The Whiteadder Water around Preston Bridge traverses the junction between the largely fluviatile Upper Old Red Sandstone and the lagoonal Ballagan Formation. New spore evidence from the TWEED project suggests that the junction in this area is very close to the Devonian – Carboniferous boundary. Basaltic pyroclastic rocks and a lava, which occur at the stratigraphical junction, constitute the most northerly outcrop of the Kelso Lavas. A large sill-like intrusion of very fresh basalt, probably associated with the Kelso Lavas, is exposed 3 km to the SW in Borthwick Quarry, where spectacular columnar jointing, zones of fracturing and mineralization provide clues to the sill geometry, mode of intrusion and age relationships of potential international significance.

Read the Code of Conduct and Safety Guidelines and book your place …

Excursion title:

Duns

Date & time:

Saturday 14 July, 9am

Finish time:

5 pm Duns
6.15pm Edinburgh

Leader:

David Stephenson, Alison Tymon

Excursion aims and description:

The Whiteadder Water around Preston Bridge traverses the junction between the largely fluviatile Upper Old Red Sandstone and the lagoonal Ballagan Formation. New spore evidence from the TWEED project suggests that the junction in this area is very close to the Devonian – Carboniferous boundary. Basaltic pyroclastic rocks and a lava, which occur at the stratigraphical junction, constitute the most northerly outcrop of the Kelso Lavas. A large sill-like intrusion of very fresh basalt, probably associated with the Kelso Lavas, is exposed 3 km to the SW in Borthwick Quarry, where spectacular columnar jointing, zones of fracturing and mineralization provide clues to the sill geometry, mode of intrusion and age relationships of potential international significance.

Transport:

Coach

Meeting point:

Waterloo Place

Extra pick-up points:

Milton Road

First locality:

Car park on north side of Preston Bridge NT 786 568

Excursion route:

Whiteadder Water, downstream and upstream from Preston Bridge

Borthwick Quarry

Terrain, walking distance, height gain:

River-bank paths, flat quarry floor. Total walking 4 km, no height gain. Walking boots, or wellies if preferred

Specific or Medium- / High-Risk Hazards:

Fast-flowing river. Unstable quarry faces.

Control measures required to mitigate against any Hazards referred to above:

Do not fall into river. Keep away from quarry faces.

Hard hats or Hi-viz clothing needed?

Yes, both – for the quarry

May dogs be brought on the excursion?

Yes

Toilet information:

Grantshouse and Duns

Geological map sheet:

33E & 34

OS map sheet:

67

References:

BGS memoirs 33E and 34 – free downloads from BGS web site

View route map for EGS Excursion on plotaroute.com