Vein cavities in the Castleton caves: further information

In this study, stalagmites have been observed to be forming underwater. The stalagmites are found within a flooded horizontal mine adit, where the poolwater is supersaturated with calcite. Pool and drip water chemistry and hydrology were analysed over an annual field cycle. Stalagmite formation was observed to be from drip waters both undersaturated and supersaturated with calcite. Stalagmites were composed of calcite, and were poorly consolidated: all samples were compact on the side faces but several were unconsolidated underneath the splash impact point. Stalagmite morphology varied with drip fall height and overlying water depth. SEM and XRD analyses demonstrate that the stalagmites comprise calcite crystals of 50-200(mo)m, and show no evidence of biogenic particles or binding. Subaqueous stalagmite formation can be postulated to be caused by the disturbance of the impacting drip of surface calcite rafts formed due to degassing and/or evaporative processes, as well as possible calcite precipitation from the mixing of waters at the drip impact point. The stalagmites form by the slow accumulation of calcite crystals, with occasional collapses until a stable structure is formed, which can ultimately be preserved in the rock record. The stalagmites observed in this study can be considered to be an example of the chemogenic precipitation of calcite by a combination of chemical and physical processes. Such evidence has been rarely reported before in either freshwater or marine environments, and should be preserved in palaeokarst environments.