�This paper presents the basic elements of a conceptual model for the development of epikarst in US mid-continent, horizontally-bedded carbonates in which flow is largely confined to secondary and tertiary porosity. The model considers the development of epikarst regimes in carbonate sequences beginning shortly after non-carbonate rocks are eroded away to expose the underlying carbonates and follows this through capture of the shallow flow by deeper dissolution conduits with reorientation of the epikarst to a more vertical form. The model does not require an underlying zone of vadose flow and in many cases considers development of such a zone to depend on the water supply provided by prior development of the epikarst. It is not claimed that all epikarsts form in the accordance with this model; rather this paper presents a viable additional model for epikarst formation under appropriate starting conditions. Factors influencing the development of epikarst are a combination of: 1) the pre-karst topography and modifications to this as the system evolves, 2) the original distribution and aperture of fractures as well as the distance and orientation of physically favorable fractures relative to potential discharge points, such as existing dissolutionally-enhanced channels with low head or nearby valleys, 3) character of soil cover as this affects percolation of water to the rock, erodability of the soil, sediment filling of conduits, and transport of sediment 4) variations in availability of dissolutionally aggressive water with time and location, and 5) low solubility layers, such as shale or chert, that promote lateral flow until a penetration point can be found. These interact to form an epikarst and deeper karst system that progressively increases its capacity both by internal improvement of its flow routes and extension into adjacent areas. The availability of water needed to promote dissolution also often has a positive feedback relationship to epikarst, in which locations of most active dissolution modify their vicinity to progressively increase capture of water, which promotes further dissolution. In early stages, lateral flow through the overlying soils and along top-of-rock must dominate the groundwater flow because the relatively intact carbonates have insufficient transmissivity to convey the available recharge through the body of the rock. Top-of-rock runnels developed by a combination of dissolution of their floors and piping erosion of their roofs would carry a significant portion of the flow. Horizontally-oriented epikarst develops with discharge to local drainage. Cutters and pinnacles, collapse-related macropores, and areas of concentrated recharge would begin to form at this stage. Initial downward propagation of this system would occur mostly due to lateral flow. Mixing corrosion could occur in sumps in these lateral flow routes when fresh, percolating rainwater mixes with older water with a higher dissolved load. Should conditions be suitable, leakage from this system promotes the migration of deeper karst conduits into the area by Ewers multi-tiered headward linking. Other sources of water may also bring in such deeper conduits. Once such deeper conduits are present, the epikarst can evolve into a more vertically oriented system, at least in the vicinity of master drains into this deeper system. Former shallow epikarst routes may then plug with sediment. In some areas, deeper systems may never develop due to unfavorable conditions. The epikarst may be the only significant system in these cases. This includes the case of poor karst formers such as interbedded shales and carbonates that may have very shallow horizontal epikarst flow paths that channel shallow subsurface flows.

Central Asia is currently a semiarid-arid region, dominated by the Westerlies. It is important to understand mechanisms of climate and precipitation changes here, as water availability in the region is crucial today and in the future. High-resolution, absolutely-dated oxygen isotope (d18O) records of stalagmites from Kesang Cave characterize a dynamic precipitation history over most of the past 500,000 years. This record demonstrates, for the first time, that climate change in the region exhibits a processional rhythm with abrupt inceptions of low d18O speleothem growth at times of high Northern Hemisphere summer insolation followed by gradual d18O increases that track decreases of insolation. These observations and interpretations contrast with the interpretation of nearby, but higher elevation ice core records. The absolutely-dated cave d18O shifts can be used to correlate the regional climate variability by providing chronological marks. Combined with other paleoclimate records, the Kesang observations suggest that possible incursions of Asian summer monsoon rainfall or related moisture into the Kesang site and/or adjacent areas during the high insolation times may play an important role in changing orbital-scale hydrology of the region. based on our record, arid climate will prevail in this region for the next several millennia, providing that anthropogenic effects do not supersede natural processes.

