Founded 1858 | Promoting public interest in geology and advancing geological knowledge
Founded 1858
The rocks exposed around Portencross are mainly sandstones (known across the UK as the ‘Old Red Sandstone’ (ORS) dating back to the Devonian Period (420 to 360 million years ago). The ‘Lower Old Red Sandstone’ was deposited in desert environments in the aftermath of the Caledonian Orogeny when Scotland (on part of the North American continent called Laurentia) collided with England and Wales (on part of the European continent called Avalonia), closing the intervening Iapetus Ocean. The collision was marked by major strike-slip faulting and considerable local volcanism. Later in the Devonian there was a further period of mountain building (the Acadian Orogeny) when Iberia collided into Avalonia further south. This resulted in more uplift and renewed sandstone deposition (the ‘Upper Old Red Sandstone’). On the walk we will examine, compare and contrast the Lower and Upper Old Red Sandstones and also look at some of the igneous rocks.
The trip will be in three sections: a walk from the meeting point at Yonderfield Farm to the east end of Ardneil Bay and back, move vehicles to Portencross, then out-and-back walks to the south and north of Portencross from the main car park at Portencross.
The Strathclyde Geoconservation Group (a Subcommittee of the Society) have produced a draft explanatory leaflet for the central part of the area around the castle and one of the objectives of the trip is to review this leaflet before it’s published. We will also discuss how the locality can be portrayed on the new ‘Geosites’ database being developed by the Scottish Geology Trust.
Own transport. Car sharing from Glasgow recommended where possible.
At Yonderfield Farm. https://maps.app.goo.gl/bSQ95kSv46fNdsKh6
Late arrivals should go to Portencross carpark and await arrival of the group. https://maps.app.goo.gl/Tf7cTnjtPQLrtUqeA
10:00am – 4pm
Walk down to east end of Ardneil Bay the to examine the Upper ORS, an igneous dyke, and other interesting features. Return to vehicles.
Move vehicles to Portencross carpark and walk out and back over Farland Point to the NW end of Ardneil Bay
Examine lowest Upper ORS, a large dyke and the ‘inlier’ at Sandy’s Creek. Discussion of the Largs – Portencross Fault.
Return to carpark and have lunch (bring packed lunch).
Walk along shoreline to Portencross Castle (possible visit inside). Various fault lines and the Lower ORS succession.
Follow coastal path to the pier. Various sandstone bodies and a dolerite dyke.
Continue to follow coastal path north as far as gates to Hunterston to examine faults, igneous intrusions and the Upper ORS conglomerates.
Optional walk up Goldenberry hill for spectacular views, Hunterston Power Station, Wirral subsea Interlink and some more local geology (reasonable fitness and agility required)
Level 1: Multiaccess – “All users including people with reduced mobility.”
Level 2: Easy – All levels of fitness and family groups including children and the elderly
Level 3: Moderate – “People with a moderate level of fitness.” An amount of walking over beach boulders etc
Level 4: Strenuous – “People accustomed to walking rough trails and with a high level of fitness.”
Mostly Level 2, but 3 if the optional hill walk is included. The section from Portencross carpark past the castle is Level 1. Generally the coastal walking here is straightforward and is suitable for those with limited mobility and a return to vehicles can be made at any point.
Section 1: Out and back to Ardneil bay from Yonderfield – 2 km
Section 2: Out and back to Farland Point from Portencross car park – 1 km
Section 3: out and back from Portencross car park to Hunterston gate – 3.5 km
Total Walk 6.5 km. (excluding optional hill walk)
While there are no toilets at the location, there are public toilets in West Kilbride (Glen Road), which is a 5-minute drive from Portencross. Suggest using them before arrival and there will be an opportunity at lunch time to drive to the toilets if required. https://maps.app.goo.gl/fjceYuPTQ6NNTRbE9
