The ichnology of the fluvial-tidal transition: Interplay of ecologic and evolutionary controls

摘要

8.1 INTRODUCTION Our knowledge of the ichnology of marginal-marine depositional systems, such as estuaries and deltas, has increased significantly with the recognition of the role that stress factors play in controlling the distribution of benthic faunas and their associated biogenic structures (e.g., Buatois and Mángano, 2011a; Buatois et al., 1997; Gingras et al, 2012; MacEachern and Gingras, 2007; MacEachern and Pemberton, 1994; MacEachern et al., 2005; Mángano and Buatois, 2004; McIlroy, 2004; Pemberton et al, 1982). In addition, during the last couple of decades significant progress has been made on the ichnology of freshwater and terrestrial settings (e.g., Buatois and Mángano, 1995, 2004; Genise, 2004; Genise et al., 2000, 2004, 2010; Melchor et al., 2012; Scott et al., 2012). In spite of this, characterization of the ichnofaunas in the continental-marine transition has definitely lagged behind in part because continental and marginal-marine ichnofaunas tend to occur separately and are treated as such in most studies. However, there is a growing number of studies documenting examples of biogenic structures in the fluvial to tidal transition in both the fossil record (e.g., Buatois et al., 1997, 1998a; Mángano and Buatois, 2004) and, more recently, in modem settings (e.g., Dashtgard et al., 2012; Johnson and Dashtgard, 2014). Unfortunately, most of the available deltaic and estuarine models have not incorporated the freshwater and terrestrial dataset yet (see Buatois and Mángano, 2011a for an exception). Therefore, it is timely to