Waulsortian Limestones Research Articles

Biogenic and non-biogenic concentration of sulphur and metals in the carbonate-hosted ballinalack Zn-Pb deposit, Ireland

The Zn-Pb deposit of Ballinalack, Ireland, is hosted within a stomatactis cavity system in the Waulsortian Limestones. Earlier sulphides contain fossil bacteria suggesting a direct bacterial reduction of sulphur at the place of the mineralization. Later sulphides contain relics of thiosulphates and sulphites suggesting abiotic sulphur reduction. Part of the metals was temporarily introduced into the carbonates, which subsequently have been heavily replaced by sulphides. Sulphur was derived from the sea-water and metals from a deep-seated source. To explain the mineralization two separate convection cells are proposed: shallow cold with sulphur and deep hot with metals. Fluids derived from these two cells were subjected to dynamic mixing within a highly permeable stromatactis cavity system. To study small relics of thiosulphates and sulphites, sulphur valence was measured by microprobe. The method is based on the valence related shift of the SKα and SKs lines measured with microprobe spectrometers.

Facies variations within the Waulsortian Limestone Formation of the Dungarvan Syncline, southern Ireland

A number of facies can be recognised within the Waulsortian Limestone Formation of the Dungarvan Syncline. Bryozoan ‘reefs’ are common, but mottled, shale-wisped and homogeneous calcilutites comprise the bulk of the formation. Crinoidal limestones, banded and cherty calcilutites are minor components. The bryozoan ‘reefs’ developed in deep water, but with decreasing water depth the production and sedimentation of micrite increased, eventually smothering the bryozoans, resulting in mottled and homogeneous calcilutites. The presence of bryozoan ‘reefs’ at higher levels suggests that the sea-level was fluctuating with bryozoan recolonization occurring after increases in water depth. The crinoidal facies represents dense crinoid colonies which acted as localized sediment baffles. Shale-wisped calcilutites are most common at or close to the base of the Waulsortian, where background shale deposition was significant. However at higher levels the increased carbonate production had a diluting effect. These facies have been related to the phases of Lees, Hallet & Hibo (1985). The bryozoan ‘reefs’ are considered to represent Phase A, while mottled calcilutites can be related to Phases B and C. The homogeneous calcilutites which display evidence of intense algal activity represent Phase D.

The Courceyan stratigraphy of the Pallaskenry Borehole, County Limerick, Ireland

AbstractThe Pallaskenry Borehole, Co. Limerick, Ireland provides an almost complete Courceyan (Dinantian) succession from Old Red Sandstone facies up to Waulsortian limestones. A revised lithostratigraphic‐al nomenclature for this succession is presented. Examination of the conodont and coral faunas in the borehole has enabled biozones to be defined which can be recognized throughout the Limerick Province. Biostratigraphical correlations are made with Courceyan successions at Hook Head, Co. Wexford, in the Mendip Hills and in Knap Farm Borehole in the Southwestern Province of Britain. Conodont taxa show a clear distinction betweeen the shelf faunas of the Limerick Province, Hook Head and eastern Mendip, and distal shelf faunas from south Cork, Knap Farm and Dinant, Belgium, which probably reflect their different palaeogeographical positions.Acknowledgements. The authors wish to express their thanks to Professor G. D. Sevastopulo, Drs. R. L. Austin, J. R. Nudds and P. Strogen and Mr. M. Mitchell for constructive criticism of the manuscript. We would also like to thank Dr. T. R. Reilly, Mr. C. McDermot and Dr. A. Sleeman of the Geological Survey of Ireland, and Dr. M. E. Philcox for fruitful discussion on the Iithostratig‐raphical nomenclature. G. LI. Jones was a Research Fellow at Trinity College, Dublin during the period of this work. He was funded through the Upper Palaeozoic Atlas of Ireland (UPAIR) Project, financed by the Department of Energy and administered through the Geological Survey of Ireland and Trinity College. He gratefully acknowledges the organization and supervision provided by Professors C. H. Holland and G. D. Sevastopulo and Dr. D. Naylor; and the assistance with conodont processing given by Ms. B. Thornbury. Thanks are also extended to Mr. J. Kennedy and Mr. P. Moffat for assistance with the diagrams.

