The Sensex at the Bombay Stock Exchange plunged 328 points, or 2 percent, to 16,142, today, on heavy selling by investors, amid a sell-off in the global stock markets, on fears of a worldwide economic slowdown.During the session, the Sensex had slipped below the 16,000 level for the first time in nearly 15 months. The Nifty at the National Stock Exchange dropped 99 points, or 2 percent, to 4,846. Stock markets in Japan, China, Hong Kong, South Korea and Singapore wre hammered down by between 1 percent and 6 percent.