Integrating chemostratigraphy and sedimentology for sequence stratigraphy in an enigmatic Middle to Late Devonian mudstone

Sequence stratigraphy in fine-grained successions is often challenging with traditional datasets, and in such intervals, chemostratigraphy is increasingly used to facilitate interpretations. In this study, we present an example from mudstone units of the Horn River Group (Northwest Territories, Canada), which provide a local record of Middle to Late Devonian marine conditions. The dataset comprises geochemical composition data from X-ray fluorescence (XRF), mineralogical data from X-ray diffraction (XRD), wireline logs, total organic carbon (TOC) profiles, and lithological core and thin section descriptions. We first focus on a mudstone core with high-resolution thin-section and geochemical results, enabling the evaluation of chemostratigraphic signatures associated with surfaces and systems tracts in the Horn River Group. By employing chemostratigraphic proxies for terrigenous sediment supply and proportion of biogenic silica, sequence stratigraphic analysis is extended to three cores and five outcrops lacking extensive thin section coverage. Six complete transgressive–regressive (T–R) sequences are identified and correlated in the Horn River Group, comprising higher-resolution cycles in relative sea-level and sediment supply, which are superimposed on previously identified larger-scale sequences. The sequence stratigraphic framework presented illustrates the local balance between relative sea-level rise and sediment supply along the northwestern margin of Laurentia during the Eifelian to the Frasnian. Moreover, this study demonstrates the utility of integrating chemostratigraphic proxies with sedimentological results as a means of sequence stratigraphic interpretation and correlation in mudstone intervals.