|
| << vorige | volgende >> |
Tijdschrift beschrijving
Alle jaargangen van het bijbehorende tijdschrift
Alle afleveringen van het bijbehorende jaargang
Alle artikelen van de bijbehorende aflevering
Details van artikel 18 van 46 gevonden artikelen
| Titel: |
Ichnofabrics, ichnocoenoses, and ichnofacies implications of an upper cretaceous tidal-inlet sequence (Eutaw formation, central Alabama) |
| Auteur: |
Savrda, Charles E. Locklair, Robert E. Hall, Jessica K. Sadler, Malcolm T. Smith, Michael W. Warren, Jeffrey D. |
| Verschenen in: |
Ichnos |
| Paginering: | Jaargang 6 (1998) nr. 1-2 pagina's 53-74 |
| Jaar: |
1998-10 |
| Inhoud: |
A siliciclastic tidal-inlet sequence within the Tombigbee Sand Member of the Upper Cretaceous Eutaw Formation, central Alabama, is composed of two subfacies distinguished primarily on the basis of form, scale, and orientation of cross-stratification. These subfacies record spatial and temporal variations in net-sedimentation rate, frequency of reworking, and relative importance of slack-water stages, most of which were governed by variations in tidal-current asymmetries and associated hydrodynamic regimes. The dominant ichnocoenosis in both subfacies is characterized by, in general order of decreasing abundance: (1) Macaronichnus, produced by vagile, deep deposit-feeding polychaetes; (2) Conichnus, produced as temporary dwellings or during equilibrium/ escape movements of anemone-like animals; (3) a branched form of Skolithos, attributed to deposit-feeding worms; and (4) Dactyloidites, a subsurface feeding structure made by worms or worm-like organisms. Relative abundances of these ichnotaxa, and degree of bioturbation in general, vary within and between subfacies, in a manner consistent with variations in reworking and net-sedimentation rates. Ophiomorpha defines a subordinate ichnocoenosis that developed only during relatively rare, extended slack-water periods associated with subfacies 2. Assignment of the dominant ichnocoenosis to the Skolithos ichnofacies, which usually typifies high-energy nearshore sands, is inappropriate. Bioturbation by sessile suspension-feeders was apparently limited or precluded altogether by persistently high energy and sedimentations rates, and, consequently, by narrow colonization windows. Instead, the tidal-inlet ichnocoenosis of the Eutaw, and analogous ichnocoenoses in comparable deposits, may be more appropriately assigned to the ill-defined Curvolithus ichnofacies or, alternatively, to a new environmentally restricted ichnofacies. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 18 van 46 gevonden artikelen
| << vorige | volgende >> |