Geology of Pembrokeshire

Pembrokeshire Geology Field Trip CAMBRIAN The Cambrian rocks in the genus Ara of Pembrokeshire can be divided into 3 stratigraphic ranges. These consist of Lower, put and Upper Cambrian. each(prenominal) originates from marine conditions, mainly of shallow marine sediments deposited on the grey shelf margin of the Welsh Basin. The Lingula Flags Formation, Menevian assemblage, Solva Group and Caerfai Group wreak the Cambrian ranges of Pembrokeshire (in the order of youngest first). Caerfai Group (Lower-Cambrian) This group consists of base Conglomerate, St Nons Sandstone, Caerfai Bay Shales and Caerbwdy Sandstone. The Basal Conglomerate is a ruddy saturnine aqueous rock that has clear joints and bedding planes. in that location argon large clasts that are enclose in the rock which are about 1 20cm in diameter. These are quartz, feldspar and rhyolite period of time bands. The rock is classed as a conglomerate as the clasts are held in a better matrix. Calcit e mineral veins were also gross on the rock face. bigger clasts were sit at the poll of the rock and smaller clasts at the bottom making it a transgressive sequence. The Caerfai shale has a red/garden pink colour due to the charge of oxidised iron. It is a powdery sedimentary rock with both(prenominal) mineral veins establish.

The mineral veins are approximately 3cm thick. Crystaline tuff is present through let on the rock, which is fused volcanic ash in which lechatelierites and crystal fragments predominate. The shale consists of 90 pct mud and 10 percent silt. Organisms strike removed sedimentary structures, as the rock is bioturbated. Laminations, flame structures, accuse st ructures and asymmetrical ripples were prese! nt throughout the shale. Finally, trace fossils in the unionise of vertical burrows were present running through the ash. The Caerbwdy Sandstone is present on a work shift surrounded by St Nons Sandstone and Caerfai Shale. There are threefold planes of faulting and it is quite difficult to make out the bedding. The massive...If you want to arse around a full essay, order it on our website: OrderEssay.net

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