Rock Stars of the Ancient World April 17, 2011

Four display cases at the entrance to the Museum's Hall of Evolution highlight four ancient rocks that are among the oldest things on Earth. Acasta Gneiss, Gowganda Tillite, Grypania spiralis, and Banded Iron formation range in age from two to four billion years old. The Earth itself is estimated to be 4.5 billion years old. The exhibit has its beginnings over ten years ago, when former Museum education coordinator Carl Wozniak gave the Museum a specimen of Grypania spiralis that he had collected near Marquette, Michigan. This specimen is a fossil of the oldest known multicellular organism (2 billion years old), featuring filaments of loop-shaped algae that are easily visible to the naked eye. U-M Geological Sciences professor Jamie Gleason helped the Museum obtain a piece of Acasta Gneiss from the Canadian Geological Survey. Acasta Gneiss is the oldest intact rock on Earth, and is just over four billion years old. The piece on display is from northern Canada. With the help of U-M Geological Sciences profesor Steve Kessler, the Museum acquired a specimen of Banded Iron formation from the collections of the U-M Department of Geology, which shows repeated layers of iron oxides laid down almost two billion years ago. The specimen of Gowganda Tillitte is a piece of ancient glacial till from Ontario, northeast of Lake Huron. The tillite formed during an ice age nearly two billion years ago. Fragments of Gowganda Tillite are found in Michigan as a result of a much more recent glaciation that ended about 10,000 years ago.