The East Texas area, which might be considered as the humid portion of the central dissected belt of the Coastal Plains of the United States, comprises the Sabine Uplift area, the East Texas basin, and the rolling plains southward as far as the coastal prairies. These areas may be separated from the rest of Texas roughly by a line extending from the Red River in north central Lamar County southwestward to east central Limestone County and then southeastward to Galveston Bay. Most of East Texas is forested, and except the post oak plains, the majority of the forests belong to the mixed type of shortleaf pine and hardwoods. Southward, however, along the southern margin of the dissected plains, a tongue of longleaf pines extends into Texas from Louisiana. The longleaf portion of East Texas is an area of deep sands underlain at a depth of several feet by well-drained sandy clays. Still farther south, extending into the edges of the flat coastal country east of Houston, is a forested area composed of an admixture of loblolly pines and water-tolerant oaks. The broad lowlands paralleling the larger streams that flow across East Texas are characterized by a heavy growth of hardwood forests (see LUMBER INDUSTRY). Most of the upland soils of the central dissected belt of East Texas are highly leached. The majority of the soils have yellow subsoils, the surface soils being grayish in aspect. Red soils occur in exceptional areas, such as on slopes underlain by calcareous materials; such soils may be red from the surface downward to the unoxidized parent materials. The Sabine Uplift district is a mixed forest area underlain by sandy clays. Geologically it is a domal area, and its structural relations are important to the accumulation of oil and gas. The large Panola gas field is situated in the Texas portion of the uplift. The East Texas basin overlies a syncline that is, in a structural sense, a complementary feature to the Sabine Uplift. This district comprises the redlands hilly country of East Texas lying west and north of the Sabine Uplift and the post oak plains district between the redlands hilly country and the black prairies. The post oak plains district is a dissected area underlain in part by glauconitic beds together with limy materials. The flat tops of the hills overlooking the wide intervening rolling lowlands apparently are remnants of a former plains surface, held up by a caprock of iron-ore beds that margin these hills, forming a layer resistant to erosion. The intervening lowlands are underlain by sandy clays. Where underlain by greensand marls, the soils are usually red in color, some of them being the deepest red of all soils found in the United States (see SOILS). One of the most important oil regions of the nation, the East Texas basin, includes the gigantic East Texas oilfield, the interior salt dome fields, of which the Van field is the largest, together with the fault line fields-the Mexia and Powell oilfields-on the western margin of the basin, as well as Talco and Sulphur Bluff along the northern margin of the basin. On the northern margin of the Sabine Uplift is the Rodessa oilfield that continues northeastward through the corner of northwest Louisiana into southwestern Arkansas. The Hawkins pool in Wood County is also in the East Texas basin. All of the production in the East Texas basin is from the Cretaceous except for a small amount from the Jurassic near the Louisiana line. The large production, including that from the East Texas field and most of that from Van, is from the Woodbine sand, the basal beds of the Upper Cretaceous, which outcrop to the westward in the Eastern (or Lower) Cross Timbers.