three-dimensional objects, and this must be considered when measurements, fabrics and other data are assessed. Research into the micro-aspects of glacial sediments followed a typical scientific trajectory: thin sections description with little uniformity or common ‘language’ for observed microstructures: standardization allowed comparison between different sediments; with standardization, came an open-ended classification; and with cross-comparison with multiple thin sections - a quantitative means of study needs developed. It has become apparent that the basic principles of structural geology had to be applied. Thus, micromorphology has subsumed into a microsedimentological study of glacial sediments where stress parameters, structural fabrics and the mapping of deformation structures and contextual integration allows an understanding of how these sediments have been formed. Examples of the development stages of glacial micromorphology / sedimentology are presented here as well as discussion of future avenues of study. In addition, multiple thin sections are used to illustrate the many aspects of glacial micromorphology and the parameters necessary to understand glacial sedimentology and the processes of glacial sedimentation.

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There is no such thing as ‘undisturbed’ soil and sediment sampling: sampler-induced deformation of salt marsh sediments revealed by 3D X-ray computed tomography

Cited by 10 publications

References 69 publications

Recovery Rate of a Salt Marsh From the 1700 CE Cascadia Subduction Zone Earthquake, Netarts Bay, Oregon

Recovery Rate of a Salt Marsh From the 1700 CE Cascadia Subduction Zone Earthquake, Netarts Bay, Oregon

Effect of vegetation cover and sediment type on 3D subsurface structure and shear strength in saltmarshes

Glacial microsedimentology—a new lens to investigate glacial sediments—a review

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