Abstract The limestone caves of Stoney Middleton Dale are a Site of Special Scientific Interest (SSSI) for features of geological interest, but have been open access since at least the eighteenth century and have a documented history of geotourism. Using the examples of Carlswark Cavern and Merlin Cavern, this chapter sets out evidence that 300 years of open access has resulted in significant disturbance to the features of geological interest. In particular, the integrity of the overall site for scientific research was affected by historical removal of speleothem formations long before it became a SSSI, with damage still occurring today. As most cave SSSIs in Derbyshire have historically had similar open-access arrangements, the examples presented highlight that there is potential for the integrity of less well historically documented caves elsewhere to have been disturbed. This article highlights the importance of establishing a baseline of historical disturbance to recognize whether the integrity of cave SSSIs have been affected and help monitor if disturbance is still occurring. For cave SSSIs to be useful for geological research, it is suggested that there is a need for the historical legacy of open access to individual caves elsewhere to be better understood.

Speleothems are valuable archives of climate change because of their extraordinary time resolution, which is unattainable in other terrestrial climate proxies. Analyses of 4796 ultraviolet fluorescent (UVf) layers observed in polished thin sections of a 15-cm-long speleothem collected from Raccoon Mountain Cave near Chattanooga, Tennessee, USA, as well as 200 δ 13 C and δ 18 O measurements and 11 high-precision U/Th dates permit refined interpretations of middle and late Holocene paleoclimate records in the southeastern United States. Speleothem UVf layers average 0.015 mm, identical to the average growth rate determined for the middle and late Holocene portions of the speleothem (ca. 7600–400 yr B.P.) based on the U/Th ages and interval thicknesses. UVf layer counts between paired U/Th ages are also consistent with determined ages and further support their interpretation as annual layers. The middle Holocene is typified by 100–400 yr intervals of higher rainfall characterized by thin UVf layers (0.003–0.010 mm) and more-negative δ 13 C values (−3‰ to −6‰ Peedee belemnite [PDB]), punctuated by shorter periods (5–20 yr, rarely 50–100 yr) of lower rainfall with thicker UVf layers (0.030–0.080 mm) and less-negative δ 13 C values (−1‰ to −3‰ PDB); “extreme drought” events are characterized by both the thickest UVf layers (0.150–0.170 mm) and the least-negative δ 13 C values (+0.05‰ to −1‰ PDB). The late Holocene, in comparison, is characterized by overall wetter conditions and more regular (sinusoidal curve) behavior, suggesting 50–100 yr cycles of higher and lower rainfall, with UVf layers ranging from 0.005 to 0.030 mm/yr. Statistical analyses of UVf layer thicknesses using order-two momentum threshold vector autoregressive models (MTVAR2) quantify the relationship between δ 13 C and δ 18 O, dependent upon the momentum in the climate. This study demonstrates that thickness of annual layers in speleothems can be used to resolve detailed paleorainfall records, provided there is preservation of organic matter sufficient to excite UVf response; however, relationships among changes in rainfall amounts, stable isotope values of speleothem calcite, and thicknesses of UVf annual layers (≈growth rates) are not straightforward.

ABSTRACT On a regional geological map, western Wisconsin looks as if it has very simple, even boring, geology. It is dominated by flat-lying, layer-cake Ordovician sedimentary rocks thinly overlain by Pleistocene glacial drift, yet detailed investigation reveals many interesting geologic features, furnishing research projects and teaching examples for all levels of geological education. In this “simple” area around Spring Valley, Wisconsin, you will see a major cave, an old mine, a large earthen dam and a meteorite impact site. In addition to what these sites say about the area’s geologic and human history, they furnish insight into how geologists piece together evidence as well as illustrate relevant subjects such as groundwater supply, control of catastrophic flooding and intelligent land use. It is our hope that, while enjoying learning about the features in this scenic part of Wisconsin, many of you will be inspired to seek out the unique geology of your area, and bring that knowledge into your classrooms.

