Bann, Kerrie L.1, Murray K. Gingras2, James A. MacEachern3
(1) University of Alberta, Edmonton, AB
(2) Ichnology Research Group, Department of Earth and Atmospheric Sciences, University of
Alberta, Edmonton, AB
(3) Simon Fraser University, Burnaby, BC
ABSTRACT: Changes in Latitude, Changes in Attitude: Two Outstanding Modern Occurrences of the Teredolites Ichnofacies
Teredolites ichnocoenoses are examined from the modern temperate bay-margin of
Willapa Bay, Washington, USA and subtropical Moreton Bay of Queensland, Australia. In
particular, in situ log-grounds from the upper intertidal zones are considered.
The woodground suites are imprinted on in situ roots, broken stumps, and strewn
logs. Enclosing substrates variably comprise muds through muddy sands, and contain
abundant organic detritus deposited in supratidal marshes. Tidal and wave processes have
operated to truncate the swamps, exposing in situ tree-root networks and the lowermost
supratidal sediments.
At Willapa Bay, the intertidally exposed stumps and logs support a diverse community of
animals and plants. Boring organisms, encrusters and refugium seekers are found on and
within the xylic substrates, producing traces that are comparable to ichnofossils reported
by paleoichnologists. The wood-boring traces at Willapa Bay are morphologically similar to
the ichnogenera Caulostrepsis, Entobia, Meandropolydora, Psilonichnus,
Rogerella, Teredolites, Thalassinoides and Trypanites.
The Australian subtropical occurrences display borers and refugium seekers, but virtually
no encrusters, forming structures attributable to Teredolites and Thalassinoides.
The stratigraphic significance of these modern locales is consistent with previous modern
and ancient studies that associate the Teredolites ichnofacies with base-level
rise in marginal marine environments, particularly if the xylic materials are more or less
in situ. Thus, the Teredolites ichnofacies is more synonymous with the Glossifungites
ichnofacies than previously considered. In fact, bored xylic media locally form a coeval
surface with adjacent, burrowed firmgrounds and softgrounds. Such modern studies permit
the stratigraphic utility of substrate-controlled ichnofacies to be broadened and better
understood.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.