Sediment textural characterisation of the Ravenglass Estuary: development of a method to predict palaeo sub-environments from estuary core samples

Simon, Naboth, Worden, Richard H ORCID: 0000-0002-4686-9428, Muhammed, Dahiru ORCID: 0000-0001-5025-5456, Utley, James EP ORCID: 0000-0003-0397-5607, Verhagen, Iris ORCID: 0000-0003-1090-687X, Griffiths, Joshua and Wooldridge, Luke (2021) Sediment textural characterisation of the Ravenglass Estuary: development of a method to predict palaeo sub-environments from estuary core samples. Sedimentary Geology, 418. p. 105906.

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Abstract

Here we present a new way to automatically classify the exact sub-environment of deposition of sediment from estuarine sediment cores. It can be challenging to define the exact sub-environment of deposition in core as sediment of a given appearance, or facies, can be found in multiple settings. This issue is important given that petrophysical, geomechanical and reservoir quality properties of sedimentary rocks are typically strongly influenced by the specific sub-environment of deposition. Here, using a ten-fold classification of depositional subenvironments, we have determined the sub-environments of 482 sample sites from the Ravenglass Estuary, in NW England, UK. We then analysed the textural characteristics of each of these samples using laser particle size analysis. A novel automatic textural classification scheme was then developed using a combination of visual discrimination of gravel and vegetated surfaces, principal component analysis and a recursive partitioning routine (RPART) in Rstudio. The new automatic textural classification scheme can resolve eight of the ten subenvironments of deposition: gravel beds, salt-marsh, mud flat, mixed flat, sand flat, tidal inlet, combined south foreshore/ebb-tidal delta and combined tidal inlet/north foreshore. Our scheme cannot differentiate the spatially adjacent tidal inlet and north foreshore sediments as they are texturally identical. Similarly, the scheme cannot differentiate the spatially adjacent ebb-tidal delta and southern foreshore sediments as they also are texturally identical. We have applied our surface-calibrated method to a 3 m Holocene core drilled through fine-grained surface sand flats into interbedded fine- and coarse-grained sands in the Ravenglass Estuary and successfully defined palaeo sub-environments of deposition. Our automatic approach to the definition of palaeo-environment of deposition approach supersedes a simple lithofacies-based approach for the Ravenglass Holocene core as we can define, cm-by-cm, how the exact estuarine sub-environments evolved over the last 10,000 years. This approach could also be applied to other modern estuaries and could be trialled for use with ancient and deeply buried sedimentary rocks deposited in equivalent marginal marine estuarine environment.

Item Type:	Article
Uncontrolled Keywords:	Estuary, Estuarine sediment, Grain size, Sorting, Kurtosis, Sediment classification, Environmental interpretation, Holocene, Sub-depositional environment, Recursive partitioning, Classification diagram
Divisions:	Faculty of Science and Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	19 Apr 2021 08:38
Last Modified:	04 May 2023 08:57
DOI:	10.1016/j.sedgeo.2021.105906
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3119537