Carbonate build-ups in lacustrine, hydrothermal and fluvial settings: comparing depositional geometry, fabric types and geochemical signature

Abstract

Carbonate build-ups in lakes, hydrothermal and fluvial settings are characterized by distinctive geometry, spatial distribution, fabrics and geochemical signature but also by some comparable features. Lake margin bioherms form continuous belts for hundreds of metres to kilometres, subparallel to shorelines. Sublacustrine spring mounds are spaced at hundreds of metres to kilometres and aligned along faults. Hydrothermal travertine mounds and aprons with planar clinoforms or terraced slopes are controlled by faults, thermal water discharge and substrate topography. Fluvial tufa barrages, cascades and terraced slopes are controlled by climate, vegetation and substrate gradient. The wide spectrum of carbonate microfabrics ranges from clotted peloidal micrite and laminated boundstone to crystalline dendrite cementstone. Non-marine carbonate microfabrics cannot be linked to specific depositional environments, and are not deterministic proxies for the interpretation of build-up architecture. Microfabric associations can be indicative, but not exclusive, of specific depositional environments and geometry. Stable isotope geochemistry is a useful tool to distinguish between hydrothermal, karstic freshwater and evaporative lake carbonates. Carbonate precipitation results from a continuum of abiotic and biologically influenced/induced processes in settings where carbonate supersaturation is largely driven by physico-chemical mechanisms and microbial biofilms, even if acting as passive low-energy surface sites for nucleation, are widely present.

Comparative study of the Pleistocene Cakmak quarry (Denizli Basin, Turkey) and modern Mammoth Hot Springs deposits (Yellowstone National Park, USA)

“…10A). The crust fabric is one of the most ubiquitous fabrics in spring carbonate deposits and different terms have been used to depict and classify them (Chafetz and Folk, 1984;Turner and Jones, 2005;Gandin and Capezzuoli, 2014;Della Porta, 2015), including the 'crystalline dendrite, dendrite crust and micritic dendrite lithotypes described at Faber and Ece quarries . The observed microfabric is generally composed of multiple, elongated to feather-like calcite crystals forming 'dendrites' (Jones and Renaut, 2008) (Fig.…”

“…This might indicate that spring water was substantially cooler during deposition of Facies C2 and possibly during several stages in the evolution of the Cakmak spring system. Henceforth, two Proximal Slope Facies are recognized, a crystalline Proximal Slope (C1), characteristic of MHS, Cakmak and many other travertine systems (Okumura et al, 2012;Gandin and Capezzuoli, 2014;Della Porta, 2015) and a phyto Proximal Slope (C2) Facies.…”

“…The contacts between those units can be gradational, but are most often abrupt and sharp. When looking at active vents at MHS, the surface flow, upon emergence, is topographically controlled (Pentecost, 2005;Della Porta, 2015). When the spring water supply at the vent increases or decreases, the water chemistry and temperature will shift and as such CaCO 3 fabrics and facies will move laterally (Pentecost, 2005).…”

“…Different travertine depositional facies models of modern spring systems have been proposed to describe the complex textural and geometric variations of ancient spring deposits (Guo and Riding, 1998;Fouke et al, 2000;Capezzuoli et al, 2014;Claes et al, 2015;Della Porta, 2015) and to accurately reconstruct the environmental conditions under which ancient deposits originally formed and evolved (Chafetz and Folk, 1984;Veysey et al, 2008;Fouke, 2011;Gandin and Capezzuoli, 2014;Sotohian and Ranjbaran, 2015). A facies, as summarized by James and Dalrymple (2010), is a 'body of (sedimentary) rock characterized by a particular combination of lithology and physical and biological structures that bestow an aspect that is different from the bodies of rock adjacent.…”

“…Despite different reviews about continental carbonate spring facies and fabrics (Guo and Riding, 1998;Chafetz and Guidry, 2003;Pentecost, 2005;De Filippis et al, 2012;Capezzuoli et al, 2014;Della Porta, 2015), some of the most extensive sites of modern and ancient travertine deposition have never been compared. Hence, an integrated and comparative travertine depositional facies model based on spatial and quantitative mapping (at meter to kilometer length scales) of different, key travertine systems does not exist.…”