Compaction

Brain, Matthew J.

doi:10.1002/9781118452547.ch30

Cited by 16 publications

(9 citation statements)

References 28 publications

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“…Sediment compaction may result in post-depositional lowering of sea-level data (Brain, 2015; Brain et al, 2012). While the majority of the Bracky Bridge reconstruction is based on intercalated samples, which are more likely to be influenced by compaction, comparison of basal and intercalated samples suggests this process is unlikely to exert a major influence.…”

Section: Discussionmentioning

confidence: 99%

Holocene relative sea-level changes in northwest Ireland: An empirical test for glacial isostatic adjustment models

2023

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The late-Quaternary relative sea-level (RSL) history of Ireland is complex, positioned at the margins of the former British-Irish Ice Sheet, and subject to the influence of ice unloading and forebulge collapse. Geophysical models of post-glacial isostatic adjustment (GIA) provide estimates of the pattern of RSL change since deglaciation which may be tested and validated with empirical data from proxy records. For the region of northwest Ireland, there is a paucity of high-quality RSL data and, therefore, equivocal evidence to support the GIA models that predict a mid to Late-Holocene RSL highstand of between +0.5 and +2 m above present. This study aims to investigate this model-data discrepancy by reconstructing RSL change from a near continuous salt-marsh sequence at Bracky Bridge, Donegal, spanning the last ca. 2500 years. We develop a transfer function model to reconstruct the vertical position of sea level using a regional diatom training set to quantify the indicative meaning and predict the palaeomarsh elevation of the core samples. A chronology is provided by a combination of 14C and 210Pb data, with sample specific ages derived from an age-depth model using a Bayesian framework. Our reconstruction shows ca. 2 m of relative sea-level rise in the past 2500 years. This is not compatible with some previously published sea-level index points from the region, which we re-interpret as freshwater/terrestrial limiting data. These results do not provide any evidence to support a Mid-Holocene RSL highstand above present sea level. Whilst none of the available GIA models replicate the timing and magnitude of the Late-Holocene RSL rise in our reconstruction, those which incorporate a thick and extensive British-Irish Sea Ice Sheet provide the best fit.

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Section: Discussionmentioning

confidence: 99%

Holocene relative sea-level changes in northwest Ireland: An empirical test for glacial isostatic adjustment models

2023

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“…Soil subsidence is brought about by three basic processes, each of which need to be accounted for (Brain, 2015). These are a) compaction of sediment above the groundwater level due to physical ripening, b) chemical ripening of the sediment above the groundwater level of which mineralization of organic matter (e.g.…”

Section: The Future Of the Pontine Marshesmentioning

confidence: 99%

The Pontine Marshes: An integrated study of the origin, history, and future of a famous coastal wetland in Central Italy

et al. 2023

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The Pontine Marshes (Central Italy) are known for their long drainage history starting early in Roman times and culminating in their reclamation ( bonifica integrale) by the Fascist’s regime under Mussolini, mostly in the 1930s of past century. The geology of this coastal wetland and causes for its drainage problems received limited attention till recently. We reviewed results from recent studies, identified still existing knowledge gaps and performed additional research to fill these, to produce a full description of the Holocene history and drainage of these marshes. Massive coring data that served to map the soils and surficial geology, observations in archaeological excavations, analytical data on soil and sediment characteristics, and radiocarbon datings allowed us to distinguish several phases in this history, with a main break in the early Roman Republican period with the first systematic drainage works. Earlier, natural processes brought about by sea level rise largely controlled its drainage. Once artificial drainage started, soil subsidence became an important process, aggravating the drainage problems. The bonifica introduced mechanical drainage, temporarily masking the impacts of subsidence. We quantified the historical subsidence using DTMs and developed scenarios for the impacts of sea level rise and subsidence in 2100 and 2200, assuming that this rise will be mitigated by a coastal defence system and enhanced capacity of the mechanical drainage. Our results demonstrate the important role of soil subsidence throughout the history of this wetland and need to include subsidence in scenarios for the impacts of sea level rise.

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“…To address the potential for compaction and post-depositional distortion of the Mokomoko Inlet sedimentary sequence, and to 'decompact' the relative sea-level record presented by Garrett et al (2022), we used the geotechnical model of Brain et al (2011Brain et al ( , 2012. 10 Further details of the sampling, preparation, and analysis approach are given by Brain (2015) and Brain et al (2017). In summary, we first determined the geotechnical properties of modern sediments collected from Mokomoko Inlet using nine undisturbed sediment samples, three each from the high, middle, and low marsh (Fig.…”

Section: Geotechnical Analysis and Modellingmentioning

confidence: 99%

“…Sediment compaction lowers foraminifera-bearing sediments from the elevation at which they were originally deposited, potentially resulting in overestimation of the rate of RSL rise (Allen, 5 2000;Brain et al, 2011Brain et al, , 2012. Due to their highly organic nature, the high marsh-sediments favoured for foraminifera-based RSL reconstructions may be more susceptible to compaction than more minerogenic sediments found lower in the tidal frame (Brain, 2015). Regional estimates of rates of sediment compaction can be obtained from sea-level databases (e.g., Horton & Shennan, 2009), but are dependent on the presence of basal peats that rest directly on an incompressible substrate (e.g., Törnqvist et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Resolving Uncertainties in Foraminifera-Based Relative Sea-Level Reconstruction: a Case Study from Southern New Zealand

Garrett

Brain

Hayward³

et al. 2023

Journal of Foraminiferal Research

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Since the pioneering work of David Scott and others in the 1970s and 1980s, foraminifera have been used to develop precise sea-level reconstructions from salt marshes around the world. In New Zealand, reconstructions feature rapid rates of sea-level rise during the early to mid-20th century. Here, we test whether infaunality, taphonomy, and sediment compaction influence these reconstructions. We find that surface (0–1 cm) and subsurface (3–4 cm) foraminiferal assemblages show a high degree of similarity. A landward shift in assemblage zones is consistent with recent sea-level rise and transgression. Changes associated with infaunality and taphonomy do not affect transfer function-based sea-level reconstructions. Applying a geotechnical modelling approach to the core from which sea-level changes were reconstructed, we demonstrate compaction is also negligible, resulting in maximum post-depositional lowering of 2.5 mm. We conclude that salt-marsh foraminifera are indeed highly accurate and precise indicators of past sea levels.

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Compaction

Cited by 16 publications

References 28 publications

Holocene relative sea-level changes in northwest Ireland: An empirical test for glacial isostatic adjustment models

Holocene relative sea-level changes in northwest Ireland: An empirical test for glacial isostatic adjustment models

The Pontine Marshes: An integrated study of the origin, history, and future of a famous coastal wetland in Central Italy

Resolving Uncertainties in Foraminifera-Based Relative Sea-Level Reconstruction: a Case Study from Southern New Zealand

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