Puddingstones: Plum Wonderful Stones filled with "Berries & Currants" of Jasper & other Pebbles
For some reason, all sorts of stones have been on my mind the past few weeks, including the wonderful Michigan puddingstones pictured above. Their name comes from the resemblance to English suet or pudding filled with berries and currants, and, well, they do look good enough to eat!
Puddingstone, or plum-pudding stone, is the name given to conglomerates (of different origins, compositions, and locations) that consists of distinctly rounded pebbles whose colors (in this case, Jasper chalcedony red) contrast greatly with the color of the finer-grained matrix (or cement) surrounding the pebbles. The Michigan puddingstones pictured above are likely associated with glacial activity of fairly recent origin.
In contrast, I cut my geologic teeth in the Northampton and Boston, Massachusetts, area where we drove miles and miles from little scraps of outcrops to other little scraps of outcrops to look at the Roxsbury Conglomerate of the Boston Basin:
Originally thought to be associated with shallow river and lake basins, the prevailing hypothesis is that these puddingstones or conglomerates are associated with very deep marine basins in a suite of rocks known as turbidites, associated with deep-sea submarine fans. They are also much, much older (and they look it!), dating from 570 to 595 million years ago.
There are other puddingstones, such as the Hertfordshire Conglomerate in merry old England :
And the Jelly Bean Conglomerate of Arizona and the western United States:
I had the good fortune of attending geologic field camp in Arizona where we could see the Jelly Bean comglomerate stretching out for long distances (no driving needed, it was strictly a walk in the geologic park).
Naming stones or rock formations based on their similarities to foods we eat is decidedly more fun than the geologic convention of naming formations based on the locale where they were first discovered. It is a sense of whimsy I shared with Robert W. Hickman, my first geologist boss, amazing teacher, and good friend. I am also writing Bob's eulogy today. Bob would have enjoyed this:
Word Woman (aka Scientific Steph)