New York's week of contemporary art auctions came to an upbeat close Friday, with collectors taking home more than $700 million of new art at Sotheby's, Christie's and Phillips de Pury & Co. The total trounced the previous week's $400 million series of Impressionist and modern sales and highlighted the leading role contemporary sales are playing in the overall recovery of the art market.

The field of contemporary art is perennially volatile, stocked with artists whose claims...