New Geology Maps for SW Oregon, June 11

New maps by the Oregon Department of Geology and Mineral Industries (DOGAMI) reveal more than ever before about the complex and intriguing geology of the southern Oregon coast between Port Orford and Bandon.  Geologists identified thousands of blocks of rock, unalike except for their location, brought together over millions of years by plate tectonics.  “The rocks have their own initial history,” says DOGAMI geologist Tom Wiley. “Then they come together and have a shared history.”  That history becomes even clearer with the emerging technology of zircon dating, which was used for the first time. Geologists collected sandstone for all the area’s geologic units. The sandstone was crushed and the zircon grains collected, then analyzed with a laser. With the potential for more accurate age dating comes a chance to know even more.  “We’re starting to be able to unravel the really complex stories of these far-travelled pieces,” says DOGAMI geologist Jason McClaughry.  The maps also offer much-improved information about geologic hazards and resources. Coastal Curry and Coos counties were last mapped in the 1970s, says McClaughry. Since then, understanding of geologic hazards – such as a Cascadia Subduction Zone earthquake, tsunami, and landslides – has improved, as has mapping technology.  New maps were created with lidar, which provides accurate high-resolution images of the earth. Lidar has dramatically increased identification of potential hazards.  “Early maps showed a handful of landslides,” McClaughry says. “The new map shows 1,400.”  This geologic mapping is part of a multi-year project, begun in 2012, to map the Oregon coast from the California border north to Coos Bay. The effort is supported in part by the U.S. Geological Survey (USGS) STATEMAP component of the National Cooperative Geologic Mapping Program.