WASHINGTON — President Obama picked native Oklahoman Beth Garrett for a top post at the U.S. Department of Treasury.In the early 1990s, Garrett served on the staff of then-U.S. Sen. David Boren. She was Boren’s legal counsel and legislative assistant for tax, budget and welfare reform issues.According to the White House announcement dated Saturday, the president intends to nominate Garrett to be assistant secretary for tax policy.