The Group's aim is to identify, survey, protect and promote geological and geomorphological sites in the former County of Avon - the modern unitary authorities of Bath and North East Somerset, Bristol, North Somerset and South Gloucestershire. RIGS are selected for their educational, research, historical and aesthetic value.

Friday, 19 February 2016

Aust Pylon and Talus Works

With the pylon at Aust coming up close to its 50th anniversary it is time that National Grid and Trant Engineering Limited give the concrete pillars it is stood upon some major renovation. As part of these works, that will continue throughout 2016, the concrete causeway that leads from the old ferry crossing down to the pylon will be in constant use. 

Over many years soil and clay have accumulated at the base of the adjacent cliffs forming a huge bank pushing against the causeway. It was time for the bank to be removed. 

During the first two weeks of February I was on site with a watching brief both for water birds using the foreshore and for fossils as the bank (talus) was removed and laid out across the beach. Two dumper trucks and two diggers were involved in transporting the soil and clay down to the beach. It was laid in two long rows along the beach enabling me to look through it. 

Although there was some rock amongst the talus it was mainly slabs of shelly limestone rock that revealed some lovely bivalve fossils but nothing more. However, time on the beach did give me the chance to find plenty of Rhaetic bonerock – mostly containing the usual mix of tiny teeth, coprolites and fish scales. A few boulders revealed larger bone and shark spines. 

I will be transferring the finds to Bristol Museum & Art Gallery – hand size pieces will be used as handling objects for learning activities. The bank itself has been cut back three metres and to a 45 degree angle. This will help reduce the pressure of future soil and clay building up against the road.  The recent high tides have been washing through the talus and cleaning up any remaining slabs of limestone. 

Ed Drewitt. Thanks also to Joe Keating and Dave Marshall from the School of Earth Sciences, University of Bristol, who covered a day each.

                                                    Talus being cleared at Aust

                                                       Fossil shells at Aust

                                                          Bonerock at Aust

                                                       Shark spine at Aust

                                                Fossilised bone at Aust

Wednesday, 3 February 2016

Student reports new finds of a living fossil

The coelacanth fish, found today in the Indian Ocean, is often called a ‘living fossil’ because its last ancestors existed about 70 million years ago and it has survived into the present – but without leaving any fossil remains younger than that time. Now, some much older coelacanth remains have been uncovered in a fossil deposit near Bristol by a student at the University of Bristol. 

The Jurassic coelacanth Undina, similar to the new finds from near Bristol. Image credit Harry Allard

While working last summer in Bristol’s School of Earth Sciences, Harry Allard, a recent graduate from the University of Exeter, found remains of coelacanth fishes, ranging in size from juveniles to adults, in a section of Late Triassic rocks, dated at about 210 million years old, at Manor Farm, Aust, close to the first Severn crossing.

He discovered the new fossils in a large collection of fish and reptile teeth and bones, representing animals that lived in the shallow seas, and on the neighbouring landmass at that time when Bristol teemed with dinosaurs, and the landscape consisted of numerous tropical islands.
Harry said: “These fossils provide an amazing glimpse of an ecosystem which is so different from the contemporary landscape of south west England. It has been fascinating to look at the changing composition of that long-lost ecosystem.”

The Manor Farm site was created 15 years ago when the second Severn crossing was under construction and contractors excavated there to obtain road-building materials.  After the site was made safe, a section was dug out so geologists, and the public, could visit and learn about the local geology. One of the fossil collectors at the time, the late Mike Curtis of Gloucester, collected batches of sediment, and worked through the material to extract nearly 20,000 teeth and bones.

“Mike Curtis kept such excellent records that Harry was able to separate the collections into findings from five separate bone beds, each perhaps separated by a few hundred thousand years,” said Professor Michael Benton, supervisor of the project.  “This provides unique insight into a turbulent time, when seas flooded across the landscape, submerging much of Europe.  Dry land became shallow seas almost overnight, and the energy of the floods churned up the soil and rock below and deposited bone beds in some places.”

Tracking upwards through the five bone beds, Harry was able to show how the fish faunas changed through time, from being dominated by small sharks at first, and then switching to more thick-scaled bony fishes higher up.

“The coelacanths were smaller than the living coelacanth Latimeria,” said Chris Duffin, a fossil fish expert who was involved in the work, “but these fishes were quite diverse in the Triassic, and only dwindled in importance later.  They are most unusual, having gills and lungs, and moving both by paddling with their gills, and stilt-walking along the seabed as well.


‘Microvertebrates from the classic Rhaetian bone beds of Manor Farm Quarry, near Aust (Bristol, UK)’ by Harry Allard, Simon Carpenter, Chris Duffin, and Michael Benton in Proceedings of the Geologists’ Association(doi: 10.1016/j.pgeola.2015.09.002)