A major collection of modern and contemporary art assembled by two of the 20th century's most prominent collectors is expected to fetch more than $85 million when it hits the auction block next month, Sotheby's said.

The sale will be led by Mark Rothko's 1951 canvas "No. 21 (Red, Brown, Black and Orange)," which Sotheby's expects could sell for more than $50 million.

Works by Andy Warhol, Pablo Picasso, Salvador Dali and other top artists from the collection of Pierre and Sao Schlumberger will also be offered at a series of modern and contemporary art sales in November.

"Their vision was entirely their own," said Oliver Barker, deputy chairman of Sotheby's Europe of the Schlumbergers, "a unique aesthetic that blended their European roots with their American experience."

Barker said the couple produced "one of the most important private collections of our time."

Pierre Schlumberger was a French oil industry tycoon whose father and uncle founded Schlumberger Limited, the world's largest oil field services company in 1926.

The couple married 1961 and Sao Schlumberger forged close relationships with artists, acquiring works by masters such as Warhol and Rothko.

Together they became patrons of the Pompidou Center in Paris, the Museum of Modern Art in New York and the Museum of Fine Arts, Houston, and helped fund the restoration of the Palace of Versailles in France.

They were the first patrons to commission Warhol for a silkscreen portrait, which became one of the pop artist's stock in trade, according to Sotheby's.

"Portrait Sao Schlumberger," rendered in Warhol's trademark quadruple style and for which the artist personally sought out Sao as his subject, who died in 2007, is estimated to sell for as much as $3 million. Pierre Schlumberger died in 1986.

Other highlights beyond the Rothko, which the couple purchased from the artist's estate and has not been seen in public for more than 40 years, include Jean Dubuffet's "Cite Fantoche," estimated at up to $6 million.

Picasso's 1956 painting of his children Claude and Paloma, which could sell for as much as $7 million, is expected to be another top lot.

The Schlumberger collection of some 90 works is among many highly anticipated offerings of the upcoming fall auctions.

Sotheby's announced last week it was selling Alberto Giacometti's iconic sculpture "Chariot," which could sell for in excess of $100 million.

Christie's has already announced two major Warhol works depicting Elvis Presley and Marlon Brando, which together it expects will take in $130million. Last week it trumpeted another contemporary offering, Jeff Koons' "Balloon Monkey," which is expected to sell for $20 million to $30million.

Highlights of the Schlumberger collection will go on view in Hong Kong and London ahead of an Oct. 22-24 special exhibition in its entirety in New York. Its first offerings will hit the block at Sotheby's Impressionist and modern art auction on Nov. 4, with other works sold at contemporaryart auctions through November 12. - Reuters