CSX Corp. yesterday reported net earnings of $101 million ($1.01 per share) for the third quarter, up from $94 million (91 cents) for the same period a year before.

Last year's third-quarter earnings included a one-time, after-tax gain of $34 million (33 cents) from the sale of Rockresorts Inc. Without that sale, CSX would have earned $60 million in the third quarter of 1989, making the year-over-year gain 68 percent, the transportation company said.

The company reported revenue of $2 billion for the third quarter, up from $1.89 billion in the same period a year ago. CSX noted that the company's rail, barge and container-shipping units all posted higher earnings despite the weak overall economy.

Rail operating income increased by 20 percent to $132 million, compared with $110 million a year ago, when third-quarter earnings were hurt by a strike against the Pittston Coal Group Inc. and damage caused by Hurricane Hugo. Traffic fell slightly, but some shippings, including autos and chemicals, were up.

CSX reported net earnings of $287 million for the nine months ended Sept. 30, down from $327 million for the first nine months of 1989.