Terrestrial burrows represent low sea level events within the marine sediments of the Cretaceous Cardium Formation, Alberta
Detailed core study of the Cardium Formation in west-central Alberta showed that terrestrial trace fossil (Taenidium) is present on a possible sequence boundary after a rapid sea level drop on a 4th- 5th order scale. The Cardium Formation represents the Western Interior Seaway during the Late Cretaceous, and provides evidence of several sea level fluctuations. Four wells were studied and total of 40m of core was logged from these wells. These cores demonstrated that terrestrial traces occurred above the regressive surface of erosion, during a period of relative sea level fall. A distinct pattern of mudstone being abruptly overlain by coarser sandstone was seen in the studied cores. The terrestrial trace (Taenidium) was found in the coarser and sandier marine sediments of the selected cores. The majority of the cored intervals contain marine traces including Zoophycos, so the presence of a terrestrial burrows suggests landward movement of the shoreline at that time. This example of terrestrial traces in the Cardium Formation helps to demonstrate that terrestrial traces can be used to help interpret sea level fluctuations in the rock record.
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