The U.S. dollar surged ahead on international money markets yesterday, and major central banks were in the unusual position of selling dollars to keep it from rising too fast. Gold fell sharply.

A New York dealer said the cut-off of oil supplies from Iran could make a stronger dollar economically hurtful to European nations and Japan, which must find other sources of oil and pay for it in U.S. dollars.

The price of gold fell sharply. In Zurich, it closed at $299.375 an ounce a $4.50 drop from Wednesday's $233.875. In London, gold closed at $229.625, a loss of $2.70 from Wednesday's $232.375.

In Frankfurt, the dollar rose to 1.8845 marks from 1.8644, the highest rate since Dec. 15. In Zurich, it rose to 1.70995 Swiss francs from 1.69575.

In Parts, the dollar jumped to 4.3225 French francs from 4.2735; in Milan to 845.30 Lira from 840.95; in Amsterdam to 2.0320 guilders from 2.0165 and in Brussels to 30.0950 Belgian francs from 29.825.

In London, the pound eased to $1.9810 from $1.99 Wednesday.

The dollar was mixed in New York. It closed at: 29:55 Belgian Francs, 4.31 French francs, 1.8775 German marks, 2.0270 Dutch guilders, 846.50 Italian lire, 201.50 Japanese yen and 1.7050 Swiss francs. The pound edged up to 1.9843.