Dogwiler T. and Wicks C.
Abstract: This investigation quantifies how temperatures fluctuate in relation to discharge, seasonal, and diurnal temperature variations. Furthermore, the linkages between meteorological processes and temperature variation in the hyporheic zone are delineated. Examination of a high-resolution, three dimensional record of temperature variation in a karst stream substrate provides insight into thermal disturbances in the hyporheic zone. Temperatures in the upper portion of the hyporheic zone are strongly linked to air temperatures via the surface water. The variation is considerably less as depth increases. The annual temperature variation in the lower portion of the shallow hyporheic zone is reduced by one-third, relative to the variation observed in the surface water and upper substrate. During storm events, the upper portion (0-5 cm) of the shallow hyporheic zone is subject to a thermal regime very similar to surface stream water. However, below these depths the sharpest temperature fluctuations are effectively muted within the stream substrate. More frequent diurnal variations, particularly those associated with baseflow conditions, are also dampened within the substrate.
- Republished from: Quarterly Journal of Engineering Geology and Hydrogeology, 2003, vol. 36, pp. 101-118.
- PDF: /pdf/seka_pdf4513.pdf
Waltham A. C. and Fookes P. G.
Abstract: On a world scale, the dissolution of limestone and gypsum by natural waters creates extensive karst landforms that can be very difficult ground for civil engineers. Caves threaten foundation integrity, notably where their width is greater than their roof thickness. Sinkholes pose many problems, and are classified into six types, including subsidence sinkholes formed in soil cover within karst terrains. Rockhead morphology varies from uniform to pinnacled, also creating difficult ground to excavate or found upon. A proposed engineering classification of karst defines various complexities of ground conditions by the geohazards that they provide, mainly the caves, sinkholes and rockhead relief. Ground investigation techniques and foundation design philosophies are considered so that they are appropriate to the ground conditions provided by the different classes of karst.
- Republished from: Cave and Karst Science, 31 (3), 2004, 123-134.
- PDF: /pdf/seka_pdf4514.pdf
Abstract: There has much been speculation as to whether cave formation should occur at, above, or below the water table, but a satisfactory explanation has been lacking until recently. The last 50 years has seen extensive mapping of caves both above and, more recently, below the water table. It is now becoming apparent that there are systematic differences in depth of flow between different areas and that conduit flow to depths >100m below the water table is not uncommon. Such deep flow is facilitated by the lower viscosity of geothermally heated water at depth. Analysis of data from caves shows that depth of flow is primarily a function of flow path length, stratal dip and fracture anisotropy. This explains why conduits form at shallow depths in platform settings such as in Kentucky, at moderate depths (10–100m) in folded strata such as in England and in the Appalachian Mountains, and at depths of several hundred metres in exceptional settings where there are very long flow paths.
- Republished from: Acta Carsologica, 34 (1), 2005, 51-72.
- PDF: /pdf/seka_pdf4511.pdf
Abstract: There are few cases of open caves that have been reliably dated to ages greater than 65 Ma. This does not mean that such caves are extremely rare, rather it is difficult to reliably establish that a cave, or palaeokarst related to a cave, is this old. Relative dating methods such as: - regional stratigraphic, lithostratigraphic, biostratigraphic, relative climatic, relative isotopic, morphostratigraphic, and regional geomorphic are very useful. They suffer however from significant difficulties, and their results lack the impact of a crisp numerical date. While many of the methods used to date younger caves will not work over the required age range, some isotopic methods and palaeomagnetic methods have been applied with varying degrees of success. While finding something to date and having it dated is difficult enough, producing the date is rarely the end of the story. The difficult issue is not the date or relative correlation itself, but what the date or correlation means. Demonstrating that caves are ancient seems to rapidly become beset with the old adage that ?extraordinary claims require extraordinary proof?. The presence of a well-dated or correlated sediment in a cave does not necessarily mean that the cave is that old or older. Perhaps the dated material was stored somewhere in the surrounding environment and deposited much more recently in the cave. A lava flow in a cave must be demonstrated conclusively to be a flow, not a dyke or a pile of weathered boulders washed into the cave. It must be conclusively shown that dated minerals were precipitated in the cave and not transported from elsewhere. There seems little doubt that in the future more ancient caves, or ancient sections of caves, will be identified and that as a result our perception of the age of caves in general will change.
- Republished from: International Journal of Speleology 2004, 33 (1/4), 97-104.
- PDF: /pdf/seka_pdf4512.pdf
Abstract: A state of the art of the research on trace elements of speleothems is given. First studies focussed on problems such as the colour of speleothems and the aragonite problem. In-situ studies and studies oriented towards a better understanding of vadose hydrology brought new insights in the controls on trace elemental composition of speleothems. Recent studies deal with microscale analyses and annual and intra-annual chemistry changes. Further in-situ studies should be performed to further differentiate influences, such as climate, soil/weathering and local hydrology in order to better constrain possible transfer functions between the surface and a speleothem.