Abstract

Rock types and sedimentary structures in the New York Devonian nearshore marine Catskill Delta provide inter-relationships that can be used to identify other deltaic paleoenvironments. Triangular prisms with four rock types as end members were constructed in order to display the range in lithology existing in outcrops where a given sedimentary structure was identified. The structural prisms were then arranged according to the similarities and differences of their patterns. This arrangement resulted in a structural ranking: low rank-flute casts to high rank-oscillation ripples. A low rank signifies an environment of low energy and hydrodynamic unsteadiness (variability) whereas high rank indicates higher energy and a more hydrodynamically steady state. Siltstones, shales and mudstones tend to be associated with the former, sandstones and rudites with the latter. Lithologic and structural data have been reorganized according to an earlier field-based paleoenvironmental classification. Higher ranked structures and coarser sediments were significantly abundant in the delta front and distributary bar environments but significantly rare in the open shelf and prodelta environments. Just the opposite is true for the finer-grained sediments and low-ranked structures. The platform, estuarine and lagoonal paleoenvironments provide less well-defined patterns attributable to the greater range of energy levels operating there. These associations provide criteria that can help to distinguish the paleoenvironments in other marine deltaic settings.

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