Previous SiteNext Site

Six Mile WaterTyrone
No picture
Summary Full report
Site Type: Inland exposure
Site Status:
District:
Grid Reference: J31763848, J32623896
Rocks
Rock Age: Quaternary
Rock Type: Gravel, Sand
Interest
Other interest: No data, Deglacial sediments, Glacio-fluvial sediment, esker

Summary of site:

The Midlandian was the last major Irish glaciation. It commenced around 75,000 years ago and, with a couple of brief warm intervals, lasted until around 10,000 years ago. In the second half of this period, the ice that dominated the eastern half of Northern Ireland was centred on the Lough Neagh Basin, confined to the east by Scottish ice occupying the North Channel and to the west by an ice mass centred somewhere near Omagh. This meant that the Lough Neagh ice could only escape to the north and south. The axis separating these flow directions crossed the basin roughly along a line east north east/west south west across what is now Lough Neagh. The Six Mile Water valley was to the north of this axis in the northerly flow.

The deposits in the valley reflect late events in the final stages of the melting and retreat of this ice mass. They occupy a discontinuous belt on the northern flank of the valley up to a kilometre wide and 18 km long extending from just south of Antrim to the area immediately west of Doagh. At the Old Mill just south of Antrim there is a group of low hummocks up to 2 m high, a shallow kettle hole and a remnant of a ridge, all within an area of about 1 sq km. 3 km to the north between Dunadry and Ballybentragh is an area of streamlined ridges and mounds up to 15 m high, eroded in places, associated with dissected fragments of north east/south west orientated ridges over half a kilometre long and 8 m high. A further 2 km to the north east at Parkgate there is an area of around a square kilometre of hummocks and linking ridges with south east/northwest orientation, up to 6 m high. An old sand pit exposing these deposits reveals boulders, many of the local vesicular basalt bedrock. A further 2 km to the north east immediately west of Doagh there is a 6 m high ridge extending across the valley for 200 m associated with four segments of ridges at lower levels aligned with the valley axis. The only outcrop is at Parkgate where the deposits appear to represent three different sets of conditions, all associated with the late stages of melting of the Lough Neagh ice. The deposits in the middle of the belt from Dunadry to Parkgate appear to be survivals of deposits formed within the ice while the cross valley ridge west of Doagh appears to have formed along the ice margin. The hummocks and kettle hole south of Antrim town formed in the open. Towards the end of the Midlandian, fast flowing ice occupied the valley of the Six Mile Water and smoothed the valley bottom, walls and the debris accumulated between the glacierís base and bedrock. Following this episode, a tongue of largely static ice occupied the valley and all the features described are a consequence of this final phase of melting probably associated with a high water table (piezometric surface) within the ice draining preferentially to its northern flank.


Previous SiteNext Site

|Home|