The origin of enigmatic, tubular, lake-shore karren:
A mechanism for rapid dissolution of limestone
in carbonate-saturated waters

Michael J. Simms, Department of Geology, Ulster Museum

Published in Physical Geography , vol. 23, pt. 1 (January 2003), pp.1-20

Abstract:Vertical, upward tapering, closed tubes (here termed röhrenkarren) have been observed in abundance in limestone exposed in the epiphreatic zone around several lakes in Ireland. Röhrenkarren form by condensation corrosion within air pockets trapped by seasonal floodwaters. This promotes rapid limestone dissolution where lake, or cave, waters are at or near saturation with respect to calcium carbonate. Their abundance testifies to the large-scale dissolution of limestone and simultaneous enhancement of carbonate precipitation in carbonate-saturated environments where dissolution directly by lake water is very limited. Lake-specific differences in röhrenkarren morphometry provide a unique record of the long-term water chemistry at each site. The underlying mechanism has implications for other solid-liquid interfaces.

The Carra-Mask-Corrib lake system supports the finest assemblages of röhrenkarren and associated lake-shore karst assemblages anywhere in Ireland. Other sites are indicated on the inset map (C=Lough Coy; D=Lough Derg; E=Lough Ennel; R=Lough Rea).

The distinct size assemblages in the Carra-Mask-Corrib system (see graph below) appear to correlate with the ratio of silicate to limestone catchments for each of the lakes, which influences the long-term water chemistry of each. Loughs Corrib and Carra are almost permanently saturated with carbonate, but Lough Mask sometimes becomes undersaturated.

Nonetheless, all lakes at which röhrenkarren have been found are at or close to saturation. They do not form in lakes where the water is significantly undersaturated for much of the time, such as in the Killarney lakes (K on the inset map)