--> ABSTRACT: The Effects of Accommodation, Base Level and Rates of Peat Accumulation on Coal Measure Architecture and Composition, by Ron Boyd, Claus Diessel; #91020 (1995).

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The Effects of Accommodation, Base Level and Rates of Peat Accumulation on Coal Measure Architecture and Composition

Ron Boyd, Claus Diessel

The key to interpreting non-marine stratigraphy is the recognition that accommodation varies here much as it does in the marine realm, and that the sediments deposited reflect that variation by responses in facies organisation. The majority of sedimentary responses reflect movements in base level and resulting graded stream profile adjustments. Base level falls lead to a loss of accommodation resulting in incision and valley formation, while subsequent rises in base level generate increasing accommodation. The incised valley is flooded and successively finer-grained sediments are formed in a set of parasequences whose stacking pattern reflects the initially accelerating, then decelerating relative rise in sea level until highstand is reached.

Peat may form at any stage during the eustatic/depositional cycle but, if accommodation is sufficiently high, it may exceed the ability of the peat to fill the available space, and the mires and adjacent flood plains may be replaced by lakes. The ability of peat to take up the available accommodation is dependent on peat accumulation rates. A systematic correlation exists between peat accumulation rate and climate with a general increase from very low rates in subarctic regions to higher values in the tropics. Optimum development of peat deposits is thus dependent on the matching of the local peat accumulation rate with the local accommodation rate generated by eustasy and subsidence.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995