stratigraphy and oil shale potential - Geology Ontario

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similar to the basal shales of the Marcellus. The interbeds
are l to 10 cm thick and usually occur 10 to 15 cm below the
base of the Marcellus. The organic shale interbed (in the
Dundee) encountered in drillhole OGS-82-3 had a TOG content of
3.8%. Immediately beneath the interbeds are 0.5 cm thick
horizons of concentrated bioclastic debris. These suggest
that a minor break occurred in deposition between each cycle
of carbonate and shale. The upper contacts of the organic
shale interbeds are sharp.
Unit E - Lower Organic Shale
This is the lowest Marcellus Formation unit present and
is a brownish-black fissile shale. "Although it appears to be
the darker coloured of the two organic shale units present (A,
E), it has the lower average TOC content (4.14% compared with
T.38%, see Table 5)". A brownish hue noted on some bedding
planes in unit E results from concentrations of flattened
amber coloured spore cases. Apart from this microfossil
material, the unit is poorly fossiliferous.
This interval has an average thickness of 0.45 m, varying
between 0.15 m in OGS-82-3 and 0.68 m in M-8 (see Table 6).
From the correlation of the OGS drillholes, (Fig. 12), this
unit appears to thicken in the central part of the subcrop
area underlying land. The upper contact of unit (E) is
gradational with the overlying Lower Shale (unit D).