A sedimentary rock is a product of its provenance and transportational mechanisms as well as of its environment of deposition. As such, a sedimentary rock reflects the physical and chemical conditions under which the sediment was transported, deposited, and buried. The combined factors of size, energy, and water depth give an indication of the environments of deposition and these factors are represented directly or indirectly on the IES log (in the Gulf Coast, the "base line" corresponding to impervious beds is commonly shale, and peaks on the left correspond to pervious beds, commonly sandstone). Therefore, it is necessary to know graphically the environmental transitions and configurations as shown on the log. These transitions are of three general types. Type a appears to be the most common transition in Gulf Coast stratigraphy and exemplifies an abrupt change from one size fraction to another; therefore this transition indicates an abrupt environmental change or a local unconformable surface. Type b is a gradual transition from sandstone to shale or vice versa through an interbedded sequence of sandstone and shale. On a local scale this transition could be attributed to a gradual regressive or transgressive oscillation. Type c is the least common and most difficult to recognize. This transition suggests a gradual size change (i.e., graded bedding) and could appear at the top of a transgressive phase or the base of a regressive phase. Hence nine different combinations, with minor modifications, are possible in a sandstone-shale sequence and these are u ed to interpret the possible environments of deposition of the beds.

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