The Ernesto Cave, northern Italy, as a candidate auxiliary reference section for the definition of the Anthropocene series

Abstract

Annually laminated stalagmites ER77 and ER78 from Grotta di Ernesto provide an accurate annual record of environmental and anthropogenic signals for the last ~200 years. Two major transitions are recorded in the stalagmites. The first coincides with the year 1840 CE, when a change from porous and impurity-rich-laminae to clean, translucent laminae occurs. This is accompanied by a steady increase in the growth rate, a decrease in fluorescence and a sharp increase in δ13C values. These changes concur with the end of the Little Ice Age. The second transition takes place around the year 1960 CE and corresponds with an increase in both annual growth rate and sulfur concentration in stalagmite ER78 at 4.2 mm from the top, and with the deflection point in the 14C activity curve in stalagmite ER77 at 4.8 mm from the top. This latter is the stratigraphic signal proposed as the primary guide for the definition of the Anthropocene series. The following shift toward depleted δ34S–SO4 in stalagmite ER78 suggests that industrial pollution is a major source of sulfur. The interpretation of atmospheric signals (S, δ34S, 14C) in the stalagmites is affected by attenuation and time lags and the environmental signals are influenced by soil and ecosystem processes, while other anthropogenic signals (δ15N, 239Pu) are not recorded. For these reasons, the stalagmite record is here proposed as an auxiliary (reference) section rather than a global standard. In summary, Grotta di Ernesto contains one of the best stalagmite records documenting the Anthropocene, and one of only two stalagmite records where the S peak has been measured at high resolution.

Climatic and cave settings influence on drip water fluorescent organic matter with implications for fluorescent laminations in stalagmites

“…We favor explanations related to growth phases as important factors for the generation of annual to sub-annual fluorescent laminae, based on their relevance for also explaining cyclicity in colloidally transported trace elements. This concept also would be consistent with observations from Ernesto Cave speleothems, in which periods of condensed growth coincide with a higher overall fluorescence (Borsato et al, 2023). The process could also provide an explanation for the lack of annual to sub-annual scale fluorescent lamination in some active stalagmites from the cave (such as PG-2, close to the drip site PLA ).…”

“…Highly insoluble transition metals and REE-like elements such as Cu or Y are inferred to be transported in drip waters as complexes with organic ligands such as humic and fulvic acids (Hartland et al, 2014; Hartland and Zitoun, 2018). In stalagmites, seasonal layers of enhanced fluorescence often coincide with elevated concentrations of these elements (Borsato et al, 2023; Sliwinski et al, 2023). However, a comparison of C1 and C5 concentrations with the concentration of drip water Cu (Fig.…”

“…The correlations at MUS and SNO locations, and between SKY and δ 13 C DIC , are not given because fewer than three joint observations between drip water chemistry and the PARAFAC model are available. elevated concentrations of these elements (Borsato et al, 2023;Sliwinski et al, 2023). However, a comparison of C1 and C5 concentrations with the concentration of drip water Cu (Fig.…”

The influence of fluid inclusions, organics, and calcite fabric on trace element distributions in stalagmites

“…We also do not see an ubiquitous covariation of Y and Zn as suggested by Chiarini et al (2017) or Sliwinski and Stoll (2021) and described in many annually banded stalagmites (Borsato et al, 2023, Borsato et al, 2007. The correlation of Y and Zn is clear only in SS1 (Fig.…”

Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series

“…Speleothems, typically stalagmites, provide a potential GSSP location as they show annual lamination and there is precedent with definition of the Meghalayan Stage (Upper Holocene Subseries) in this medium. The Ernesto Cave, Italy illustrates the potential of speleothems (Waters et al, 2018) and Borsato et al (2023) reassess all data for two speleothems from this cave. The site had been occupied by humans until isolated by a landslide ~8.0 ka; following its rediscovery in 1983 CE the site has been accessed only for scientific study, with long-term monitoring of the site.…”