Jan 112012
 
Malvern 2

I have been out the last couple of days undertaking fieldwork for a building stones project, but today I was treated to a glimpse of a gem of a little geological section being prepared. Those of us who work in geoconservation talk a lot about geodiversity but this must be the most geodiverse section I have come across. It is a trench, only about 100m long but displays rocks from the Precambrian, Cambrian, Silurian, Carboniferous and Triassic.

The trench runs across the crest of the ‘Malvern Axis’, a major monoclinal fold trending north-south through central England that brings up Precambrian (~677 Ma; Cryogenian) to the surface. The Malvern line separates the two Precambrian terranes of the Midlands Microcraton, Wrekin Terrane to the west and Charnian Terrane to the east, that forms the solid basement of England. These Precambrian igneous rocks are unconformably overlain by Middle Cambrian Malvern Quartzite, and then Upper Silurian (Pridoli) Raglan Mudstone, and Upper Carboniferous (Moscovian) Halesowen Fm. This sequence was folded and thrust during the Variscan Orogeny at the end of the Carboniferous into the north-south Malvern Axis. Extension during the Triassic produced normal faulting along the Malvern Line and deposition of Middle Triassic (Anisian) Bromsgrove Sandstone to the east in the Worcester Graben. All this is being exposed in just one 100m trench, albeit somewhat tectonically shortened.

Standing on the axis, this is the view to the east. In the trench, the light coloured material in the foreground is Precambrian Malvern Complex, succeeded by grey/green and grey Carboniferous, red Silurian muds and Triassic sands towards the car.

To the west, the white is Cambrian followed by Carboniferous and Silurian on the other side of the axis. Note that many of the lithological identifications are still tentative.

The section is still in the process of being created and is on private land, but should be stunning when finished.

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