* Railroads hurt transport sector
* Microsoft, Amazon results help limit Nasdaq losses
* Dow off 1.3 pct, S&P off 1.4 pct, Nasdaq off 0.5 pct (Updates to late afternoon, changes byline)
By Rodrigo Campos
NEW YORK, Oct 23 (Reuters) - U.S. stocks fell on Friday, with the Dow slipping below the 10,000 mark as industrial companies' weak results overshadowed robust earnings from tech heavy-weights.
The energy and materials sectors suffered as a stronger U.S. dollar hit commodity prices, while an analyst's comments on a major railroad stock hurt the transportation sector.
Shares of Burlington Northern Santa Fe Corp, the second-biggest U.S. railroad, slid nearly 7 percent after a broker cut its price target on the stock and helped drive the Dow Jones Transportation Average down 3.5 percent. An index of S&P industrial companies lost 1.7 percent.
The U.S. dollar strengthened after data showed the UK posted its sixth straight quarter of contraction in gross domestic product, the longest stretch on record, and better-than-expected U.S. housing data gave the greenback an extra boost.
A stronger dollar helped to push oil and commodity prices lower, sending shares of companies in the energy and materials sectors down. The S&P materials sector <.GSPM> fell 2.2 percent.
"Any time the dollar shows signs of life, the stock market goes down. There's a flight to safety," said Joe Saluzzi, co-manager of trading at Themis Trading in Chatham, New Jersey.
"The (weak) UK GDP gave strength to the dollar. And when the dollar is up, oil falls."
The Dow Jones industrial average fell 129.61 points, or 1.29 percent, at 9,951.70. The Standard & Poor's 500 Index dropped 15.04 points, or 1.38 percent, to 1,077.87. The Nasdaq Composite Index lost 10.66 points, or 0.49 percent, to 2,154.63.
ROUGH RIDE ON THE RAILROAD
Burlington Northern shares fell 6.9 percent to $78.79 a day after the company reported a 30 percent drop in quarterly profit. The company hauls a variety of commodities such as coal, grain, lumber, construction materials, automobiles and consumer goods.
An analyst at RBC Capital cut his price target on Burlington Northern's stock to $87 from $91, while he kept his rating at "underperform."
Shares of the top U.S. railroad Union Pacific Corp tumbled 6 percent to $57.37.
Oilfield services company Schlumberger Ltd dropped 5.5 percent to $64.86 after it warned that natural gas drilling activity would remain weak until late 2010. Globally, natural gas prices have been too low to justify drilling many new wells, Schlumberger said.
U.S. crude oil futures fell 69 cents, or 0.9 percent, to settle at $80.50 a barrel. The S&P energy sector index slid 2.1 percent.
Top decliners in the tech sector included Broadcom Corp and MEMC Electronic Materials Inc following disappointing quarterly results. Shares of Broadcom, which makes chips for everything from cellphones to TV set-top boxes, slid 6.3 percent to $28.79 on Nasdaq. MEMC Electronic Materials' stock dropped 9.5 percent to $13.96 on the New York Stock Exchange.
A semiconductor index lost 2.9 percent.
But the Nasdaq's losses were limited after major earnings beats from Microsoft Corp and Amazon.com Inc. Microsoft jumped 5.5 percent to $28.05, while Amazon soared 26.6 percent to $118.28, after earlier climbing to a lifetime high of $119.65.
Earlier in the day, September data showed sales of previously owned U.S. homes surged to their highest level since July 2007. (Additional reporting by Aarthi Sivaraman) (Editing by Jan Paschal)