Forest physiography; physiography of the United States and principles of soils in relation to forestry . inctly lower than that ofthe old peneplain and resulted ultimately in the formation (late Tertiary) of local base-leveledsurfaces, essentially coincident with the Coastal Plain and continuous with an uneroded outerarea lifted so slightly above sea level as to suffer no important modification during this ero-sion period. This Tertiary base-leveling while extensive was not complete, and many rem-nants of the older and higher surface still project above the common level. After the partial deve
Forest physiography; physiography of the United States and principles of soils in relation to forestry . inctly lower than that ofthe old peneplain and resulted ultimately in the formation (late Tertiary) of local base-leveledsurfaces, essentially coincident with the Coastal Plain and continuous with an uneroded outerarea lifted so slightly above sea level as to suffer no important modification during this ero-sion period. This Tertiary base-leveling while extensive was not complete, and many rem-nants of the older and higher surface still project above the common level. After the partial development of a Tertiary peneplain there came adepression of the entire region of sufficient amount to allow the forma-tion partly by river aggradation, partly by marine deposition, of a greatblanket of silts, sands, and gravels (the Lafayette formation), which stilloccurs widely distributed throughout the region, its materials forming thesurface soil to a large extent.^ The process of excavation of the material constituting the CoastalPlain has gone on with but one interruption since the deposition of. The Lockesbure. Saratoga, Sulphuand Kisatchie wold:. Plood-Dlain andterrace area*. Fig. 212. — Prominent topographic features of the Gulf Coastal Plain in northern Louisiana and southernArkansas. (Veatch, U. S. Gaol. Surv.) the Lafayette formation. Through either climatic change or crustaldeformation or both the streams of the region after cutting out valleysbegan to aggrade their valley floors, but after the partial filling of thevalleys reexcavation was begun. The result is that the streams are 1 A. C. Veatch, Geology and Underground Water Resources of Northern Louisiana andSouthern Arkansas, Prof. Paper U. S. Geol. Surv. No. 46, 1906, p. 46. ATLANTIC AND GULF COASTAL PLAIN 533 generally intrenched below the level of the uppersurface of the alluvium which now occurs interrace form fringing the borders of the valleysand constituting an intermediate level of benchland of consider
Size: 2248px × 1112px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
