#1 — Mon 08 Jan 2024 ▼ 

Caves, Dinosaurs and the Carnian Pluvial Episode

With: Mike Simms, Senior Curator Natural Sciences, National Museums Northern Ireland
Time: Mon 08-Jan 2024, 19:30 to 21:00 GMT.
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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.

#2 — Mon 05 Feb 2024 ▲ ▼ 

Tracking alpine cave glaciations: cryogenic cave carbonates from the Eastern and Southern Alps

With: Gabriella Koltai, Innsbruck Quaternary Research Group
Time: Mon 05-Feb 2024, 19:30 to 21:00 GMT.
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Coarse crystalline cryogenic cave carbonates (CCC for short) form via freezing-induced supersaturation of small karst water bodies within cave ice when cave air temperature is slightly below 0°C. Currently CCC are the best and sometimes single evidence for former glaciation of caves. Their age can be accurately determined by the 230Th dating method, and thus these unique speleothems can be used to reconstruct the time when ice was present in a particular cave section all year round. However, due to their commonly small size CCC have been overlooked in caves compared to other types of speleothems. Recently CCC have been found in a dozen of currently ice-free caves in the Eastern and Southern Alps, suggesting that these speleothems are probably more common than previously thought. In this seminar I will share some highlights from alpine caves and demonstrate how these deposits can be used to reconstruct multiple episodes of cave glaciation during the last glacial period.

#3 — Mon 11 Mar 2024 ▲ ▼ 

The evolution of the poljes and sinkholes in the Sivas gypsum karst, Turkey

With: Ergin Gökkaya, Niğde Ömer Halisdemir University, Turkey
Time: Mon 11-Mar 2024, 19:30 to 21:00 GMT.
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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.

#4 — Mon 08 Apr 2024 ▲ 

The Archaeology of Caves in the Burren, Co.--Clare,--Ireland

With: Marion Dowd, Atlantic Technological University, Sligo, Ireland
Time: Mon 08-Apr 2024, 19:30 to 21:00 BST.
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At present, 15 caves in the Burren are protected archaeological sites with evidence of human activities underground spanning at least 4,500 years. This talk will explore how people from the Neolithic (Stone Age) through to post-medieval times used and perceived caves in this distinctive landscape. It was during the later Bronze Age (c. 1000–600 BC), in particular, that cave usage increased, with evidence for elaborate ritual and religious practices. The early medieval period (c. AD 800–1100) saw extensive use of caves for occupation, storage and as hideaways. Folklore, as well as the more recent activities in caves associated with the Irish War of Independence (1919–1921), will also be examined.

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