Tectonic pulsing

Dolomite cement components were all sourced from outside the sand body, most probably from local or basinal mudrocks. Stable isotope data indicate a mixed organogenic-marine carbonate source, and precipitation at relatively low temperatures (s70°C, if pore fluids were sourced from clay mineral dehydration reactions during deep burial of Carboniferous mudrocks in the Rathlin basin 55°C if they were locally sourced). Thermobaric mass transfer was enhanced by tectonic pulsing and dolomite precipitation was driven by CO2 degassing. 

The Venezuela samples are higher in Sr/ Sr than present-day seawater probably reflecting tectonic pulses. Fig. 7 connecting the prograding Red Sea strontium isotope values and those of the Caribbean Plate (Los Roques Island, Venezuela) (note dashed line in Fig. 7) generates an approximate strontium isotope stratigraphy for much to most of the Holocene. 

The pulses of increased clastic influx reflect tectonic activity, as has been suggested by Ettensohn and Barron (30, 31), but with the addition of a northwestern landmass to provide material west of the general line of the Algonquin and Cincinnati Arches. These pulses are represented by the upper wedges (B/C). Between pulses, there was widespread deposition of the "lower black" (A) type of shales which, for the lower Antrim and lower Sunbury equivalents, were little influenced by arches. The southwestern source suggested by Ettensohn and Barron for the Appalachian Basin (30) seems very plausible for the "lower black" shales (A) of the Illinois and Michigan Basins as well. 

The 50 million years of the Devonian Period provided sufficient time for over 11,000 feet of sedimentary rocks to accumulate in the Appalachian Basin this accumulation was controlled by pulses of tectonic uplift to the east. A similar control of a northwestern source area by intermittent tectonic movement is suggested as a source for the upper wedges (B/C) in the Michigan and Illinois Basins. The lower black shales (A) of regional type represent quiescent periods of slow deposition followed by relatively more rapid sedimentation occurring in response to uplift and erosion of source areas and to depositional restrictions caused by rising arches. The total thickness of Devonian shales in either the Michigan or Illinois Basin is less than 1000 feet, so that the sediment volume involved in these two basins is far less than in the Appalachian Basin. Thus there was ample time for... 

The mass transfer problem may be resolved if eogenetic pore fluids were transmitted locally across the GGF in response to fault-related changes in pore pressure and near-surface hydrology (e.g. Knipe, 1993). The cemented fractures at Ballycastle show clear evidence for elevated pore fluid pressures and hydraulic fracturing, and the pulsed nature of dolomite cementation implies a tectonic drive. Kerr (1987) commented on the likelihood that the GGF was active in the Late Carboniferous/ Permian. Argillaceous coastal plain sediments asso-... 

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