Open AccessBubble trail and folia in cenote Zapote, Mexico: petrographic evidence for abiotic precipitation driven by CO2 degassing below the water table
Author(s) -
Rafael LópezMartínez,
Fernando Gázquez,
José María Calaforra,
Philippe Audra,
J.Y. Bigot,
Teresa Puig,
Rocı́o Alcántara-Hernández,
Ángel José Sánchez Navarro,
P. Crochet,
Liliana Martinez,
Raquel Daza Brunet
Publication year - 2020
Publication title -
international journal of speleology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.41
H-Index - 32
eISSN - 1827-7713
pISSN - 0392-6672
DOI - 10.5038/1827-806x.49.3.2344
Subject(s) - petrography , calcite , geology , paleontology , cave , carbonate , micrite , speleothem , precipitation , biology , ecology , chemistry , facies , physics , organic chemistry , structural basin , meteorology
Folia are speleothems that resemble bells, inverted cups, or bracket fungi, and whose origins are still controversial. Cenote Zapote (an underwater cave) in the Yucatán Peninsula (México), is home to some of the largest folia reported to date. These speleothems are currently growing in an active underwater system, meaning this site offers an excellent opportunity to constrain the different formation models proposed for folia, which have traditionally relied on inactive examples. In Cenote Zapote, folia are closely related to bubble trails and cupolas, suggesting an underwater CO2-degassing process. In thin section, they display a succession of columnar-open and columnar-elongated endings in micrite-dendritic fabrics. Our petrographic and geochemical results demonstrate the abiotic origin of these folia and indicate carbonate precipitation from cold water by CO2 degassing below the water table that started at least 5,210 yrs BP. We conclude that these folia formed as a result of subaqueous calcite precipitation around CO2 bubbles trapped below overhanging walls of the cave. The sequential alternation of columnar and micritic fabrics can be explained by changes in the position of the halocline and H2S-rich water mass while the exceptional size is the result of carbonate precipitation from waters saturated in CaCO3 during thousans of years. Then we propose the classification of these speleothems as a subtype of folia. This subtype could be named Hells Bells, respecting its original description.