About This Item
- Full text of this item is not available.
- Abstract PDFAbstract PDF(no subscription required)
Share This Item
The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
Volume:
Issue:
First Page:
Last Page:
Title:
Author(s):
Article Type:
Abstract:
Estuarine burrow patterns of the modern polychaete Diopatra cuprae relate to tidal currents in arrangements closely resembling trace-fossil assemblages of a Cambrian tidal sand body.
Dwelling tubes of Diopatra on tidal creek point bars in South Carolina reflect local hydrodynamics in four preservable ways: (1) population density is markedly higher on intertidal bar flanks than in channels; (2) burrows are sparse on parts of the bar shielded from ebb currents; (3) in intertidal areas with high population densities, tubes comprise linear rows normal to flow; and (4) tubes in intertidal areas subject to supercritical flow are ringed by asymmetrically ellipsoidal, current-parallel scour pits preferentially oriented in the ebb direction.
Associations of sedimentary textures and structures in Cambrian orthoquartzites of eastern Pennsylvania are analogous to modern upward-fining tidal-channel and point-bar deposits. Channel deposits are characterized by nonburrowed, thick sets of planar-tangential cross-strata with erosional bases and abundant mudclast lags. Intertidal bars display higher population densities and are characterized by thin sets of planar-tabular cross-strata with bipolar orientations, herringbone cross-stratification, and reactivation surfaces. Monocraterion occurs as a Skolithos burrow top, and only in intertidal sequences; these structures are analogous to the scour pits around Diopatra burrows. In plan, the asymmetrical ellipses of Monocraterion burrows are parallel and arranged in rows. These feature allow the measurement of paleocurrent directions from relatively small bedding-plane exposures.
End_of_Article - Last_Page 415------------