*MacRae, R. Andrew and Hills, L.V., Department of Geology and Geophysics, University of Calgary, Calgary, Alberta, T2N 1N4;

Muecke, G.K., Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 3J5.

Limbicysta is an unusual acritarch (algal cyst) genus recently described from Cretaceous sediments of Australia. This study has discovered two related species in Upper Albian sediments of the Bastion Ridge and Strand Fiord formations of the Sverdrup Basin, Canadian Arctic Islands. The large size (100 microns plus) and distinctive morphology of Limbicysta makes it easy to recognize in palynological samples, yet this is the first report of the genus outside the type area. One species has the typical branching, asymmetric "foot-shaped" process tips of the type species, Limbicysta pediformis Marshall, but has 8 asymmetric processes in an octagonal geometry versus the 5 with one symmetric process in a planar geometry of L. pediformis. The other species has 4 "antler-shaped" symmetric processes in a planar geometry, and is again distinguished from L. pediformis by the number and type of processes. Both species are distinguished from other species of Limbicysta by their single wall layer and lack of longitudinal folds. Some specimens display a polar (antapical?) boss similar to other species, and there is no evidence of an aperture in the cyst wall.

Limbicysta occurs commonly in the upper part of the Bastion Ridge and Strand Fiord formations, in association with a low diversity dinoflagellate assemblage dominated by the dinoflagellate Nyktericysta, large numbers of terrestrial palynomorphs (>90%), and rare Pediastrum and Botryococcus ("freshwater" alga). This assemblage is interpreted as brackish water marine and/or possibly freshwater ± similar to the paleoenvironment interpreted for the Australian occurrence of Limbicysta. Sedimentology and volcanology of the Bastion Ridge and Strand Fiord formations also supports this conclusion. Limbicysta is, therefore, an easily recognized indicator of brackish and/or freshwater paleoenvironments when it occurs in large numbers. The rarity of reports of Limbicysta from other locations probably reflects its paleoecologically restricted distribution.