Searching for Travertines, Calcretes and Speleothems in Deep Time: 1 Processes, Appearances, Predictions and the Impact of Plants 2 3 A.T. Brasier 4 5 Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, Scotland, UK. G75 0QF 6 (a.brasier@suerc.gla.ac.uk ; Tel: 0044-1355-270-147; Fax: 0044-1355-229-898 ) 7 8 Abstract 9 Common models for modern calcite precipitation in and around caves, soils, springs and streams 10 involve CO 2 supplied by thick, high pCO 2 biogenic soils which were probably thin or non- 11 existent before vascular plants. Indeed plant-influenced chemical weathering might have caused 12 accelerated terrestrial carbonate production from the Devonian onwards. However terrestrial 13 carbonates have also been documented from the Archaean, Proterozoic, Cambrian, Ordovician 14 and Silurian. Mechanisms which could have caused non-marine carbonates to precipitate without 15 organic-rich soils are described, and some geological events likely to have influenced non- 16 marine carbonate precipitation up to the origin of vascular plants are highlighted. As organisms 17 have evolved, so have the petrographic characteristics of non-marine carbonates; some examples 18 of this are also given here. 19 20 21 Keywords: calcrete, travertine, speleothem, terrestrial vegetation, Palaeozoic, Precambrian 22 23 24 1. Introduction 25 26 Terrestrial carbonates are frequently used in palaeoclimatic and palaeoenvironmental 27 reconstructions (e.g. Andrews, 2006; Andrews and Brasier, 2005; Retallack, 1997; Fairchild et 28 al. 2006). Most of what is currently known about such carbonates, however, has come from the 29 Devonian to Holocene record of soil (e.g. Esteban and Klappa, 1983; Wright and Tucker, 1991; 30 Wright, 2007), spring, stream, lake (e.g. Pedley, 1990; Ford and Pedley, 1996; Jones and Renaut, 31 2010) and cave carbonates (e.g. Fairchild et al. 2006; Frisia and Borsato, 2010), so that pathways 32 leading to terrestrial carbonate lithogenesis have largely been viewed in terms relating to the 33 influence of vascular land plants with roots. Much less is known about the character and 34