Abstract
Research on weathered crusts on carbonate rock is essential for paleoenvironmental studies in karst areas. Terra rossa, widely distributed in tropical karst areas, has not been studied in terms of its material sources and geochemistry. Two typical terra rossa profiles on dolomite (SC profile located at Sang Cai, Hoa Binh province) and limestone (TG profile located at Tong Gia, Lao Cai province) in Northern Vietnam were selected to examine the geochemical characteristics and the evolutionary processes of rare earth elements (REEs). Chondrite and bedrock normalized patterns indicated that these two profiles are in situ weathering crusts, meaning they are the residual material remaining after chemical weathering of the lower carbonate rocks. The average value of total REE in the SC profile is 381.19 ppm, which is 30 times higher than the bedrock. In the TG profile, the value is 386.26 ppm, 13 times higher than the bedrock. Compared with the profiles in nearby subtropical areas in Southeast China, the REE enrichment coefficients of terra rossa in Northern Vietnam are much higher. The REE depletion was also different between the SC and TG profiles. The light and heavy REE fractionations in the SC profile are higher than in the TG profile. Paleoclimate inversion analysis shows that the SC profile experienced a stable oxidation condition, whereas the TG profile was subjected to several reducing environments since a weathering crust formed.
Highlights
IntroductionTerra rossa (lateritic weathering crusts) surfaces on carbonate rocks occupy an important position in karst environmental systems research [1]
Terra rossa surfaces on carbonate rocks occupy an important position in karst environmental systems research [1]
Showing strong effects of geochemistry and pedogenesis, the karst geology, geomorphology, and lateritic weathering crusts were formed as unique geological bodies compared with non-karst regions [7]
Summary
Terra rossa (lateritic weathering crusts) surfaces on carbonate rocks occupy an important position in karst environmental systems research [1]. These weathering crusts are regarded as an area of geochemical sensitivity and ecological vulnerability [2]. After multi-stage development, terra rossa recorded information about paleoenvironment and paleoclimatic changes [8,9] This information is vital for paleoclimate analysis, especially in the karst regions that lack Cenozoic sediments [10,11]. In Southeast Asia, extensive amounts of lateritic weathering crusts overlaying carbonate rocks formed an intact area of terra rossa distribution within the tropical–subtropical monsoon climatic zones. Some studies focused mostly on subtropical [12,13,14] and Mediterranean regions [15,16,17]; few focused on the tropical karst areas
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
