Murray K. Gingras¹, S. George Pemberton², Edward Clifton³, Stephen M. Hubbard⁴, Jason M. Lavigne⁵, Michael J. Ranger⁶, Matti Räsänen⁷, Tom Saunders⁸, John-Paul Zonneveld⁹

(1) University of New Brunswick, Fredricton, NB
(2) University of Alberta, Edmonton, AB
(3) U.S. Geological Survey, Los Altos, CA
(4) Shell Canada Limited, Calgary, AB
(5) Talisman Energy, Calgary, AB
(6) M.J. Ranger Consulting Ltd, Chestermere, AB
(7) University of Turku, Turku, Finland
(8) University of Alberta, Edmonton, Canada, Edmonton, AB
(9) University of Calgary, Calgary, AB

ABSTRACT: Sedimentology and Ichnology: an Evolving Synergy

Despite notable progress in the last two decades, it is still a considerable challenge to identify brackish-water, tidally-influenced deposits in the rock record. This is true of outcrop and core-based data sets. In fact, the general lack of recognition that there are few unique tidal and brackish indicators has hampered our effort to recognize marginal marine and particularly estuarine deposits. Of all the tools at a sedimentary geologist's disposal, none are more informative nor can be applied so readily as sedimentology and ichnology. Over the last two decades the synergy between these two disciplines has grown appreciably and together they are now a foundation of any core or outcrop study. This paper explores the relationship between traditional sedimentology and ichnology. It also illustrates the utility of applying this relationship to the rock record to (1) elucidate the nature of observed rythmicity; (2) divulge the degree of marine incursion into an area; (3) assess the degree of salinity stress in the rock record: and, (4) reveal the tidal range and degree of tidal dominance of an estuarine deposit. Several case studies are discussed and considered in light of modern data gathered from Willapa Bay, Washington. These case studies include core and outcrop from the Cretaceous Bluesky, McMurray, and Horseshoe Canyon Formations in Alberta, and various Triassic strata in northeastern British Columbia. Finally, these data are applied analogously to outcroppings of the Peruvian Pebas Formation (Miocene) that detail a history of marine incursion into continental South America.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado