In any delta, changes in the depth of water, variations in the rate or nature of sediment supply and alterations in the strength and direction of water currents are reflected in the character of the sediment laid down. If these factors change gradually, there should be a vertical transition from one rock type to another (ie relationship with depth mainly). The further out to sea, lighter (finer grained) sediment will be deposited due to the lower energy away from the dynamic river. Similarly, coarse grained sands are closer to the land as they are heavier and sink in higher energy environments. As this process continues and the delta front grows, it is logical to see that fine sediment deposited further out to sea will gradually be covered by coarser material. Generally, then, we have a cycle which coarsens as we travel up the sequence. This assumes no tectonic or sea level change factors which would influence the deposition style. The cycle model can be seen in Fig 8 and is recorded in the Saddleworth surrounding region (Oldham and Ashton areas) as shown in figure 9

Fig 8

Fig 9

After all these sediments were laid down in the upper Carboniferous, the formation of the supercontinent known as ‘Pangea’ caused the formation of mountainous in a process known as orogeny. This was caused by plate collision and compression which results in the uplift of land. This caused the rocks in Saddleworth to be folded and faulted which can be seen in the dipping beds in the Diggle exposures (next page). As a result, the Pennines were formed, a volcano was thought to exist over Dartmoor (leaving the remnant granite - radiometrically dated at 300-280 Ma yrs BP) and rocks all over the British Isles were folded and altered by extreme pressures and temperatures.

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