Marriott Corp. has dropped plans to build a major amusement park in Northern Virginia and may abandon the Washington area altogether as the site for a proposed $90 million "Great America" complex.

A hint of these developments was included in an earnings statement released by the Bethesda lodging and restaurant company yesterday, which showed a sharp 27 percent jump in profits for the quarter and six months ended Feb. 10.

In the formal announcement, company President J. W. Marriott Jr. revealed a decision to "write off" all development costs to date associated with a planned theme park in the Washington region, first announced six years ago.

When a company writes off an investment, it normally is a sign that management and auditors have doubts that such funds ever will be recovered from aviable business operation.

But Marriott left open the possibility that his company still might move forward with a regional park. "A final decision on a Washington area park will be made after the 1978 operating at our two existing parks" in Santa Clara, Calif., and Gurnee, Ill., Marriott said.

Vice President for Corporate Affairs Thomas E. Burke later elaborated on the prepared statement, revealing that the firm notified officials in Prince William County a month ago that Marriott had decided to abandon plans for a theme park on 515 acres near Manassas.

Marriott initially had picked a Howard County located in 1972, but that was rejected by local officials after some citizens protested about potential traffic congestion and crowding. the company subsequently purchased the Manassas site and reached tentative agreements on plans for a park with Prince William officials.

But Burke emphasized yesterday that Marriott "always" had preferred a site between the two cities of Baltimore and Washington, to tap a potentially larger market. In addition to zoning fights and disputes over highway access in Prince william County, Marriott's interest in Northern Virginia waned with the opening of two amusement parks near Richmond --presenting a competitive situation that could reduce visitors to Manassas.

A second attempt to build Howard County was rejected last year after another round of hearings and protests by some citizens. Since that time the company has been talking with officials and property owners in Montgomery, Prince Georges, Anne Arundel and even Howard counties about potential new sites.

Alice Humphries, a member of the Prince William County Board of Supervisors from Woodbridge and chairman of the board last year, said yesterday the Marriott decision was not a surprise but will be a loss to the county.

"We very much wanted Marriott here, because of the positive effect on the tax base. . . but the park should have been operational years ago and was stopped by a lawsuit over zoning," she said.

Members of the board met with state officials in December in a final attempt to seek ways of encouraging Marriott to keep the Manassas site.

"Prince William County has done all it can do," Humphries said. Zoning for the land involved now has reverted to agricultural use, she confirmed.

Burke said no decision has been made on disposition of the land owned by Marriott near Manassas, the cost of which was not revealed.

All other costs associated with the proposed area park -- $2 million-- were written off as a loss in the recent quarter, but were virtually offset, after taxes, by a gain on the sale of excess land adjacent to the California park.

"We're still talking to people . . we've just started at zero again in accumulating future costs associated with a possible park here . . . we're keeping our options open," Burke asserted.

He said the Washington area "is a great market, a vibrant community," but he also revealed that Marriott is considering at least one other East Coast market as a potential third theme park site.

The return on investment from the first two parks has not been up to company goals but should improve in 1978, Burke forecast.

Marriott's park write off had little impact on overall profits for the second quarter, which rose to $6.8 million (19 cents a share) compared with $5.3 million (15 cents) in the same period a year ago. Sales were up 14 percent to $313 million.

For the first half of the new fiscal year, profits rose to $19.7 million (54 cents a share) compared with $15.5 million (42 cents), and sales were up 15 percent to $589 million.

Marriott said pre-tax earnings in the recent quarter almost doubled despite a second consecutive year of bad winter weather. Most of the gains were attributed to "very strong" hotel business in a traditionally slow season and a strong rebound in restaurant profits.

Sun Line Cruises recorded a "good" gain in the quarter and a continued recovery for the Farrell's ice cream parlor-specialty restaurant chain "had a major effect" on a doubling of restaurant profits.

Airline catering sales suffered during recent snow storms, when many flights were canceled. The firm also said new "no-frills" service by there airlines between the Northeast and Florida "panalized profits," presumably through elimination of most food services.