Regional Cement Stratigraphy and Diagenetic History of Waulsortian Limestones, Eastern Midlands, Republic of Ireland: ABSTRACT

The Lower Carboniferous Waulsortian Limestones, eastern Midlands, Republic of Ireland, contain 7 distinct luminescent zones in clear calcite cements that overlie inclusion-rich, marine cements in cavities and also fill fractures and aragonite-skeleton molds. The luminescent sequence, which records precipitation from increasingly reducing pore waters, is regionally and stratigraphically consistent over an interval more than 1,200 ft thick. Zone 1 cements are nonluminescent; zone 2 cements are brightly luminescent; and zones 3-7 cements are ferroan with a moderate to dull luminescence. Zone 1 cements (mean -2.6% ^dgr18O/+3.3% ^dgr13C PDB) are slightly depleted in oxygen relative to radiaxial-fibrous cements (mean -1.8%^dgr18O/+3.5%^dgr1 C PDB) which have a composition that reflects Lower Carboniferous seawater. Zone 4 cements (mean -4.1%^dgr18O/+3.1%^dgr13C PDB) are depleted in oxygen relative to zone 1, whereas zone 5 cements (mean -11.8%^dgr18O/+1.1^dgr13C PDB) are extremely depleted in oxygen and somewhat in carbon. Locally intense dolomitization includes 2 regionally extensive generations of ferroan saddle dolomite. Petrographic relationships demonstrate these dolomite generations were replaced by zone 5 cement. Sulfide mineralization, principally pyrite and sphalerite, occurred after the precipitation of zone 5 cement. Much of diagenesis occurred during a brief period in the Lower Carboniferous. Zones 1-6 and saddle dolomites are contained in Chadian (upper Osagean), shallow-marine facies overlying the Waulsortian. Fractures filled by zone 5 cements are truncated at the margins of Waulsortian clasts contained in a conglomerate overlying an early Arundian (early Meramecian) unconformity. In the proposed model, marine pore waters were displaced by oxidizing meteoric waters, which became reducing with shallow burial. Warm brines were introduced during later stages of diagenesis and were involved in late calcite cementation (zone 4?-7), saddle dolomitization and sulfide mineralization. End_of_Article - Last_Page 273------------

The structure and origin of the Waulsortian (Lower Carboniferous) “reefs” of west-central Eire

The structure and origin of the Waulsortian (Lower Carboniferous) “reefs” of west-central Eire

Stratigraphy and Origin of the Cork Red Marble

AbstractThe Cork Red Marble is a coarse, graded but poorly sorted, re-sedimented lime-conglomerate, of Caninian age. It occupies a central position within 4,000 feet of Waulsortian limestones. The pebble content of “porcellanous” calcite mudstone—not in reef facies—is set in a matrix of red clay. Mixed biofacies are represented, because of reworking: fragmented large molluscs, indicative of a nourishing reef habitat, contrast forcibly with a mollusc spat-ostracod assemblage as found in the pebbles. The conglomerate was probably formed when back-reef sediments, which included red clay, were elevated and then redeposited, possibly by turbidity currents

The Waulsortian "Reefs" of Eire: A Carbonate Mudbank Complex of Lower Carboniferous Age

The main features of the Waulsortian (Upper Tournaisian and Lower Vise'an) carbonate mudbank complex of Eire are described and the paleogeography outlined. The distribution and lithological characters of the Waulsortian limestones and associated sediments are briefly described. The Waulsortian rocks comprise a large mudbank complex, together with numerous discontinuous banks which formed in the lagoon on the landward side of the complex. The complex originally extended over an area of about 7,000 square miles in Eire. Thickness variations are shown on an isopach map. The development of the complex was controlled by two (or more) stable structural blocks on the Variscan foreland. These allowed the accumulation of a great thickness of Waulsortian limestone in the Shannon (NW. Co. Limerick and S. Co. Clare) and Cork areas before lateral spreading began. Bank growth took two main forms. These, the knoll and sheet forms, are briefly described and illustrated. The mechanism of growth is less certain. It is sugg...