Abstract Pyrometamorphism of coal measures that overlie underground burnt-coal seams in the southern area of the Rotowaro coalfield, New Zealand, has produced porcellanites that enclose lenses of iron-rich magnetite and hematite-bearing slag-like rocks, which show various degrees of oxidation. Paralavas that are associated with the iron-rich lenses form stalactites around fissures and gas-escape vents and intrude the porcellanites. The slags are unusually rich in iron and contain magnetite, hematite, hercynite, titaniferous magnetite, and minor fayalite and silicate glass. Iron oxides in these rocks exhibit a variety of textures and morphologies, including dendritic, quench, exsolution, and oxidation. The paralavas contain abundant glass, which encloses feathery crystals of fayalite and orthoferrosilite, plagioclase, tridymite, cristobalite, and minor magnetite. Phase-equilibria data indicate that the paralavas and slags were formed at temperatures in the range of 1000–1600 °C. Composition plots of local coal measure sediments, a siderite nodule, and various porcellanites, slags, and paralavas with respect indicate that the porcellanites are iron-rich when compared to SiO 2 , Fe 2 O 3 , and Al 2 O 3 with the unmetamorphosed coal measures. The slags, irrespective of their oxidation state, plot on the iron-enrichment trend shown by the porcellanites. Although the siderite nodule lies within the iron-enrichment trend, most of the slags are more iron-rich than the siderite nodule. The paralavas diverge from the iron-enrichment trend, suggesting that they formed by partial melting of the porcellanites. The Rotowaro samples represent some of the most iron-rich natural slags collected from a combustion-metamorphic environment to date.

The eastern flanks of Mount Elgon, an early Miocene stratovolcano, host caves (∼150 m long, ∼60 m wide, ∼10 m high) of debatable origin. Many animals, primarily elephants, “mine” the pyroclastic bedrock for sodium-rich salts. Speleogenesis has been argued to be primarily zoogeomorphic, or primarily dissolutional with only minor zoogeomorphic modification. This report provides the first detailed mapping and geomorphological study of the caves. Speleogenesis is polygenetic and strongly related to lithology. Geological units are, from the top down, ∼2 m of dense pyroclastic agglomerate cap rock over which water falls, ∼10 m of more permeable agglomerate, up to ∼0.2 m of discontinuous impermeable lava, ∼2 m of very soft and permeable agglomerate, and >2 m of impermeable swelling-clay tuff. Caves develop behind waterfalls under surface stream valleys by sapping of the incompetent agglomerate above the clay, and failure of the clay (aquiclude and base level for speleogenesis), followed by collapse of harder agglomerate layers above. The dominant passage shape is breakdown dome, with abundant fresh collapse. Geophagy by elephants and other species, and human mining significantly modify and enlarge the caves and remove collapse debris. These activities, focused on accessible and salt-rich units, create quasi-horizontal undercuts (up to ∼4 m tall and deep), the loci of which move upward as collapse raises the floor. Significant erosion also occurs by incongruent dissolution, corrosion, pressure release, efflorescence flaking, and biogeochemical activity from huge bat colonies. No evidence was found of channeled flow, or of phreatic or vadose activity. These caves are probably no older than Holocene.

The Nullarbor Plain of southeastern Australia, ∼200,000 km 2 in area, is flat and mostly treeless. It contains widely scattered collapse dolines and a few hundred caves, some of which are large and extensive. Initial karst development probably occurred during the warm, seasonally wet climatic conditions of the Oligocene, when the withdrawal of the sea exposed the recently deposited Eocene Wilson Bluff Limestone for over ∼10 m.y. Several major conduits probably developed at this time. These were flooded by the return of the sea, which finally retreated in the late Miocene followed by regional uplift. Cave formation in the Pliocene and Quaternary was inhibited by the semiarid climate, which became increasingly arid ca. 1 Ma. The overall dryness caused crystallization of evaporite minerals in cracks and pore spaces within the limestone walls of the caves, and they suffered extensive collapse, producing large passages, dome chambers, and dolines. However, during a wet phase 5–3 Ma, rivers extended across the karst plain, and caves formed where they sank into the limestone. Shallower caves probably also formed at this time, perhaps associated with perched water tables. The Nullarbor Plain did not develop extensive surface and underground karst features, even during the wetter climate of the Oligocene. It appears that the flatness of the plain and the particular characteristics of the limestone (primary porosity and lack of jointing and inception horizons) resulted in relatively uniform downwasting and little cave formation. Climate played a relatively minor role in restricting karst development.

