A comparison of micro-CT and thin section analysis of Lateglacial glaciolacustrine varves from Glen Roy, Scotland. (15th April 2015)

• Record Type: Journal Article
• Authors: Bendle, Jacob M.; Palmer, Adrian P.; Carr, Simon J.
• Is Part Of: Quaternary science reviews. Volume 114(2015)
• Page Start: 61
• Page End: 77
• Publication Date: 2015-04-15
• Subjects: X-ray computed microtomography (μCT) -- 3D rendered volumes -- Thin section micromorphology -- Laminated lacustrine sediments -- Varves -- Microfacies -- Quaternary; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2015.02.008
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Despite the prevalence of thin section analysis in studies of Quaternary sediments, there are limitations associated with the production of thin sections (sediment modification) and the inherently 2D view that a thin section affords. Non-destructive and rapid scanning technologies such as X-ray computed microtomography (μCT) enable material samples to be visualised and analysed in 3D. In a Quaternary context, however, such techniques are in their infancy. This paper assesses the optimum approach to μCT analysis of Quaternary sediments, applying the method on Lateglacial glaciolacustrine varves from Glen Roy, Scotland. Scan datasets are examined at each stage of the thin section process and comparisons are made between 2D μCT images and thin sections for the recognition of 2D sediment features, with further appraisal of 3D models to identify 3D sediment structures. Comparable sediment features are observed in 2D μCT images and thin sections, however, the μCT imaging resolution determines the precision of microfacies descriptions. Additional 3D structures are distinguished from volumetric models that are otherwise impossible to identify in thin section slides. These 3D structures can locally alter sediment properties (e.g. layer thickness) as seen in 2D thin sections and/or digital images, although such variation cannot be detected with these media. It has been demonstrated that clear benefits exist in understanding the 3D structure of Quaternary sediments, both prior to thin-sectioning to avoid complicating (e.g. deformation) structures, and after thin-sectioning to establish the complex 3D context of 2D datasets. It is recommended that μCT and thin section techniques are applied in parallel in future studies, which will profit from the integration of 'true' 3D data. It is also advised that samples are scanned soon after field sampling, due to the significant modification of in situ sediment structures that can occur during thin section processing. Highlights: Novel application of μCT scanning for 3D imaging of lacustrine varves. Identification of 3D sediment features that are unobservable in thin sections. 3D structures influence the 2D properties of sediment features as observed in thin section. Modification of in situ sediment structures due to thin section processing. Quaternary (micro-)sedimentological studies will benefit from the integration of 3D μCT and 2D thin section techniques.