Using the voids to fill the gaps: caves, time, and stratigraphy

Abstract

Abstract Karstification produces a unique and spatially complex architecture of accommodation space for the accumulation of later sediments. The sedimentary record within caves can act as a repository for stratigraphic and palaeoenvironmental information that has been locally removed by subsequent surface erosion. Caves and karst also allow for the preservation of biota not usually found in the fossil record. Pennsylvanian palaeokarst from Illinois, USA, illustrate the potential of ancient caves as a home for ‘lost stratigraphy’. These palaeocaves have dissolutional features associated with contemporaneous sediment influx (paragenesis), indicating that speleogenesis and cave sediment deposition were synchronous. These features also provide evidence of changing water tables. The fill within the caves suggests multiple flood events on the surface. The enclosed biota contains rare upland plants, such as conifers, as well as scorpions. Both plants and animals preserve original organic constituents. The presence of charcoal, as well as diagnostic polyaromatic hydrocarbons, point to wildfires and thus dry episodes on the land surface. The cave fills are outliers from correlative formations in the region. The filled voids of these ancient caves thus fill palaeontological, palaeoenvironmental, and stratigraphic gaps.