Spring Creek Group, a five-year-old social media marketing agency, was sold today to the giant Interpublic Group.

Terms of the deal weren't disclosed but Spring Creek's 35 employees, including founding partner Clay McDaniel, will remain based in Pioneer Square.

The agency will also keep its name and operate within Interpublic's "Mediabrands Audience Platform."

Spring Creek was started in 2006 and has blue chip clients, including Microsoft, HTC, Best Buy and U.S. Bank.

It describes itself as a "social marketing agency that helps organizations of all sizes increase awareness, build relationships, and drive growth through online engagement."

Combined with Monday's announcement by Seattle agency Banyan Branch -- that it raised $1.7 million for expansion -- Spring Creek's sale emphasizes the concentration of social marketing firms in the area. That's the take of Leigh Fatzinger, chief executive of Nology Media, another firm in the cluster.

"These two deals validate Seattle as a hub for amazing social media talent," Fatzinger said in a press release.