A link between a previously unrecognised mass extinction and a period of high rainfall in the Late Triassic – the Carnian Pluvial Episode – was discovered by Mike Simms and Alastair Ruffell in 1987. Triassic caves were seen as key evidence for increased rainfall ~234 Ma ago, but this has been omitted from recent syntheses of the CPE compiled by others. Many Triassic caves contain abundant terrestrial reptiles, including early dinosaurs, but none of these species has ever been found in Triassic surface deposits. The only biostratigraphically useful fossils common to both the caves and surface sediments are Rhaetian (latest Triassic, ~203 Ma) pollen and marine algae found in some sediments at just a few sites. It has since been claimed that all of the Triassic caves are Rhaetian and were formed as marine flank-margin caves during the end-Triassic transgression. This karstic conundrum can readily be resolved through an understanding of karst geomorphology and speleogenesis, without recourse to biostratigraphy.

Mike Simms is a Senior Curator of Geology at National Museums NI (27 years) after a succession of research and teaching post around the UK and at TCD (1989-90). He writes: I have been a caver since the mid-1980s, which informs much of my work on caves. It is not a crowded field, as most geologists are reluctant to venture into tight muddy holes, but there is a degree of naivety among many geologists who think that a cave is just a hole in a rock, which might be why the Triassic caves have been misinterpreted for so long. With the right eyes caves can provide a wealth of information on past landscapes and their evolution.

The extensive gypsum karst of Sivas is one of the most outstanding examples of bare gypsum karst in the world. Its geomorphological landscapes mainly controlled by the geometry of Sivas Thrust which create hanging wall antiformal ridge and a morpho-structural trough with relatively low uplift rate. The Sivas gypsum karst displays several remarkable geomorphic features analysed in this research, including: (1) a well-developed polygonal karst mainly developed in the antiformal ridge; (2) relict valleys; (3) 300 bedrock collapse sinkholes (BCS) mainly in the low-lying area; and (4) 310 cover subsidence sinkholes. (5) unusual gypsum canyons; (6) poljes. The morphology of the BCS, varying from small cylindrical holes to large and deep tronco-conical depressions with gentle slopes reflect to geomorphic evolution of these sinkholes that reach hectometre-scale diameters.

Their evolution, involving substantial enlargement and deepening, is attributed to the solutional removal as solute load of large volumes of gypsum by downward vadose flow. This type of morphological evolution with significant post-collapse solutional denudation differs from that observed in carbonate rocks. Three types of base-level poljes are differentiated based on cartographic relationships and attending to their evolutionary path: poljes associated with relict valleys; poljes developed in abandoned valley sections, poljes related to the coalescence of BCS. The poljes expand by lateral solution planation, involving the retreat of the marginal slopes and their replacement by a polje floor controlled by the water table. The retreat of the slopes is mainly achieved by solutional undercutting during floods, mass movements, and the rapid removal of the gypsiferous landslide deposits.

The main factors that seem to favor the development of poljes in Sivas include: (1) a morphostructural trough with relatively low uplift rate that confined the path of the main drainages; (2) abundant aggressive water supplied by allogenic rivers; (3) a fluviokarst landscape including fluvial landforms that can transform into poljes; and (4) presence of clusters of bedrock collapse sinkholes that experience rapid expansion.

Gough's Cave has delivered some of Britain's most archaeologically significant human skeletal remains. Whilst Cheddar Man, the oldest near complete skeleton from Britain, may be most well known find at the cave, a less recognised but equally significant assemblage of human skeletal material could yet offer even greater insights into the behaviour of some of the UK's earliest human inhabitants.

The material in question dates to the late Upper Palaeolithic (LUP; 15kya) in Europe, a period of widespread population movement catalysed by the amelioration of glacial conditions in northern latitudes. The assemblage consists of lithic and worked bone industries characteristic of the Magdalenian culture, one of the two major human technocomplexes identified in Europe during the LUP. Two hundred and five human bone fragments are represented, the majority of which show anthropic modification (cutmarks, tooth marks and percussion damage) indicative of cannibalism, alongside three human cranial vaults that have been carefully modified to form skull cups. The abundance of faunal material and the high occurrence of cannibalised human remains at the site, alongside the identification of similar cannibalistic behaviour at other Magdalenian sites suggest that the behavior was ritual in nature, rather than having a nutritional basis.

Here, an overview of prior work performed on the LUP assemblage at Gough's Cave will be presented, alongside recent biomolecular results that include novel aDNA analysis. Through greater understanding of the ancestry and relationships of individuals deposited at the site, we seek to better contextualise the assemblage within the wider Upper Palaeolithic and further elucidate the complex behaviour identified at the site.

Mid-latitude alpine caves preserve a record of past solid precipitation during winter, locally spanning several centuries to millennia. Austria hosts more than 1200 perennial ice deposits registered in the national cave cadaster, some of which are exceptionally stratified, or contain evidence for millennial ice. Dating organic macro-remains trapped in ice layers with radiocarbon allows the determination of timing and duration of past periods of positive and negative ice mass balance.

In this talk, we present a comparative study of ice cave deposit chronologies, using Bayesian age over caves in the Austrian Alps. We show that periods of positive mass balance coincide with past glacier advances in Europe. The Medieval Climate Anomaly (between 850 and 1200 CE) marked widespread ice retreat on the surface; underground it is characterised by the presence of organic and macro-remain rich layers. We show evidence for positive ice mass balance at all studied sites during the Little Ice Age, at a time when the largest glacier advances in the Holocene were recorded. At the sites with records spanning over 2000 years, we find that the deposits experienced a positive mass balance periods from 300 BCE to 100 CE and 600–800 CE.

Today, these caves are thermal anomalies with respect to the surrounding rock temperatures and experience accelerated negative mass balances. Monitoring the main trends in their rock and air temperature records at a low-elevation ice cave of the Northern Calcareous Alps has allowed us to build a temperature-based mass balance model for one site and forecast the imminent demise of its ice deposit in the next decades.

Caves, groundwater, and other subterranean habitats harbor a diverse and significant fauna that provide significant economic and societal value (i.e., ecosystem services), from water purification and nutrient recycling to being important models for developmental and human health research. Yet, our knowledge of subterranean biodiversity is extremely limited and adheres to the idiom 'out of sight, out of mind.'

Most cave-obligate species are diminutive, non-charismatic, and occur in habitats that are literally hidden below the earth. Consequently, significant knowledge gaps exist related to true levels of diversity, distributions, abundance, evolutionary history, and life history of subterranean fauna. The ever-increasing risk of biodiversity loss from a plethora of threats, such as urbanization, groundwater pollution, and climate change, adds urgency to our need to understand the responses and resiliency of subterranean biodiversity in the face of environmental change.

Here I review cave and groundwater fauna in North America, including its diversity, importance, knowledge gaps, and conservation status. I also will discuss new approaches and initiatives to address these knowledge shortfalls and offer recommendations for future research and conservation and management efforts.