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Carlson, R.C., 1995

Diagenesis of the Lisburne Group, northeastern Brooks Range, Alaska

Bibliographic Reference

Carlson, R.C., 1995, Diagenesis of the Lisburne Group, northeastern Brooks Range, Alaska: Lawrence, Kansas, University of Kansas, Ph.D. dissertation, 285 p., illust., maps.


Correlations of 18 surfaces of subaerial exposure of the Carboniferous Lisburne Group (Alapah and Wahoo Limestones) in northeastern Alaska were used to reconstruct platform paleotopography. Southward increase in thickness of the Alapah Limestone shows minimum relief of 150 m on the sub-Mississippian unconformity beneath the Lisburne. In the lower part of the Lisburne a 100 m relative rise in sea level was followed by a 100 m relative fall. This was followed by overall relative rise of sea level and northward onlap. Later, southward progradation of the shelf is recorded by progressively more laterally extensive subaerial surfaces. Minor southward-sloping relief existed during later deposition (Wahoo Limestone). One subaerial surface is coincident with the Mississippian-Pennsylvanian boundary. The end of Lisburne deposition is marked by the sub-Permian unconformity on which 60 m of erosional relief occurs toward the south. The relative sea-level history of the Lisburne shows limited correspondence to a proposed global sea-level chart suggesting absence of global synchroneity. Crosscutting relationships, stratigraphic distribution, low concentrations of Mg and Sr, and depleted [delta]18O compositions (mean of 6‰) of early calcite cements show that most cementation in the Lisburne occurred during the Carboniferous and sub-Permian subaerial events. Quartz and later calcite cements postdate the sub-Permian unconformity and fill the remainder of porosity. The cements postdate compaction features, postdate some shear fractures, and the calcites have depleted [delta]18O compositions, some of which are similar to Lisburne marble. These features indicate precipitation during deep-burial to tectonic conditions. Formation of cavernous porosity at the Alapah-Wahoo boundary occurred during or after tectonism in the northeast Brooks Range. Lateral variability of meteoric calcite cathodoluminescence zones suggests correlations are diachronous and record variation in aquifer redox conditions. Variations in climate and amount of relative fall in sea level do not appear to have greatly affected meteoric calcite cementation and porosity occlusion. Grain type and perhaps lithology had some control, however; most meteoric calcite cementation occurred where subaerial exposure was most common and prolonged. This indicates that high porosity may be preserved in downslope carbonate reservoirs.

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