24 July 2012
Yesterday I showed you salt casts; today I’ll share a different kind of cast: the infillings of small scorings in the sediment made by tumbling pebbles or sticks or other “tools,”tumbling down a current. These small gouges were later infilled from above by a younger deposit of sediment (frequently coarser in grain size). You’re looking at the bottom of a bed here:
These are strata of the Sulphur Mountain Formation, part of the Triassic Spray River Group in Banff National Park. The outcrop is next to the parking lot for Bow Falls in the Banff townsite, where the Bow River cuts through Rundle Mountain to make Tunnel Mountain.
These are the best tool marks I’ve seen in a long time. They reminded me of the excellent flute casts I saw in 2008 on the Pennsylvania Turnpike.