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The East-Central Province is composed chiefly of the Black and Grand prairie belts of Texas and southern Indian Territory, each bordered on the west by a belt of upland timber known as "cross timbers." These are parallel north-south belts of dip plains developed upon the outcrops of the various Cretaceous formations. The latter are a series of marls, sands, and limestones, inclining to the east so gently that their dip is only slightly greater than the inclination of the Regional Coastward Slope. Such an arrangement produces broad areas of outcrop. The topography of the Black Prairie, established principally on the marls, is undulating. The topography of the Grand Prairie is established upon beds of firm subhorizontal limestone of vast areal extent. These limestone surfaces are mostly flat dip plains, passing into cut plains along their interior margins. They slope gently eastward, and are terminated coastward by low inward-facing escarpments composed of the strata of the next plain. The plains are faintly indented by drainways that are fed by longitudinal branches whose ultimate and active caletas rise along the inland-facing escarpments.

The interior of the Black Prairie is marked by a low inward-facing stratified escarpment which extends south from Sherman toward Austin. Although this does not exceed 200 feet in altitude, it is a marked break in the otherwise uniform surface of the adjacent areas. It is an outcrop of the Austin chalk, the only conspicuous semi-indurated bed between the interior margin of the Black Prairie and the sea. Its margin overlooks the narrow belt of the Eastern Cross Timbers.

The western or inland-facing escarpment of the Grand Prairie is a still more conspicuous feature in the Texas region, extending, as it does, from the boundary of Arkansas due west through Indian Territory to the ninety-eighth meridian, and thence south through Texas to the Colorado, in a much-lobed and crenelated line. From the Colorado it curves west around the southern edge of the Central Province, where it becomes the eastern escarpment of the Plateau of the Plains.

North of the Brazos the slopes of this escarpment, marked by many low stratified terraces, descend to the west at a low gradient and include the Glen Rose type of prairie, consisting of open stretches of country and the various upland belts of the Western Cross Timbers, which follow certain outcrops of sandy strata. The crests of this escarpment are produced by an outcrop of the Edwards limestone; its hardness relative to that of the underlying formations results in its preservation as the summit of the escarpments and as many circular outlying remnantal buttes, usually known as round mountains, along