Sedimentology and geochemistry of a human‐induced tufa deposit: Implications for palaeoclimatic research

Abstract

Geochemical variations across laminated tufas and travertines may reflect the growth style of the carbonate build-up and not just climate-related changes. This work presents the study of a carbonate deposit, formed on a ravine wall in Gran Canaria Island (Spain), from a broken pipe system used for irrigation of banana plantations. The deposit is a few tens of metres long and has a stepped morphology formed by successive cascade-barriers and pools. The main facies are framestones of coated stems, laminated bindstones, phytoclastic wackestones and silty mudstones, all of which display micritic or coarse crystalline textures. Lamination from a framestone with coarse crystalline texture was studied from a petrological-sedimentological and geochemical perspective, and water palaeotemperatures were calculated. Lamination displaying five orders of magnitude, from daily to annual or higher, was controlled by the discontinuous supply of water. Lamination consists of crystalline laminae-discontinuity couplets at all observed scales. Estimated mean precipitation rates are 0Á7 mm year À1 , but discontinuity of sedimentation at all lamination orders may have involved greater precipitation rates. Whereas elemental geochemistry suggests variable conditions not far from chemical equilibrium, stable isotopes suggest that calcite precipitated under disequilibrium conditions. However, the small dimensions of the deposit and the relatively high flow velocities allowed lack of d 13 C and d 18 O isotope fractionation in CO 2 -HCO À 3 nor in HCO À 3 -calcite, leading to independent temperature calculations, both with mean values of 25°C. Isotopic trends found throughout lamination cannot be explained by strong changes in water temperature nor in d 13 C DIC or d 18 O w . The correction made to eliminate these isotopic trends yielded narrower temperature ranges. This paper discusses the accuracy of temperature estimations despite the difficulties coming from disequilibrium and how isotopic trends through time could be explained by the growth of the deposit and not by climate-related changes.

A multi‐scale approach to laminated microbial deposits in non‐marine carbonate environments through examples of the Cenozoic, north‐east Iberian Peninsula, Spain

“…Moreover, trace element composition of successive laminae can also show a rhythmic or trending pattern, which is usually parallel to textural changes. Rodríguez‐Berriguete et al (2018) established different orders of lamination in a recent laminated deposit based on high‐resolution geochemical variations, which were consistent with changes in daily to annual water availability.…”

The fate of a travertine record: Impact of early diagenesis on the Y‐10 core (Mammoth Hot Springs, Yellowstone National Park, USA)

“…Such rates are inferior to those measured in the active Mammoth springs by precipitation experiments, which are on the order of 0.2–1.0 mg/cm 3 h or ≤5 mm/day (Fouke, 2011; Kandianis et al, 2008). They are, however, higher than values found for banded travertine in fissure ridges at Futamata (0.06 mm/year; Shiraishi et al, 2020) and at different locations in Turkey (Altunel & Karabacak, 2005; Mesci et al, 2008) or for tufa deposits in Spain (average 0.7 mm/year; Rodríguez‐Berriguete et al, 2018). In situ measurements at Mammoth were taken over a couple of days in an active stream.…”

“…The deposition of (mostly) calcium carbonates results from the interplay of physicochemical processes (CO 2 degassing, flow turbulence) and the presence (nucleation templates) and activity of (sulphate reducing, photosynthetic; micro)biota (Andrews & Brasier, 2005; Bissett et al, 2008; Pentecost, 2005; Takashima & Kano, 2008). Studying spring carbonate depositional processes will help us understand the preservation and/or alteration of these typically laminated, potential palaeo‐environmental and palaeoclimate records (Andrews & Brasier, 2005; Brasier et al, 2010; Kano et al, 2003; Rodríguez‐Berriguete et al, 2018). Furthermore, the high rates of carbonate precipitation (0.2–1.0 mg/cm 3 h at MHS, Fouke, 2011) makes the study of carbonate depositional processes in these settings relevant for different engineering and geotechnical applications (clogging of filters and wells in (geo)thermal installations, CO 2 storage; Boch et al, 2017; Zhang et al, 2018).…”

Coupling textural and stable-isotope variations in fluvial stromatolites: Comparison of Pleistocene and recent records in NE Spain

“…Texture provides information on the sedimentation context of the tufa formation. Particularly, in tufa stromatolites, the lamination allows annual resolution of the environmental signature (Kano et al 2007;Arenas and Jones 2017;Rodríguez-Berriguete et al 2018). In addition, stable isotopes can provide significant information about climate parameters on different time scales and, at times, even quantitative variations of seasonal temperature, via the 18 O/ 16 O fractionation.…”

“…As for the δ 13 C calcite , it reflects, among other parameters, the relative contribution of organic carbon, which can depend on biota development and water availability (Andrews 2006). Nevertheless, the diversity of factors that are involved in the tufa isotopic signature makes it difficult to extract palaeoenvironmental information from fossil tufa (Lojen et al 2004;Anzalone et al 2007;Rodríguez-Berriguete et al 2018).…”