Rocks on the west side of Broughton Bay – Part 3

Rock textures and fracture patterns in Gower Carboniferous Limestone

Some more images showing the mixed-up nature of the upper rocks in the exposure of Hunts Bay Oolite Subgroup of the Carboniferous Limestone in the cliffs at the west end of Broughton Bay on the Gower Peninsula – illustrating the irregular fracture patterns, rough textures and combinations of rock type within the formation. I am considering whether these messed up rocks represent a storm event way back at the time they were forming?

According to Willoughby, C (1996) Environments of Deposition in the Carboniferous Limestone of South  East Gower:

In the sequence of the Hunts Bay Oolite there is also further evidence of storm events with the appearance of bends and lenses of coarse laminated packstones*. These are associated with breccias* comprised of angular fragments of coarse oolites in the packstone matrix, indicating hardground formation before these have been ripped up in storm events and rapidly redeposited within reworked packstones. In places the junctions between these two lithologies are gradational, probably indicating that the sea floor at this time was uncemented and soft allowing mixing to occur.

I visualise that scenario as resulting in something that looks like pack ice,  where a solid sheet of ice has been broken up by some force of nature into many angular fragments that then refreeze into a solid form with the pieces ‘cemented’ together by newly formed sea ice.

Definitions

* Breccia is coarse, clastic, sedimentary rock, the constituent clasts* of which are angular. Breccia literally means ‘rubble’ and implies a rock deposited very close to the source area.

* Clasts are particles of broken-down rock. These fragments may vary in size from boulders to silt-sized grains, and are invariably the products of erosion followed by deposition in a new setting.

Packstone is defined by the Dunham Classification as a limestone characterised by a grain-supported texture, together with a lime-mud matrix.

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

Rock textures and fracture patterns in Gower Carboniferous Limestone

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4 thoughts on “Rocks on the west side of Broughton Bay – Part 3

  1. Pingback: Brachiopod Fossils in Hunts Bay Oolite at Broughton Bay | Jessica's Nature Blog

  2. Pingback: Rocks & Pebbles near Twlc Point | Jessica's Nature Blog

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