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within lIle main foreland basin, and closer to the eastern margin of the basin, However,
caution should be applied in making regional reconsU'uctions along the length ollhe basin
using sand/mud ratios alone. in the light or' structural complexities involving: the
parautochthon (Slockmal and Waldron, 1990: Waldron and Stockmal. 1991)
The 1JJwer Head Formation was deposited during the Arenig to early lIanvitn
in an oversupplied basin or basins in which facies assodations characteristic of middle
and inner submarine fans were deposited.
Deposition was accompanied by uplilt,
probably along faults on the eastern margin of the basin.
It was also accompanied by
probable subaerial erosion of stratigraphically older units and supply of lhe eroded
material to the basin in addition to sediment derived from the main source of sallti.
ConU'ary to the suggestion ofGonzalez-Bonorino (1990), the Lower Ilead Formation was
probably deposited in a slope basin or basins separate from the main foreland basin 110ur.
The lack of lateral continuity of the formalion within the allochthon may support the
hypothesis that it was de~sited in several ihon discontinuous basins, rather than in one
long basin.
Although field sedimentology suggests that the Lower Ilead Formation was
deposited in a slope basin, as opposed 10 the foreland basin proper, prOVenatll:e studies
may provide independent evidence for this. If, as Gonzalez·Banorino (\990) suggtStS,
small fans in the Lower Head Formation were fed directly by small rivers, this mode of
supply might have resulted in a significant varialion in grain population supplied 10 each
individual iystem, which would suggest Ihat lhe Lower Head Formation might be
predicted to be petrographically heterogeneous. Clast populalions in the conglomeratic