Devonian palaeoenvironmental dynamics in Colombia: An integrated sedimentological and geochemical exploration

Abstract

During the Devonian Period, many marine basins around the world reflected remarkably high global sea levels. In this context, the Devonian depocentres in northwestern South America offer a perspective on basin dynamics due to their distinct sedimentation and relatively low-deposition rates. This multidisciplinary study aims to understand these processes by characterising a well-preserved late Emsian-early Frasnian section in Colombia’s Floresta Massif. We integrated facies analysis, lithogeochemistry, and organic geochemistry to gain insights into the depositional systems shaping the basin's sedimentary architecture. We recognised five facies associations, corresponding to mixed transgressive platform environments with a predominance of siliciclastic and storm influence, gradually evolving into terrestrial environments. The depositional processes and geochemical proxies indicate conditions favourable to the proliferation of planktonic organisms, including water circulation, weathering, adequate salinity, nutrients, temperature, productivity, and low water turbidity. In this scenario, we observed thin, limited intervals exhibiting minimal influence from oxidation-reduction processes, whereas the overall sedimentary environment presents challenges for organic matter preservation, impacting its distribution and quality. The vertical stacking pattern analysis identified small cycles (less than 0.5m thick) and much larger-scale cycles (200–300 m thick) throughout the succession, which show alternations between transgressive and regressive phases. Additionally, the sedimentary input to the basin, while generally stable and not notably low (ca. 0.23 m/Ma), reveals subtle variations in sedimentation rates. These variations are evidenced by cycles with varying thicknesses and sedimentary condensation, aligning with global-sea level curves and previous tectonic models, suggesting the influence of a waning arc with restrained magmatic activity on the Colombian Devonian marine basin. By uncovering the unique sedimentation patterns and depositional environments of this region, we contribute valuable knowledge to the broader study of basin dynamics. While recognising the preliminary nature of the descriptions provided in the present study, our insights shed light on the complex processes shaping sedimentary systems, emphasising the need for further detailed investigations into the timing of Devonian events and cycles.