Integrated high-resolution stratigraphy: Deciphering fundamental controls on basin evolution

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Sedimentary rocks provide the most important record of life on Earth, as well as recording the history of the atmosphere and oceans. The proposed programme of investigation is concerned with sedimentary rocks deposited during the Cretaceous Period, between about 108 and 83 million years ago in what is now NE British Columbia, Alberta and Saskatchewan. At that time, the Prairie region was occupied by a shallow sea that at times connected the Arctic Ocean with the Gulf of Mexico. To the west, the actively-rising Rocky Mountain chain was shedding sediment eastward into the Seaway, building deltas and coastal plains that supported a lush flora of both conifers, and, after about 104 million years ago, a rapidly diversifying assemblage of flowering plants. Environments ranging from the sandy sea shore to inland river valleys and floodplains were inhabited by many types of dinosaur, with hadrosaurs, ankylosaurs, and various theropods being particularly common. These animals are known mainly from the abundant footprints that they left in the sediments; - bones are rarely preserved. The Canadian Shield formed a low-lying land area in northern Saskatchewan and Manitoba that shed sediment westward into the seaway. We have discovered that at one time, a huge delta built out from the eastern shore to completely block the seaway. The mass of the rising Rocky Mountains depressed the crust for about 1000 km to the east, allowing a westward-thickening wedge of sediment to accumulate. Because deposition occurred in shallow water and on low-lying coastal plains, even small changes in sea-level caused lateral shifts in the shoreline position as the water alternately deepened and shallowed. Changes in the rate at which the basin subsided also caused major changes in the position of the ancient shoreline. Shoreline movements can be deduced by studying the vertical succession and lateral distribution of terrestrial, shoreline and offshore sediments. By mapping the distribution of these rock types using abundant exploration borehole data, as well as through outcrop study, it is possible to reconstruct how the geography of the basin evolved, and to assess the relative influence of sea-level (mostly controlled by changing climate), and subsidence or uplift (controlled by plate tectonics), on basin geography.***The Cretaceous rocks of Western Canada provide not only a detailed record of evolving animals, plants, sea-level change and mountain-building, but also a wealth of natural resources, of vital interest to Provincial economies. Marine mudstones deposited in the centre of the seaway contain algal tissues that, with heat, pressure, and time, generated natural gas and petroleum that accumulated in the porous sandy shoreline sediments. Low-lying coastal plains accumulated thick peat deposits that later compacted to high-quality coal, that is of major economic significance in towns like Grande Cache and Tumbler Ridge. **