“…Mozley, 1989; Hart, Longstaffe & Plint, 1992; Browne & Kingston, 1993; Baker, Kassan & Hamilton, 1996; Mortimer, Coleman & Rae, 1997; Köhler et al 2013; Rodrigues et al 2015). Their presence in any environment may be indicative of reducing/anoxic conditions (Huber, 1958; Bahrig, 1989; Browne & Kingston, 1993; Mirza, Mohialdeen & Awadh, 2016; Franchi et al 2017; Isaack et al 2017) while they also provide useful information about palaeo-salinity (Garrels, 1960; James, 1966; Curtis & Spears, 1968; Bahrig, 1989; Cundy, Hopkinson & Whitby, 2008; Loope et al 2012).…”