The Dow Jones Industrial Average sank nearly 1,200 points Thursday, deepening a weeklong global market rout caused by worries that the coronavirus outbreak will wreak havoc on the global economy.The S&P 500 has now plunged 12% from the all-time high it set just a week ago. That puts the index in what market watchers call a “correction,” which analysts have said was long overdue in this bull market, which is the longest in history.It was the worst one-day drop for the market since 2011, and stocks are now headed for their worst week since October 2008, during the global financial crisis.The losses extended a slide in stocks that has wiped out the solid gains major indexes posted early this year.