The Ichnology of Modern and Pleistocene Brackish-Water Deposits at Willapa Bay, Washington: Variability in Estuarine Settings

Late Quaternary drainage dynamics in northern Brazil based on the study of a large paleochannel from southwestern Marajó Island

“…The highly bioturbated nature of the sands overlying the discontinuity surface, and, particularly, the types of burrows, including Thalassinoides, Ophiomorpha, Diplocraterion, Planolites, and possibly Teichichnus (?) and rare Skolithos, are similar to assemblages recorded in many high energy, shallow marine to marginal-marine environments (Ekdale et al 1984, Wightman et al 1987, Griffis and Suchanek 1991, Pemberton and Wightman 1992, Beynon and Pemberton 1992, Buatois et al 1998, Gingras et al 1999. The fact that these traces continue below the discontinuity surface, where they form an endured horizon having trace fossils characterized by hard walls, is consistent with firm grounds, typical of Glossifungites ichnofacies Frey 1985, MacEachern et al 1992).…”

The Significance of Bioturbated Inclined Heterolithic Stratification in the Southern Part of the Miocene Solimoes Formation, Rio Acre, Amazonia Brazil

“…Prominent among these are tidal settings, in particular on tidally influenced point bars. Since that publication, IHS has been associated increasingly with tidally influenced, marginal marine deposits (Smith, 1989;Ranger and Pemberton, 1992; Räsä nen et al, 1995; Falcon-Lang, 1998; Witzke et al, 1999; Gingras et al, 1999). Although it is widely accepted that IHS is exceedingly common in mesotidal marginal marine settings, the origin of the mud/sand interbeds still generates debate.…”

“…For a broader view, MacEachern et al (1992) provide a detailed ichnological model for Cretaceous shoreface deposits of the Western Canadian Sedimentary Basin. Modern analogues and a detailed analysis of brackish-water fauna are presented in Gingras et al (1999).…”

“…Furthermore, IHS beds deposited in brackish water settings commonly preserve trace fossils, suggesting that in those instances sedimentation rates are not extraordinary. Also, some authors have suggested that marginal marine IHS simply reflect the shifting of the turbidity maximum due to fluctuations of continental discharge (Smith, 1989;Gingras et al, 1999).…”

Microbially Induced Sedimentary Structures--A New Category Within the Classification of Primary Sedimentary Structures--Discussion

“…(3) What interpretations might be drawn from the observation of runzelmarken in the rock record? Although it is outside the scope of this discussion to thoroughly answer these questions, intuitive answers would include: (1) Using the other sedimentological evidence, such as the presence of rills (Reineck and Singh 1980), nature of the bioturbation (Gingras et al 1999;Zonneveld et al 2000), and the overall sedimentary context (Clifton 1982); (2) although Reineck (1969) showed that dampening of muddy sand was enough to make it cohesive if the sediment is sporadically emergent, microbial stabilization may be the cause of all subtidal wrinkle marks; and (3) microbial colonization evidences colonization windows during which bedforms were moribund and thereby is related to sporadic sediment mobilization.…”