December 26, 1985

Archeologists working here have discovered an English-style Renaissance garden dating from 1680 with a central broad walk of sand, the earliest documented formal garden in America. Last June, in the excavation of what was assumed to be a 19th-century garden, test holes turned up a concentration of 17th-century pottery shards, wine-bottle fragments and seals. The distribution pattern of artifacts under the sand paths was uninterrupted, and the archeologists realized that the fragments could have been deposited only at the time of construction. They had found a second, older garden.

THE 29th Gold and Silver Ball was no stereotypical teen-age get-together. But the gathering of East Coast prep and public school students eager to rock into their Christmas vacations has become an annual opportunity to discover what fashions fit the mood of sophisticated youth. This year conformity was revealed as the rage, and cool was a matter of quiet sophistication. No one crashed. The only casualties in the infirmary were two broken bra straps. Though some smooched in dark corners, not a single jaded youth was seen sipping from a flask, despite the fact that only soft drinks were served. And when the rare political opinion was expressed, it was likely to reflect Reaganism. Yet for the thousand-plus 14- to 19-year-olds who attended this year's benefit for the Youth Counseling League at the Grand Hyatt Hotel Sunday night, the $125-a-ticket black-tie dance was still an occasion to let loose.

At least 53 people were reported today to have been killed when 2,000 Zulus clashed with 3,000 members of the Pondo tribe in what police officers called the worst factional fighting in years between tribes in South Africa. A police spokesman said the fighting, reportedly involving combatants armed with spears, knives and possibly firearms, erupted Tuesday night at Umbumbulu, 20 miles south of Durban on South Africa's Indian Ocean coast. The reasons for the fighting remained unclear tonight. Clashes have arisen in the past over such issues as water rights, but there was no indication tonight if that had set off the latest dispute.

Among the 150 worshipers at the 11 A.M. mass yesterday at St. Joseph's Roman Catholic Church on the Upper East Side were two women who were not scriptural readers or communion servers but were nonetheless important to the church this Christmas. One was Pam Shiells, a 38-year-old bank administrator in her ninth month of pregnancy. Mrs. Shiells had not been to church regularly for five years because, she explained, ''I think I just got lazy.'' But she returned, she said, partly because Christmas was a time she wanted to ''feel close to God'' and partly because ''I want to raise my child a Catholic.'' A Lawyer The other woman was a slender, well-dressed lawyer in a fur coat accompanied by her 7-year-old daughter. The woman, who did not want to give her name, described herself as a lapsed Catholic who grew angry with the church in her college days because she found its sermons outdated.

Companies The GAF Corporation raised its all-cash tender offer for the Union Carbide Corporation to $74 a share, from $68. Analysts say the new offer is roughly equal in value to a package of cash and securities that Carbide offered for 35 percent of its shares. [Page D1.]