Paleoflood events recorded by speleothems in caves

Abstract

Speleothems are usually composed of thin layers of calcite (or aragonite). However, cemented detrital materials interlayered between laminae of speleothemic carbonate have been also observed in many caves. Flowstones comprising discontinuous carbonate layers form due to flowing water films, while flood events introduce fluviokarstic sediments in caves that, on occasion, are recorded as clayey layers inside flowstones and stalagmites. This record provides a potential means of understanding the frequency of palaeofloods using cave records. In this work, we investigate the origin of this type of detrital deposit in El Soplao Cave (Northern Spain). The age of the lowest aragonite layer of a flowstone reveals that the earliest flood period occurred before 500 ka, though most of the flowstone formed between 422 +69/‐43 ka and 400 +66/‐42 ka. This suggests that the cave was periodically affected by palaeoflood events that introduced detrital sediments from the surface as a result of occasional extreme rainfall events, especially at around 400 ka. The mineralogical data enable an evolutionary model for this flowstone to be generated based on the alternation of flood events with laminar flows and carbonate layers precipitation that can be extrapolated to other caves in which detrital sediments inside speleothems have been found. Copyright © 2014 John Wiley & Sons, Ltd.

In situ Raman characterization of minerals and degradation processes in a variety of cultural and geological heritage sites

“…6). These results agree with the mineralogy of flowstones and frostwork speleothems reported in previous studies of this cave [12]. Aragonite is a rather common mineral in dolostone caves such as El Soplao, where the dolomitic nature of the bedrock has been corroborated by Raman spectroscopy.…”

“…Spectacular helictites and huge speleothems are the most relevant aesthetic features of this mining show-cave [12]. Other unusual speleothems have also been described, including amberine stalactites [13], flowstones containing layers of cemented detrital materials [14], black ferromanganese crusts and stromatolites [15,16], frostwork-type speleothems and moonmilk deposits [17], some of which were studied in our in situ survey.…”

Extracting palaeoflood data from coarse‐grained Pleistocene river terrace archives: an example from SE Spain

“…These data are locked within a variety of fluvial-related archives (Figure 1) and the time range that these archives can be extended to is continually improving (e.g. Gázquez et al, 2014). Within terrace archives it is rare to be able to trace an individual flood event across a fragmentary terrace record.…”

Paleo-watertable definition using cave ferromanganese stromatolites and associated cave-wall notches (Sierra de Arnero, Spain)

“…Average initial 234U/238U activity ratios for the three speleothem sites with U-Th disequilibrium reported here are 3.74, 1.29, and 1.34 (Table 1), and 3.20 for stalagmite BO2 (Rossi et al 2010). Besides, we have calculated initial 234U/238U ratios for three subsamples of flowstone SPL in U-Th disequilibrium based on data by Gázquez et al (2014), resulting in a mean value of 1.33 for that flowstone. Therefore the average initial 234U/238U activity ratio for the five speleothems in U-Th disequilibrium is 2.39.…”

“…4A). Flowstone sample SPL-00 (after Gázquez et al, 2014) is also in U-Th secular equilibrium and grew in the main relict canyon too, overlaying clastic sediments that in turn cover ST3 stromatolites (Fig. 3A).…”