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THE CONTINENTAL REALM 269

THE CONTINENTAL REALM 269

e the matrix of lithified :s to produce a tracę ? organism behaviors oii, wood, bonę, and interactions are con-•. ochemical factors and miąue to Continental <own, 1992; Hasiotis, p between organism r. media characteristics,

0-5 ppt (e.g., Ward, 1992), including rivers and lakes, but excludes hypersaline and saline-alkaline waters that are found commonly on the continent; it also ignores life on land. These terms, however, do have an appropriate place in Continental ichnology as descrip-tors of environments that are predominantly above the water table (i.e., terrestrial) and environments where the water table is above the land surface most of the ime (i.e., aąuatic).

The best approach to determine what factors and processes likely control the diversity, abundance, and distribution of Continental tracę fossils is to study the relationship of modem trace-making terrestrial and aąuatic biota with the habitats and environments in which they live (e.g., Chamberlain, 1975; Voorhies, 1975; Hasiotis and Bown, 1992; Hasiotis, 2002). Continental environments contain a great diversity of above- and below-ground trace-making organisms (e.g., Wallwork, 1970; Whittaker, 1975; Wilson, 1992). These organisms are directly and indirectly related to sediment, soils, and other media through feeding, dwelling, locomotion, reproduction, escaping, and searching behavior evident as tracks, trails, burrows, nests, and borings of animals and root pattems of plants in terrestrial and aąuatic environments. Borings differ from burrows in that an organism has to mechanically cut into or ren sedimentary or crystalline (eg., Ekdale et al., 1984). and media (i.e., sedimer lithified and crystalline • trolled by biological and p processes characteristic o environments (Hasiotis 2000). Only after the relai behariors, burrow morpho'.

biological and physicochemical factors, and environ-mental processes are identified and understood, can tracę fossils be used morę accurately to interpret Continental deposits (Hasiotis, 2002, 2004).

Although studies of Continental tracę fossils have increased markedly during the last few decades, most approaches are still founded on concepts and principia developed for marinę organism behavior and ichnology, including the use of ichnofacies (e.g., Buatois et al., 1998; Genise et al., 2000; Miller et al., 2002; Buatois and Mangano, 2004; Genise et al., 2004). As an artifact of this approach, Continental trace-fossil studies have yielded interpretations and associations between ichnofossils and behavior, paleosols, and organism evolution that do not accurately reflect processes that operated in Continental systems or that controlled organism behavior and its distribution.

The solution to this problem is to link trace-making behavior and organism-media interactions (i.e., neoichnology) in modem Continental environments to associations and pattems between ichnofossils and sedimentary fabrics (i.e., palaeoichnology). Such linkages should provide morę accurate interpretations of the processes and factors that influenced organism behavior and its distribution in deep geologie time (e.g., Chamberlain, 1975; Hole, 1981; Smith, 1986; Hasiotis and Mitchell, 1993; Villani et al., 1999; Vittum et al., 1999; Brake et al., 2002; Hasiotis, 2002, 2003, 2004; Hembree and Hasiotis, 2006; Kraus and Hasiotis, 2006). A similar strategy was used by German scientists at Senckenberg Institute in Wilhelmshaven during several decades of study of North Sea tidalflats to link the significance of biogenic structures and modern sediments to the preservation of tracę fossils in ancient strata (e.g., Richter, 1920; Hantzschel, 1935,1975; Reineck, 1955,1958; Hertweck and Reineck, 1966; Schafer, 1972).

THE CONTINENTAL REALM

In order to understand and interpret better the behavior and significance of Continental ichnofossils, sedimentary environments and their biological and physicochemical attributes should be properly char-acterized in an integrated context. Ancient sedimentary environments are understood best by evaluating modern Continental depositional settings and the factors and processes that control the distribution of trace-making organisms.

The depositional settings of the Continental realm represent a mosaic of landscapes with high spatial and temporal heterogeneity of water, soil develop-ment, and environmental stability (e.g., Wallwork, 1970; Whittaker, 1975; Aber and Melillo, 1991). Continental landscapes produced by heterogeneity contain a hierarchy of organisms as populations, communities, ecosystems, and biomes, all of which are influenced strongly by environment, topography, ecology, hydrology, and climate (Whittaker, 1975; Aber and Melillo, 1991; Jones and Lawton, 1995). The vertical and lateral distributions of trace-making biota within a sedimentary environment are also influenced in the same manner.

Spatial Variability of Water: Terrestrial, Aąuatic, and Periaąuatic Settings

The Continental realm (Fig. 16.1) is dominated by alluvial (fltivial and overbank), lacustrine, palustrine,