Investigation of the physical stratigraphy of the Middle and Upper Devonian of southeastern New York has shown that this sequence of the "Catskill Deltaic Complex" might be separated naturally into a set of sedimentary domains. The North Point (lowermost Upper Devonian), one of these domains, is characterized by rhythmic patterns in sediment color, texture, and petrology; sedimentary structures; sediment transport directions; lithologic sequences; and lithosome geometries. The rhythmically recursive sequence of the North Point consists of (in ascending order): (A) polymictic conglomerate, (B) gray conglomeratic subgraywacke, (C) gray subgraywacke, (D) red subgraywacke, (E) red siltstone, (F) red mudrocks, (G) olive mudrocks, (H) gray mudrocks, and (I) sub-protoquartzite.

Various physical and statistical models of source, distribution, accumulation, and modification realms of the process-response system of the North Point were simulated on an electronic computer. The algorithm for a model of the process-response system of a rhythmic sequence, obtained by integration of relative aspects of these models, may be approximated by six sub-sets of equations; each sub-set is an attempt to characterize the status of process elements in the development of a response phase.

Translated into operational format these phases are: (1) early regressive phase (units A, B,); (2) middle regressive phase (B, C); (3) late regressive phase (D, E); (4) paralic stability phase (E, F); (5) early transgressive phase (G, H); and (6) late transgressive phase (H, I). The general aspect of this model is coarse-grained sediments (A, B, C) passing upward into finer sediments (E, F, G, H), forming a platform sequence which is rhythmically recursive. Homogenization at the strand zone and re-organization on the distal portion of the platform produces an inverted sequence (fines grading upward to coarser units). This model recognizes two components of subsidence, local and regional, as dominant process elements of the accumulation realm. The regional component is decomposed into he effects produced by compaction of the underlying sediment pile and those produced by subsidence of the Devonian sub-basin. The local component results from surface and near-surface compaction of sediment deposited during phases 3, 4, and 5 (units E, F, G, H) of a rhythmic sequence. The algebraic sum of the interaction of these two process elements may have profound effects on the character and mode of the response, producing transgression in one part of the domain, while regression or stability characterizes another part.

Within the framework of this model the rhythmic character of the North Point is thought to be the response to the interaction of: (1) source contribution activity; (2) design of transport and dispersal systems; (3) influence of sub-basin and platform dynamics on the character and mode of the accumulation; (4) modification of the accumulation by processes such as compaction, erosion, diagenesis, and structural adjustments.

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