Freshwater Cave

The water phase of oil-base mud can be freshwater, or various solutions of calcium chloride (CaCl ) or sodium chloride (NaCl). The concentration and composition of the water phase in oil-base mud determines its ability to solve the hydratable shale problem. Oil-base muds containing freshwater are very effective in most water-sensitive shales. The external phase of oil-base mud is oil and does not allow the water to contact the formation the shales are thereby prevented from becoming water wet and dispersing into the mud or caving into the hole. 

This is set deeply enough to protect the borehole from caving-in in loose formations frequently encountered at shallow depths, and protects the freshwater sands from contamination while subsequently drilling a deeper hole. In case the conductor string has not been set, the surface casing is fitted with casing head and BOP. 

Chung GS, Swart PK (1990) The concentrahon of ttranium in freshwater vadose and phreatic cements in a Holocene ooid clay a method of identifying ancient water tables. J Sediment Petrol 60 735-746 Cliff RA, Spotl C (2001) U-Pb dahng of speleothems from the Spannagel Cave, Austria. XI EUG... 

The oldest loess-like sediments referable to the Lower Pleistocene have been found in Hungary at locality no. 5 at Vill ny, locality no. 4 imbedded in the freshwater limestone of Dunaalmds and locality no. 2 at Somssich Hill. These rocks, however, cannot be considered as typical loess because originally they were situated in cracks and crevices or deposited on freshwater limestone. They thus show a somewhat intermediate character, similar to cave loess. Similarly, we may refer the Lower Pleistocene material of the yellow layers of locality no. 8 at Villany to cave loesses (Kretzoi, 1956), in which the fauna elements indicate a cool, dry environment at the time of deposition. 

Worthy Park I Cave, Jamaica (Fig lb), is very similar to Wallingford Roadside Cave. The fossil-bearing deposit is an indurated clay plastered onto the walls of the entrance chamber, containing bones of Clidomys together with remains of freshwater turtle and frogs. The deposit is partially overlain with a flowstone that has yielded a U/Th age of 174 +13, -12 ka, which places it in marine isotope stage 6 (McFarlane et al., 1998). 

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