Nothing new under the sun.......

Tony holding the "Newall Boulder".  Courtesy Salisbury Museum.

 What with all this interest in smallish bullet-shaped clasts transported subglacially, I have been finding them all over the place!  Above are two photos of clasts found on the shoreline of Blido in washed glacial deposits, and below we see Tony holding the Newall Boulder in Salisbury Museum.  All three are approx the same size and weight.  The Swedish clasts are made of Precambrian gneiss, and the Newall boulder is made (we reckon) of Ordovician welded tuff and lava.  The Swedish clasts are in pristine condition, with no weathering crust; but they are heavily abraded on faces and edges, with multiple facets and with substantial fracture scars at the lee end.  The fracture scars are old --  they have been somewhat smoothed off either subglacially or by running water.   There are no visible striations; this gneiss hardly ever displays them, even on eroded bedrock surfaces.  In contrast, the Newall boulder has been seriously damaged by percussion, grinding and cutting, as we can see from the dark blue faces on the flanks and ends of the clast.  Maybe we should refer to it as a "failed artefact" -- but there is quite enough of the original boulder left for us to get a pretty good handle on what it was like, where it came from,  and how it was shaped by the forces of nature.........