Geology is the way - Flute casts are structures produced by currents that scour scoop-shaped marks on the bottom of a basin (e.g. by turbidity currents) These ones are positive marks filled
![Tool marks, trace fossils, and flute casts from the Brallier Formation - Mountain Beltway - AGU Blogosphere Tool marks, trace fossils, and flute casts from the Brallier Formation - Mountain Beltway - AGU Blogosphere](https://blogs.agu.org/mountainbeltway/files/2015/10/IMG_1733.jpg)
Tool marks, trace fossils, and flute casts from the Brallier Formation - Mountain Beltway - AGU Blogosphere
![GC81V1P Paleocurrent Indicators: Flute Casts (Earthcache) in North West England, United Kingdom created by Team Microdot GC81V1P Paleocurrent Indicators: Flute Casts (Earthcache) in North West England, United Kingdom created by Team Microdot](https://img.geocaching.com/cache/large/8f18e5e5-3127-4ba0-9e3f-c54a1f9b71d5.png)
GC81V1P Paleocurrent Indicators: Flute Casts (Earthcache) in North West England, United Kingdom created by Team Microdot
![A: Elongate slightly asymmetrical flute cast on the lower bedding plane... | Download Scientific Diagram A: Elongate slightly asymmetrical flute cast on the lower bedding plane... | Download Scientific Diagram](https://www.researchgate.net/profile/Jozef-Hok/publication/318277795/figure/fig9/AS:526056174358528@1502432973090/A-Elongate-slightly-asymmetrical-flute-cast-on-the-lower-bedding-plane-of-a-sandstone.png)