Article: Population studies in the Ballyshannon Limestone, Ballina Limestone, and Rinn Point Beds (Viséan) of N.W. Ireland
Julia A. E. B. Hubbard
A numerical comparison of the populations of the outcrops formerly ascribed to the Ballyshannon Limestone and its lateral equivalents at Easky, Aughris, Serpent Rock, Streedagh, Kiln Port and Shalwy is presented. The localities define the limits of a subtrapezoidal area some 300 square miles in extent, in which the maximum distance between stations is 33 miles (Easky to Kiln Port) and the minimum 6-5 miles (Kiln Port to Shalwy). The four first named Sligo stations bear close similarities representing coral colonies, thickets, and even local coppices. The last two named Donegal stations have a different fauna which is not as dense and may be argued to represent either a different faunal province or, more probably, a different stratigraphical horizon. Aughrus (Co. Donegal), near the type area of the Ballyshannon Limestone, is alluded to. It shows a distinctive fauna with affinities to the other Donegal stations though proportionally the assemblage is unique.Stratigraphically the Donegal stations are regarded as belonging to the Ballyshannon Limestone (CtSx), while the Sligo stations are tentatively ascribed to the Benbulben Shale—Glencar Limestone (SJD,) transitional phase.Palaeoecologically all the faunas are regarded as having developed marginally between the dysphotic tropical belt and shallow warm waters of the open shelf. Of the Sligo stations Aughris is regarded as the most seaward facies of a coral biostrome. A niche biota faunal replacement of syringoporids by fasciculate lithostrotiontids, michelininiids by cerioid lithostrotiontids, narrow caniniids by giganteid forms, and davisiellids by linoproductids is postulated.