|Tilted blocks of chalk on the west side of White Park Bay, Co.Antrim, showing successive chalk members: Galboly Chalk, Cloghastucan Chalk (with Oweynamuck Flint Band clearly visible) and Creggan Chalk.|
|Site Type: ||Coastal section|
|Site Status: ||ASSI, PASSI|
|District: ||Moyle District Council|
|Grid Reference: ||D008443, D029449|
|Rock Age: ||Cretaceous, Jurassic (Campanian, Cenomanian, Lower Jurassic, Santonian)|
|Rock Name: ||Ballintoy Chalk Member, Ballymagarry Chalk Member, Boheeshane Chalk Member, Cloghastucan Chalk Member, Creggan Chalk Member, Galboly Chalk Member, Garron Chalk Member, Glenarm Chalk Member, Hibernian Greensands Formation, Larry Bane Chalk Member, Portrush|
|Rock Type: ||Conglomerate, Flint, Limestone, Mudstone|
|Fossil Groups: ||Ammonite, Bivalve, Brachiopod, Gastropod|
|Other interest: ||No data, Marine sediments|
Summary of site:
The near perfect sweep of White Park Bay, framed between the gleaming limestone portals of Dundriff in the east and Portbradden in the west, backed by over 2 km of dunes behind a crescent beach, has drawn interest from the earliest human colonisation of Ireland. Its archaeological, biological and geological riches were a magnet to the scientifically curious from the early years of the 19th century and it became a rich collecting ground for organisations such as the Belfast Natural History and Philosophical Society, the Belfast Naturalistsí Field Club and a continuing pilgrimage of eager amateurs and professionals.
Its geological time span is limited to parts of the Jurassic and Cretaceous periods but the events they recount are both complex and important.
The first half of the Jurassic period, the Lower Jurassic, more commonly known as the Liassic or Lias is represented by rocks in several parts of the bay. At the eastern end, forming the toes of a series of landslips, Liassic rocks are seen beneath the Ulster White Limestone. These rocks, the Waterloo Mudstone Formation are grey, glutinous muds for the most part with lime-rich silts and bands of limestone nodules. A rich and varied fauna has been collected from them with many species of the flat-spiralled ammonites, a group that evolved rapidly consequently providing a reliable framework for the relative dating of the rocks. The earliest forms indicated the bucklandi Zone, the latest the jamesoni Zone, a time span of over 10 million years between 205 and 195 million years ago. Following winter storms when sand has been stripped from the beach, large expanses of Liassic mudstones can be seen along the shore.
Above the Lias there is a concentration of brown, shiny, phosphatized pebbles in a green chalky limestone coloured by grains of the mineral glauconite. This conglomerate marks the base of the local Cretaceous rocks and includes debris from the Waterloo Mudstone, including Liassic fossils. At the east end of the bay it grades upwards into 3 members of the Ulster White Limestone succession, the Galboly, Cloghastucan and Creggan Chalk Members, the top of the last recognised by the Bendoo Pebble Bed. At the west end a further 7 members are present from the Boheeshane Chalk to the Ballymagarry Chalk. The fossils in this succession span a 10 million year period from roughly 84 to 74 million yeas ago, towards the end of the Cretaceous period.
A compilation of historic faunal lists shows that in the past, ammonites were collected from the lowest Liassic zone, the planorbis Zone up to the davoei Zone, one above the last zone observable now. This is perfectly possible: in the early days, the Belfast Natural History and Philosophical Society used to employ labourers to clean the sections in the gullies at the back of the beach in preparation for collecting excursions. This gave fuller successions than those naturally exposed at the present time.
The basal conglomerate of the Cretaceous is shown on the modern geological map as the Hibernian Greensand but in the bay it is a mere remnant of the period starting 10 million years earlier when the greensands dominated. Globular, heart-shaped sea urchins collected from Oweynamuck at the east end of the bay suggest that it belongs to the coranguinum Zone, part of the Coniacian stage, dating to around 88 million years ago.
The time interval between the last Liassic rocks and the earliest Cretaceous rocks seen in White Park Bay is over 100 million years and it is likely that the area was dry land for a substantial part of that period. This coincides with the acme of the Age of the Dinosaurs conjuring possibilities that remain speculative in the absence of land deposits.
This interesting range of rocks and their rich fossil faunas, not to mention the equally interesting breaks of sequence, in this imposing setting make this a nationally important area that should be designated for its scientific and aesthetic importance.
The rich faunas from these localities are strongly represented in the collections of the Ulster Museum.