(Reuters) -Union Pacific reported a fourth-quarter profit on Thursday that rose 7% on the back of higher grain and fertilizer shipments and core pricing gains, sending the railroad operator's shares up more than 4% before the bell.

Shares of Union Pacific Corp. rallied 5.20% to $248.05 Thursday, on what proved to be an all-around positive trading session for the stock market, with the S&P 500 Index rising 0.53% to 6,118.71 and the Dow Jones Industrial Average rising 0.

Union Pacific on Thursday posted a better-than-expected profit for the fourth quarter helped by improving volumes and robust pricing, which was partially offset by lower fuel surcharge and less profitable cargo mix.