Friday Field Photo #177: Flute Marks on Base of Turbidite Bed
This week’s photo is from the Cretaceous strata in Patagonia I’ve been working on for several years. I’m heading down there again this coming field season (January-February) and this time taking one of my new graduate students. I’ll only be down there for a bit over a week because of teaching and other obligations, but that’ll be enough to get my student oriented for his nearly two-month-long field season.
The sandstone bed in the photo above has some beautiful flute marks on the base. These elongate sole marks are formed by small-scale scour into the underlying substrate as a sediment-laden turbidity current flows down a marine slope. The sand that was carried in the flow is then deposited into the scours creating a cast. In most cases, these structures flare out in a down-current direction, which gives us paleocurrent direction. My field partner is pointing in the direction of paleoflow. I’m not sure how many flute marks I’ve measured for paleocurrent over the years — it must be in the thousands by now.
Image: my Flickr