From fabric microstratigraphy of stalagmites to environmental changes affecting the process of calcite precipitation. A case study from two caves in N Spain.

Abstract

Speleothems have been broadly studied as archives of the Quaternary climate. One of the proxies preserved in stalagmites corresponds to the stratigraphic patterns of carbonate microfabrics. These fabrics are strongly dependent of a wide range of factors that include environmental parameters from outside the caves (such as rainfall, vegetation type, and soil thickness), from the epikarst (residence time of the water in the aquifer and water-rock interactions) and from within the cave itself (e.g. humidity, microbial activity…). As these are modulated by global, regional, and local climatic/environmental changes, the fabric microstratigraphy of the speleothems can be used as a tool for their reconstruction.

In the last few years, some progress has been done in the task of deciphering speleothem microstratigraphy (Muñoz-García et al., 2006; Martín-Chivelet et al., 2013). Lately, Frisia (2015) has summarized her previous works to generate a method for obtaining “standardized” microstratigraphic logs of fabrics to allow comparison of records obtained from different stalagmites. The codes proposed by Frisia (2015) comprise all the so-far known microfabrics in calcitic and aragonitic stalagmites and flowstones. Hence, the factors invoked to explain the genesis of the different fabrics are of very different nature (drip rate, Mg concentration, presence of organic matter…).

This work aims to test this method in four calcite stalagmites that present only some of the most common fabrics. This designedly narrowing in the variety of fabrics allows introducing a slight alteration to the codes proposed by Frisia (2015) in order to obtain microstratigraphic logs that can be related to changes in humidity only, likely derived from shifts in the hydric balance above the cave. This enhances the possibility of comparing these logs with independent proxies, such as stable isotope or trace element records. The studied specimens were recovered from two different karst systems: Sierra de Atapuerca and Ojo Guareña, both located in the province of Burgos, in northern Spain. For this preliminary test of the method a relatively short period of time has been selected (2200 to 900 yr BP).

From fabric microstratigraphy of stalagmites to environmental changes affecting the process of calcite precipitation. A case study from two caves in N Spain.. Available from: https://www.researchgate.net/publication/275330090_From_fabric_microstratigraphy_of_stalagmites_to_environmental_changes_affecting_the_process_of_calcite_precipitation._A_case_study_from_two_caves_in_N_Spain [accessed Apr 29, 2015].