Michigan Puddingstone

Steven Wade Veatch USA) Michigan’s puddingstones are intriguing rocks that look like a glob of pudding stuffed with raisins, nuts and bits of cranberries. These white rocks with small red, brown, purple and black pebbles are not a Michigan product. During the last ice age, they hitched a ride into Michigan on an ice sheet and got off in the southern part of the state when the ice melted. Puddingstones went through several steps in their formation (in what is now part of Ontario, Canada) before they went on their journey to Michigan. First, a network of rapidly flowing streams tumbled red and coffee-brown jasper, funeral-black chert, hematite and quartz in their churning water. Next, the streams deposited the material as sedimentary fill in eroded troughs and as alluvial fans when the streams reduced their velocity, and scattered the colorful pebbles onto mounds of sand (Lowey, 1985; Baumann et al, 2001). Fig. 1. An unpolished puddingstone from Michigan. Some contain trace amounts of gold and diamonds. These rocks are commonly found just after farmers plough their fields in Michigan.  Puddingstones were brought to Michigan by ice age glaciers. (Jo Beckwith specimen. Steven Veatch photograph.) Then, the sand and pebbles hardened beneath the Earth’s surface and, over time, formed sedimentary rocks known as conglomerates (Slawson, 1933). Later, intense heat and pressure metamorphosed the matrix of sand into a light-coloured, coarse-grained, sugary-textured quartzite that tightly held the pebbles (Schaetzl, n.d.). These geological forces formed the puddingstones around 2.3 billion years ago. Today, … Read More

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