Blog & News

REVIEW: Crawton Field Trip

Mon 11 June 2018

Category: Field Trips, Reviews

By Matt Jacobs, Lloyd’s Register

It was a sunny, calm and warm(ish) start to the PESGB field trip as enthusiastic members of the Aberdeen subsurface community gathered at Stonehaven Harbour prior to the short trip down the coast to Crawton B

 

ay. The trip – excellently organised and executed by Simon Gould – was to inspect the early Devonian coastal exposures which show the interaction between basaltic-andesitic lava flows and fluvial conglomerates of the Dunottar-Crawton group. With mountain goat-like precision, the group descended to the first location. At beach level there is excellent exposures of the contact between the Crawton Group conglomerates and sandstones and the overlying lowest lava flow of the Crawton sequence. This was the first glimpse of the size of the materials within the conglomerates, indicating the size and energy of the fluvial system transporting and depositing them. Several faults and joints also provide a very clear view of the structural aspects affecting the sedimentary sequence.

Moving up the sequence, location 2 provided great panoramic views of the lava flows, up close views of columnar jointing and – to the back drop of the very vociferous local bird life – Simon provided some great analogue discussion to the present day volcanic activity in Hawaii. The third location provided a great example of graded bedding in the conglomerates, rapidly fining up over an approximately 1m scale from large cobbles into pebble grade material. With the trip drawing to its conclusion and soaring temperatures approaching a balmy 13ºC, the thirsty group made its way to the last locality at the main beach. The last remnants of the Crawton lavas are found at beach level, before giving way to the Arbuthnott-Garvock Group which are magnificently displayed in the cliff section. The cliff section highlights an array of sedimentary features, providing real insight into the scale of the fluvial features within these Devonian systems.

There was just enough time for people to stock up their private rock collections from the beach, and to award the trip organiser with the highly sought-after piece of core from the PESGB, before returning to sunny Stonehaven to enjoy lunch and refreshments. All in all, a great field trip to look at some of the fantastic geological exposures to be found along the North-East coast of Scotland.