SH3862 : The rock 'melange' at Porth Twr Bach

taken 1 year ago, near to Llanddwyn Island/Ynys Llanddwyn [other Features], Isle of Anglesey, Great Britain

The rock 'melange' at Porth Twr Bach
The rock 'melange' at Porth Twr Bach
The amazing rocks on this small beach were first described as a 'melange' by the geologist Edward Greenly, who published a geological survey of Anglesey in 1919. The rich variety of rocks here include rose pink quartzites, greenish lavas, pale limestones, dark coloured intrusive dykes, and purple manganese rich shales, all in a colourful mix within a small area. It appears that these rocks were once on an ocean floor and were dragged deep into a trench [subduction zone] at the point where two plates collided. Subsequent earth movements have seen the rocks shifted further and have allowed the intrusion of dykes. This is a geological site of world importance.
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SH3862, 152 images   (more nearby )
Photographer
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Date Taken
Monday, 3 July, 2017   (more nearby)
Submitted
Thursday, 13 July, 2017
Geographical Context
Coastal  Geological interest  Islands  Estuary, Marine  Rocks, Scree, Cliffs 
Subject Location
OSGB36: geotagged! SH 3859 6241 [10m precision]
WGS84: 53:8.0602N 4:24.8532W
Camera Location
OSGB36: geotagged! SH 3857 6240
View Direction
East-northeast (about 67 degrees)
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Image Type (about): geograph 
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