Martin Marietta Corp., braced with a "strong momentum" in the fourth quarter that exceeded the Bethesda company's forecasts, yesterday reported record sales and profits for the full year and final three months of 1978.

Three of the region's largest banking firms -- Suburban Bancorporation, Union Trust Bancorp and First Virginia Banks Inc. -- also had sharply higher and record-level profits for 1978.

A diversified construction materials, aluminum and aerospace firm, Martin Marietta earned $136 million ($5.54 a share) in 1978 compared with $102.1 million ($4.29) the previous year, a gain of 33 percent. Sales rose to $1.76 billion from $1.44 billion.

Fourth-quarter profits soared about 70 percent to $86.6 million ($1.44) from $21.5 million (85 cents) as sales rose to $507 million from $391 million.

Chairman J. Donald Rauth said that based on the recent gains, "it is fair, even conservative in my view, to say that Martin Marietta's prospects for the future are impressive," with continued gains expected this year.

Martin's aluminum division provided the largest proportional increase in profits, and four of the firms's five major businesses had record years -- aluminum, cement, specialty chemicals and construction aggregates. Aerospace sales rose but earnings were down from 1977, which had included a one-time $14.8 million performance bonus.

Rauth said the company did not experience a normal fourth-quarter decline in southeastern and western construction markets.

Earnings at Suburban rose 20 percent to $13.5 million ($2.92 a share) compared with $11.3 million ($2.45) in 1977, the Hyattsville company said yesterday. Suburban owns Suburban Trust Co., the largest bank based in the Maryland suburbs of Washington.

In the fourth quarter alone, profits rose 13 percent to $3.6 million (77 cents a share) from $3.2 million (69 cents), not counting gains or losses from securities transactions.

Chairman Robert Tardio said consumer and real estate lending expanded by a substantial volume, bringing in additional interest income. Total loan volume on Dec. 31 was $827 million, up 3 percent for the year.

Suburban deposits totaled $1.12 billion at the end of 1978 compared with $1 billion a year earlier, including STC's 63 offices and two smaller subsidiaries, Thurmont Bank and Peoples Bank of Hancock.

Union Trust Bancorp., a Baltimorebased holding company for Union Trust Co. of Maryland, said earnings doubled in the fourth quarter and rose 33 percent for the year.

Not counting securities transactions, Union Trust profits for the year were $8.4 million ($3.43 a share) compared with $6.3 million ($2.57) in 1977. Fourth-quarter earnings were $2.2 million (90 cents) vs. $1.1 million (45 cents).

Chairman J. Stevenson Peck attributed the earnings growth to a 10 percent increase in average loan volume accompanied by a 22 percent jump in interest income. Peck also noted that Union Trust had benefitted from costcontrols, as non-interest income was up 12 percent but expenses rose only 8 percent.

Assets of the company rose from $1 billion to $1.2 billion while average deposits gained 10 percent to $844 million. The Baltimore firm also owns Landmark Financial Services of Silver Spring, a consumer finance firm. Statewide, Union Trust has 82 offices.

First Virginia Bank operating profits in 1978 were a record $11.6 million ($1.10 a share), up 21 percent from $9.6 million (91 cents) in 1977. Fourth-quarter earnings rose 24 percent to $3 million (29 cents) vs. $2.4 million (23 cents).

Deposits of the Falls Church holding company's 20 member banks throughout Virginia rose 8 percent last year to $1.2 billion on Dec. 13 as loan volume expanded by 10 percent to $820 million.

Farmers & Mechanics National Bank, of Frederick, reported a 17 percent increase in profits last year to a record $1.84 million ($3.08 a share) from $1.56 million ($2.63) in 1977. Total assets rose to $218 million form $200 million, deposits rose to $218 million from $183 million and loan valume rose to $136 million from $116 million. F&M is the largest independent bank in the Frederick area with 13 offices in Frederick, Montgomery and Carroll counties.

Bank of Maryland, based in Hillcrest Heights, reported record profits of $702,355 ($3.29 a share) in 1978, up 31 percent from the previous year. Assets rose 15 percent to $80 million while loan volume expanded by 22 percent to $47 million. The bank has 10 offices in Prince George's and Montgomery counties.

State National Bank, of Rockville, said earnings last year were up 36 percent to $791,283 from $580,281 in 1977. A dividend of 36 cents a share was declared payable Jan. 31 to owners of record Jan. 26.

Manor Care Inc., a Silver Spring nursing home and health care firm, reported a 73 percent increase in profits for the first six months of its fiscal year, ended Nov. 30. Earnings were $852,000 (49 cents a share) compared with $493,000 (29 cents) a year ago as sales increased 29 percents to $22.7 million.

American Realty Trust, an Arlington-based real estate investment trust, reported operating profits in the year ended Sept. 30 of $919,973 (41 cents a share) compared with $29,090 (1 cent) the previous year. For the recent year, ART had a one-time tax credit of $840,000 that made net income $1.76 million (79 cents). Earnings last year included $1.28 million from the sale of properties compared with a similar gain of $325,263 the previous year.

Computer Data Systems Inc., a Silver Spring consulting and data processing services firm, reported earnings of $179,000 (33 cents a share) from continuing business in the six months ended Dec. 31 compared with $107,600 (19 cents) a year earlier. Sales rose $473,500 to $3.5 million and CDS directors declared a dividend of 6 cents a share, payable March 1 to owners of record Jan. 29.