Field trip – 2nd April 2022: Ballynaguilsha Quarry and The Geological Survey of Ireland Core Store, Birr with Markus Pracht (Geological Survey Ireland)

IGA EXCURSION: BIRR AREA, CO. OFFALY

Ballynaguilsha Quarry and The Geological Survey of Ireland Core Store, Birr

Image credit: John Kelly

Click here for field trip notes.

ABSTRACT:

What is “Waulsortian Limestone”? We will discuss the Waulsortian as a facies and in the context of stratigraphy. What are the building blocks comprising the “Waulsortian limestone” in Ireland? We will try to visualize the geometry of the “Waulsortian”. How useful is borehole data? What are its limitations? The WA limestone facies can often (but not always) be divided into several sub-facies, depending on their relative position within the “WA complex” as seen in core or outcrop today and a simple terminology will be benchmarked against the outcrop in the quarry and later to the borehole. In the afternoon we will visit the core store of the Geological Survey of Ireland in Birr (picture on the left), where we will study the Grangegorman borehole (GSI-21-004). This borehole was drilled as an exploratory borehole to assess the potential for deep geothermal energy in the Dublin area. The borehole collared and penetrated 665m of basinal lithologies of (probably) Lucan Formation (Dublin Formation: Chadian-Arundian: Nolan 1986) followed by >330m of (probably) Tober Colleen Formation and terminated at 998m. The borehole is situated <200 meters to the north of the axial trace of the NE-SW trending Kings Bridge Anticline (Nolan 1986). This borehole was drilled in argillaceous limestone and dk-gy mudstone/shale. The argillaceous limestone and shale sedimentation in the Lucan Formation exhibits cyclicity (picture above). Detrital siliciclastics occur in some limestone and shales (especially in the Lucan Formation) but due to their grain size their extend is difficult to estimate.

MEETING POINT

Ballynaguilsha Quarry , Birr, Co. Offaly, 10.30am

ITINERARY

In the morning we will visit Ballynaguilsha Quarry to look at an outcrop of Waulsortian limestone.  In the afternoon we will visit the core store of the Geological Survey of Ireland in Birr, where we will study the Grangegorman borehole (GSI-21-004).

Date: Saturday 2nd April, 2022, 10.30 to 4pm.

Leader: Dr Markus Pracht (GSI)

Registration on a first come, first served basis with current IGA members having priority.

Please register HERE by Friday 25th March.

N.B. All attendees will be expected to follow Covid-19 government guidelines and the IGA Covid-19 guidelines.