Deep phreatic shafts and travertine-capped sinkholes characterize Sistema Zacatón, an isolated karst area in northeastern Mexico. At a depth of at least 329 m, El Zacatón is the deepest known underwater pit in the world. Hypogenic karst development related to volcanism is proposed to have formed El Zacatón and is thought to have diminished since the late Quaternary peak activity. The resulting geomorphic overprint of Zacatón displays features similar to hydrothermal groundwater systems throughout the world. Other karst areas in northeastern Mexico are known for deep pits and high-flow springs rising from great depths, but differ from Zacatón in the speleogenetic processes that developed the caves. Sótano de Las Golondrinas (378 m), 200 km to the southwest of Zacatón, is among the deepest air-filled shafts in the world. The Nacimiento del Río Mante, 100 km to the west, is a large artesian spring that extends a minimum of 270 m below the water table. Although these three world-class karst systems all formed in Cretaceous limestone and are located relatively close together, there are significant differences in lithology, tectonic setting, and geomorphic features. Geochemical, microbiological, and geomorphologic data for Zacatón indicate that cave formation processes are similar to those observed in other volcanically influenced systems.

The high carbonate island of Niue has attracted the attention of scientists since the early European exploration of the South Pacific, but its extensive karst and numerous caves have so far received little attention. Our investigation recognizes two main types of caves on Niue: (1) steeply inclined, terraced, flank-margin caves that formed at the seaward edge of a migrating freshwater lens and that breach the vertical cliffs on the leeward side of the island, and (2) flat-roofed, water-table caves consisting of interconnected passages that developed at the paleo–water table and contain dissolution features caused by alternating vadose and phreatic conditions. The Niuean caves contain a large variety of both active and fossil speleothems, the forms and styles of which are controlled by the hydrodynamics of vadose and phreatic waters, the physical properties of the carbonate cap, and the tectono-eustatic history of the island. The stalagmites are composed exclusively of calcite and show pronounced laminations consisting of alternating light and dark couplets, likely representing austral summer and winter growth, respectively. The mean growth rate of stalagmites from coastal flank-margin caves (∼0.34 mm/yr) is faster by about a factor of 1.5 relative to stalagmites from inland water-table caves. In general, vadose and phreatic waters fall on the regional δ 18 O-δD meteoric water line, and their dissolved carbon is primarily derived from soil CO 2 . A material balance suggests that cave deposits act as sinks for Mg, Sr, Na, and CO 2 during the recharge of the aquifer. The Niuean caves and their speleothems offer exceptional opportunities for investigating problems bearing on the regional tectono-eustatic history and paleoseismicity of the neighboring Tonga Trench, and answer questions concerning the prehistoric rhythms and irregularities of El Niño–Southern Oscillation.

A handful of investigative teams in several parts of the world are studying abundant biological communities in caves formed by sulfuric-acid speleogenesis. These caves are atypical in terms of origin, chemistry, and ecosystem properties. They prominently display sulfur minerals, characteristic cavity topologies, and notable biological diversity and biological productivity resulting directly from the conditions that produce the caves. Even long-inactive systems still harbor some of these indicators. The microbial and macroscopic ecosystems within sulfuric-acid speleogenetic caves are geologically mediated and maintained. This geological mediation is a theme connecting them with other sulfur-driven ecosystems on Earth, including deep-sea hydrothermal vents, sulfurous near-surface hydrothermal systems, and solfataras. Evidence exists for potentially significant microbial participation in the process of speleogenesis itself. Recent results confirming the high relative abundance of sulfur on Mars, an apparent sedimentary basin with high sulfate concentration, near-surface indicators of ice and water, and trace detection of reduced gases (especially methane) in the Martian atmosphere, possibly deriving from subsurface microbial sources, set the stage for suggesting that sulfuric-acid speleogenetic systems may be useful as astrobiological analogs for hypothetical Mars ecosystems. Unique speleogenetic mechanisms may occur on Mars and could provide subsurface void space suitable for habitation by such hypothetical microbial systems.

North American research on surface karst landforms has tended to focus on factors affecting the development and distribution of sinkholes. There have been important quantitative contributions to understanding the formation of solutional, suffosional, and collapse sinks, and a major series of applied geotechnical studies has been published. Gypsum karst, and the impacts of repeated glaciations and permafrost on carbonate, gypsum, and salt karst have received much attention in recent years. North American research dominated the general field of speleogenesis until the past two decades. There are well-understood models for dissolutional cave development in young, newly emerged limestones, for situations where cool or thermal waters ascend from deeper formations, and for descending, unconfined meteoric waters. Worldwide, there is now intensive computer modeling of conduit initiation and enlargement and their relation to the evolution of karst aquifers. There have been many important advances in the study of cave deposits. Clastic sediments may be dated approximately by paleomagnetics, more precisely by cosmogenic 10 Be/ 26 Al decay of quartz sands or pebbles, and by 39 Ar/ 40 Ar where clays have been converted to alunite by H 2 S reactions. Currently, there is a bandwagon in paleoenvironmental studies of speleothems. They can be precisely dated back to 500,000 yr B.P. by U-series methods, their C and O isotope ratios track local and regional environmental changes over the course of the glacial cycles, and many display annual or other significant periodic banding.

