Dating cave drip water by tritium
Using concentration differences between this infiltration-weighted mean and the drip water, an age is calculated from the radioactive decay law, assuming piston flow.The approach was tested in three adjacent caves in northwestern Germany which were monitored for about two years.Significant karstification, including the development of caves, can occur over timescales of 10-rich percolating water and the formation of speleothems.In these settings, drainage of infiltrating water tends to occur sub-vertically (Figure 1), but is principally guided by networks of fractures (or bedding, where it is inclined).Many carbonates become tightly cemented, and are sometimes dolomitized, during burial, but then are exposed to karstification by freshwater when they are uplifted.When freshwater contacts carbonate, particularly where carbon dioxide pressures are raised in soil zones, calcium carbonate dissolution occurs.The properties of these rocks significantly influence the delivery of water that supply the raw ingredients for speleothem growth, and hence our focus in this article on dripwater hydrology.
Carbonate sediments are converted to rocks by sets of diagenetic processes in marine, meteoric, or burial environments.
This enables water storage to occur such that in some slow-flowing drips, mean water ages deduced from tracer studies may reach periods of years (Kluge et al. This figure is based on a hypothetical cave in pre-Mesozoic bedded limestone which has undergone folding and which contains paleokarstic, lithified caves.
Stalagmites (A, B, C and D) are all fed by different flow pathways.
All of the studied drip sites yielded drip water ages between 2 and 4 years with uncertainties on the order of 1 year.
These results were confirmed at several drip sites by oxygen isotope data which show rather constant values with insignificant intra-annual variability.
All three caves may vary in their size and the way they fill with water and subsequently drain.