Carbonate rocks of upper Cretaceous, Paleocene and Eocene crop out in cuesta escarpments in different sectors of the eastern part of the Inner Range of the Crimean fore-mountains. Scarps and adjacent strips of the plateaus demonstrate a set of features, characteristic and unique for the Crimean fore-mountain region, represented by various conduit and cavernous forms (karstified fractures, grottoes, niches, caves, vugs and zones of vuggy porosity), sculptured surfaces and honeycomb, boxwork and spongework surfaces of scarps, and also by couloirs and blind valleys in the near-scarp strips of structural slopes. The paper demonstrates that all these forms are relics of the morphology of sub-vertical hypogenic rift-like conduits, their meso-elements and forms of the vuggy fringe, exposed due to the scarp retreat by block toppling. Previous ideas of the formation of grottoes and niches in scarps by processes of external weathering and gravitational destruction are shown to be inadequate, and the hypogenic karst origin of these forms is firmly established. The analysis of distribution and morphology of relict hypogenic karst features has allowed reconstructing the structure and functioning of hypogenic karst systems, which had been formed by dissolution and metasomatic alteration of host rocks under confined conditions, along cross-formational tectonic fractures organized in linear corridors and clusters. Interaction of rising fracture-vein waters of the deep circulation system with intra- and interstratal waters of shallower systems played a particular role in hypogenic speleogenesis. It is shown that hypogenic karst was one of the primary factors of regional geomorphic development as it determined locations and morphology of the cuesta escarpments, as well as further landform development in the adjacent areas of the structural surfaces.

The persistent drought of the 2012 summer in the Midwestern United States significantly impacted the health and vigor of Illinois’ crops. An unforeseen outcome of the extreme drought was that it provided a rare opportunity to examine and characterize the bedrock surface and underlying karst aquifer within the Driftless Area of northwestern Illinois. Complex networks of vegetated lines and polygonal patterns, herein referred to as crop lines, crisscrossed the dry summer landscape of Jo Daviess County. Initially, the crop lines were examined and photographed using a handheld digital camera on the ground and from a small aircraft at 300 meters altitude above ground level (AGL). The orientations, widths and horizontal separations of the lines were measured. Crop lines and their patterns and orientations were compared with those of crevices in outcrops, road cuts and quarries, and with lineaments seen in LiDAR elevation data of Jo Daviess County.
Primarily confined to alfalfa fields and, to a lesser extent, soybeans and corn, the crop lines are the result of a combination of extremely dry conditions, and a thin soil zone overlying fractured and creviced Galena Dolomite bedrock. The plants forming the lines tend to grow denser, taller (0.5 m vs 0.15 m) and darker/greener than those in adjacent areas. Alfalfa taproots are the deepest of the aforementioned crops extending up to 7 m below the surface. Groundwater and associated soil moisture within the vadose zone present within bedrock fractures and crevices provide the necessary moisture to sustain the overlying healthy plants, while the remaining area of the field exhibits stunted and sparse plant growth. Overall, the crop lines are a reflection of the creviced pattern of the underlying karst bedrock and associated karst aquifer, and reveal the degree and extent of karstification in eastern Jo Daviess County. The crop lines were consistent with the angular lines of adjacent streams that show a rectangular drainage pattern. Stream patterns like these are well known and are due to drainage controlled by crevice/fracture patterns in the top of bedrock. The lines appear to have been formed by two sets of fractures trending roughly north-south and east-west with occasional cross-cutting fractures/crevices. The east-west trending lines are consistent with tension joints, and the north-south lines are consistent with the shear joints identified by earlier researchers. The trends of the crop lines, tension and shear joints are similar to those of lineaments identified from LiDAR elevation data in the same area (N 20° W, and N 70° W and N 70° E) and coincide with the occurrence of karst features throughout eastern Jo Daviess County.The pattern observed in the crop lines closely mimics the fracture/crevice patterns of the bedrock surface. The widths and extent of the lines may be used as a surrogate for the karst features present on the bedrock surfaces. Crop lines, coupled with solution-enlarged crevices seen in bedrock exposures, yield a three dimensional view of the bedrock crevice-fracture system, and ultimately could provide a more complete and accurate model of the karst aquifer in the study area and similar karst areas in the Midwestern United States and perhaps in other karst regions of the world.