Cave, spring, and sinkhole development in the Ozarks of south-central Missouri is placed in a geologic framework through detailed geologic mapping. Geologic mapping shows that initial dissolution and inception of cave development is concentrated just beneath sandstone beds within Upper Cambrian and Lower Ordovician dolostone. Although rocks of the Ozarks have systematic and pervasive vertical joints, the development of karst conduits is controlled by bedding planes and stratigraphic variability. In the Salem Plateau of south-central Missouri, sinkholes occur in the lower part of the Ordovician Roubidoux Formation, where sinkholes are rimmed with and contain sandstone that has collapsed into voids in the underlying Ordovician Gasconade Dolomite. Cave diving by the Ozark Cave Diving Alliance into Alley Spring, a large (average flow 3.7 m 3 /s) spring along the Jacks Fork in the Ozark National Scenic Riverways, shows that although the spring discharges from the middle part of the Gasconade, the source of water is a cave passage just beneath the Gunter Sandstone Member of the Gasconade Dolomite. Artesian conditions cause the upward movement of groundwater from cavernous dolostone beneath the sandstone aquitards to the large springs. We hypothesize that sandstone, which is largely impermeable due to silica cementation, acts as a confining unit where hydraulic pressure, combined with mixing of water of differing chemistry, increases dissolution in the underlying dolostone beds.

Extensive flooded cave systems are developed in a zone 8–12 km inland of the east coast of the Yucatan Peninsula, Quintana Roo, Mexico. In plan, the systems comprise cross-linked anastomosing networks composed of horizontal elliptical tubes (which are actively developing where associated with the present fresh water/saline water mixing zone) and canyon-shaped passages. Both forms are heavily modified by sediment and speleothem infill, and extensive collapse. The pattern of Quintana Roo caves differs both from the mixing chamber form of flank-margin eogenetic caves, and also the dendritic and rectilinear maze patterns of epigenetic continental (telogenetic) caves. Unlike the latter, Quintana Roo caves are formed by coastal zone fresh water/saline water mixing processes. While mixing dissolution is also responsible for development of flank-margin caves, these may be typical of small islands and arid areas with limited coastal discharge, whereas Quintana Roo–type caves are formed when coastal discharge is greater. In the Quintana Roo caves, multiple phases of cave development are associated with glacio-eustatic changes in sea level. Two critical conditions control cave development following lowstands: (1) if the passage remains occupied by the mixing zone and connected to underlying deep cave systems, and (2) for passages above the mixing zone, if active freshwater flow is maintained by tributaries. In the first case, inflow of saline water drives mixing dissolution, enabling removal of the lowstand carbonate fill and continued passage enlargement. In the second, despite limited dissolution in the fresh water, continued removal of uncemented sediments can maintain the cave void. Where neither of these conditions is met, enlargement will cease, and the cave void will become occluded by collapse and sediment infill.

A coordinated textural, stable isotopic, and elemental investigation of calcitized speleothems was carried out to delineate the diagenetic transformation of unstable aragonite to stable low-Mg calcite. Many aragonite speleothems in certain limestone caves in Korea (Baekgol Cave, Jungteogeori Cave, and Chilsong Cave) have been partially calcitized. The neomorphic calcite crystals vary in size from tens of microns to a few millimeters. Numerous relic aragonite crystals and relic growth lines are present within the neomorphic calcites. Original calcite speleothems (i.e., initially deposited as calcite) tend to be more depleted in Sr and enriched in Mg than the original aragonite, and trace-element compositions of the neomorphic calcites approach their original aragonites. Also, O- and C-isotope compositions of the neomorphic calcite show similar ranges to those of the original aragonite. This suggests that the calcitization within the speleothems occurred in a semiclosed diagenetic system with respect to trace elements and oxygen isotopes. Diagenetic trends strongly suggest that stable isotopes and trace elements of the original aragonite were remobilized during calcitization. Unaltered aragonite speleothems in the Jungteogeori Cave are enriched in 13 C compared to original calcite speleothems, which may indicate that calcite speleothems were influenced more by soil-derived meteoric water during speleothem growth or that aragonite speleothems were deposited from cave water that was more buffered by carbon derived from the surrounding limestone. The 18 O enrichment observed in original aragonite speleothems compared to original calcite speleothems may imply that the aragonite speleothems were formed by evaporation under less humid conditions.