The American painter Richard Diebenkorn, who died in 1993, is best known for his “Ocean Park” series, a group of 140 large-scale abstract geometric oil paintings of the California landscape made between 1967 and 1978, widely celebrated for their sun-drenched palette and architectural composition. Now a new small but exhilarating show at the Grey Art Gallery in New York (moving to the Phillips Collection in Washington this summer) brings to light an earlier turning point in the artist’s career, one that foreshadows the magnificence of his later achievements.

Diebenkorn in New Mexico: 1950-1952 brings together 19 paintings, 24 works on paper and one sculpture completed while the artist was at the University of New Mexico in Albuquerque. Although it documents only a fraction of the artist’s oeuvre it confirms a virtuosity that deserves to be better known, in America and beyond.

Diebenkorn began his studies at Stanford University in 1940, where he started working in a representational style close to Arthur Dove and Edward Hopper. In 1943 a Marine Corps officer training programme introduced him to mapmaking and cartography: from then, irrigation patterns, geological formations and aerial photography would all contribute to the development of the artist’s particular vision. After the second world war he joined the faculty at the California School of Fine Arts (now the San Francisco Art Institute), where Mark Rothko, Clyfford Still and Ad Reinhardt were also among the up-and-coming artists who had been hired. But in 1950, with hopes of painting full-time, Diebenkorn decided to leave San Francisco to pursue a master’s degree at the University of New Mexico: this self-imposed exile to the south-west was a deliberate move away from the dominant influences of the New York School and the burgeoning west coast art scene.

Diebenkorn’s New Mexico paintings and drawings have been compared by American critics to the work of Willem de Kooning (specifically his black and white series) and Arshile Gorky. But there is a buoyancy and levity in Diebenkorn’s technique that set him apart from the gravitas of his east coast colleagues. Diebenkorn experimented vigorously with the density and application of paint, producing beguiling atmospheric effects. Like Jackson Pollock, sometimes he splattered the paint directly on to the surface of the raw canvas; at other times he stained it, à la James Brooks, cutting the oil paint with turpentine to the point where it began to behave like gouache or watercolour.

In contrast to the opaque impasto that was Clyfford Still’s trademark, there was a translucent fluidity to Diebenkorn’s use of paint, and a considered and daring approach to colour. The artist himself may have described the Albuquerque paintings as subdued and austere but these dappled canvases meld their soft veils of colour with flashes of tangy pinks, emerald greens and every imaginable shade of yellow.

It is easy to forget that these paintings are first and foremost landscapes. Unlike many abstract expressionist paintings, the forms that articulate Diebenkorn’s compositions were derived not so much from surrealist automatism but, rather, from what he saw around him in New Mexico, the organic modernist structures of the local adobe architecture and the brilliant hues and dramatic forms of the Sandia Mountains.

It is old news by now that many artists associated with the famous New York School were not actually from New York, and exhibitions and books have deftly taken apart the myth that the abstract expressionist movement was solely associated with the east coast. This exhibition celebrates once again the multiplicity and variety of this movement, confirming again that the most interesting histories of abstract expressionism are those being told from the sidelines rather than any so-called centre.

‘Diebenkorn in New Mexico: 1950-1952’, Grey Art Gallery, New York University, until April 5 (tel: + 1 212-998- 6780). Phillips Collection, Washington DC, June 21-Sept 7 (tel: +1 202-387 2151)