Documenting archaeological thin sections in high‐resolution: A comparison of methods and discussion of applications

Abstract

Optical thin section observations represent the core empirical basis for most micromorphological interpretations at archaeological sites. These observations, which often vary in size and shape, are usually documented through digital graphic representations such as photomicrographs, scans, or figures. Due to variability in documentation practices, however, visual thin section data can be captured with a range of methods and in many different formats and resolutions. In this paper, we compare and evaluate five common image‐based methods for documenting thin sections in high‐resolution: a flatbed scanner, a film scanner, a macro photography rig, and conventional stereo and light microscopes. Through the comparison results, we demonstrate that advances in digital imaging technology now allow for fast and high‐resolution visual recording of entire thin sections up to at least ×30 magnification. We suggest that adopting a digital micromorphological documentation practice has several advantages. First, a digital thin section may be observed more efficiently and consistently, for example, on a computer screen, and the spatial configuration of large or complex features may be more accurately documented. Second, they allow for the establishment of digital repositories that may promote scientific reproducibility and inter‐laboratory communication, as well as lay the foundations for more consensus‐based educational training of archaeological micromorphology.

Hidden in plain sight: A microanalytical study of a Middle Stone Age ochre piece trapped inside a micromorphological block sample

“…It should be noted that during the slicing of the impregnated block sample, some of its original thickness, including the trapped ochre piece, was removed by the saw blade (>10 mm). By applying thin section‐wide documentation procedures described by Haaland et al (2019), and by following general (Courty et al, 1989; Stoops, 2003) and site‐specific descriptive protocols (Haaland, 2018), we characterise the sedimentary composition and microstratigraphic configurations.…”

Site formation processes and urban transformations during Late Antiquity from a high‐resolution geoarchaeological perspective:Baelo Claudia, Spain

“…On the other hand, these authors highlighted the potential of digital recording of information through high‐resolution images, which should not be viewed as a complement to the research, but rather a substantial part of the data (Gutiérrez‐Rodríguez, Toscano, & Goldberg, ). Taking inspiration from previous literature (Carpentier & Vandermeulen, ; Fisher et al, ; Gutiérrez‐Rodríguez et al, ; Haaland, Czechowski, Carpentier, Lejay, & Vandermeulen, ), we explore in this paper new possibilities of data collection, processing and presentation through combining SfM technologies and high‐resolution scans of the studied thin sections. Initially, the site was included in a global reference system (UTM ETRS89‐29N) using a total station.…”

“…Commercial software Agisoft Photoscan was useful for this purpose due to the implementation of Scale‐Invariant Feature Transform (SIFT) and DMVS (Dense Multi View Stereo) algorithms (Lowe, ; Scharstein & Szeliski, ). Finally, the thin sections were scanned using a Nikon Super CoolScan 8000 ED (Nikon, Japan) film scanner, obtaining high‐resolution scans of the thin sections (4,000 dpi), conveniently scaled and georeferenced following the standard procedures developed by the Geoarchaeology Working Group of the University of Tübingen (Haaland et al, ). Polarizing sheet film were intercalated between the film scanner light source and the thin sections, providing PPL and XPL illumination.…”

Geoarchaeological investigation of occupation deposits in Blombos Cave in South Africa indicate changes in site use and settlement dynamics in the southern Cape during MIS 5b-4

“…Encouraged by recent developments in high-resolution geoarchaeological methods (e.g., Goldberg et al, 2012;Miller et al, 2013;Aldeias et al, 2014;Haaland et al, 2017Haaland et al, , 2019, our goal in this paper is to assess whether changes in local site use and occupational intensity occurred at Blombos Cave during Marine Oxygen Isotope Stages (MIS) 5b-4 (ca. 88-72 ka ago).…”