Constructing vertical measurement logs using UAV-based photogrammetry: Applications for multiscale high-resolution analysis of coarse-grained volcaniclastic stratigraphy

Abstract

Volcaniclastic stratigraphy can be difficult to map and describe due to its complex nature. However, such stratigraphy preserves information about fluctuations in volcanic activity and sedimentation and is vital to understanding volcanic systems. Uncrewed aerial vehicle (UAV) based analysis of volcanic stratigraphy can enhance mapping and analysis, especially on vertical surfaces where outcrop exposure is greatest. Here we present a method for using small UAVs to produce vertical grain size and bedding measurement logs, or quantitative stratigraphic columns, of vertical volcaniclastic stratigraphy. We demonstrate the range of high-accuracy measurements and parameters that can be collected for building measurement logs using consumer grade UAVs through a case study in the Marysvale volcanic field where we collected 34,422 grain measurements from 21 individual units. The purpose of producing such measurement logs is to enhance lithofacies analysis through the use of large quantitative datasets and improve the reproducibility of data reporting. Whereas descriptions of volcaniclastic units such as those describing grading are often reported qualitatively, we describe methods for calculating numerical parameters for enhanced lithologic analysis including grain size, grading, clast to matrix ratios, and shape characteristics. The methods described in this paper can enhance field data acquisition, mapping, and quantitative analysis of volcaniclastic deposits and are applicable to a wide range of other geologic settings where coarse-grained clastic sedimentary deposits exist.