Stromatolite Growth in Lagoa Vermelha, Southeastern Coast of Brazil: Evidence of Environmental Changes

• DOI: 10.1017/rdc.2017.126
• Publication Date: 2017-11-28T23:33:26Z
• Authors: Carla Carvalho; Maria Isabela N. ...; Kita Macario; Renato B. Guimarães; Carolina N Keim; Elisamara Sabadin...; Mirian A C Crapez
• Keywords: Stromatolite; Lithification; Tufa; Supralittoral zone

Abstract Among the oldest remains of living beings to have inhabited Earth’s surface, there are stromatolites—laminated sedimentary rocks associated with lithified mats layered phototrophic microbial communities—which grow in specific environmental conditions. In present work, we study a recent carbonatic stromatolite from Lagoa Vermelha (Rio de Janeiro, Brazil), shallow coastal hypersaline lagoon. X-ray diffraction was depth chronological model defining three different sections based on changes mineral composition increased dolomite content. Although mean growth rate 0.19±0.03 mm/yr is observed, discloses decreasing rates among sections. Since formation can be related high availability Mg +2 , confirmed by an expressive presence (Ca, Mg)CO 3 lower were more arid environment, until approximately 1440 cal AD, higher temperatures and consequently promoting water evaporation salinity enhancement.