Saturday, January 14, 2012

Accretionary Wedge #42 - Countertop Geology & Decorative Stone

The latest Accretionary Wedge, the monthly gathering of the geoblogosphere, is being hosted by Ian Saginor at his '' blog and is asking for 'any countertop or decorative stone that has been separated by humans from it's source.'  While thinking about this topic, I immediately thought of the dimension stone seen while walking the streets of St. Paul, Minnesota to locations or events like the Xcel Energy Center, the St. Paul Winter Carnival, Park Square Theatre or even the Minnesota State Capitol building.

The Google Earth image below attempts to give a sense of location or place for some of the dimension stones shown seen in this post.  Downtown St. Paul is located alongside the Mississippi River.

The old West Publishing Building is faced with 3,600 million-year-old Morton Gneiss at street level.  Type locality and quarry location is found alongside the Minnesota River in Morton, Minnesota.  This particular gneiss is sold commercially as dimension stone under the name "Rainbow Gneiss."

The James J. Hill library is constructed of pink marble from the state of Tennessee.  During his lifetime (1838-1916), James J. Hill was the chief executive officer of the Great Northern Railway while the railroad completed a transcontinental line to Seattle, Washington.  The library is also on the National List of Historic Places.

A recent addition to the city is the Hamm Plaza,which was created in 1992 in the center of St. Paul's entertainment district.  The walkway of the plaza is constructed of at least four different Minnesota igneous rocks - granite, gabbro and anorthosite.  The intrusive red and gray granites (radiometric ages between 1,780 and 1,730 million years ago), are quarried near St. Cloud, Minnesota.  The gabbro and anorthosite are common intrusive components of the Duluth Complex of Mid-Continent Rift System (1,100 million years) along Minnesota's North Shore.

The Church of Assumption, the oldest existing church in St. Paul (1874) is also found on the National Register of Historic Places.  The church and rectory are constructed of locally quarried limestone bedrock.  Underlying most of St. Paul is the fossiliferous Ordovician Plateville Limestone and upon close inspection of these buildings, one can see numerous invertebrate fossils.

Like most states in the United States, Minnesota has numerous companies quarrying rock for use as dimension stone.  Some quarry Morton Gneiss in the Minnesota River Valley, granitefrom the St. Cloud area or the intrusive igneous rocks of the Mid-Continent Rift System, other companies quarry limestone or sandstone from other areas of the state.