Palaeozoic Limestone Research Articles

Application of the GIS methods along with measured parameters to identify the NH4+ origin in the Hranice Karst (Czech Republic)

The study aims to determine the source of NH4+ ions in the mineral waters of the Hranice Karst. The study area is located in the eastern part of the Czech Republic, Europe. The area is known mainly for its carbon dioxide of deep origin; the gas was the factor that enabled the formation of hypogene karst, in the Palaeozoic limestones, as well as warm mineral waters. The limestones of the area are covered by Neogene (Miocene) sediments of variable thickness and lithology. Recurrent sampling was done at 36 sites. A total of 96 surface water samples, 65 borehole water samples and 96 karst water samples were assessed. Major anions, cations and the content of nitrogen and its forms were determined for all water samples. The soil types were characterised by a field pedological survey. The normalised difference vegetation index was calculated in QGIS and vegetation vitality was evaluated. Since places with remarkably low vegetation index were found to be linked to the occurrence of Miocene sandstones, they represent points of rather fast entry of rainwater into the ground. As the presence of carbon dioxide creates an anoxic setting underground, the entering nitrates are transformed into NH4+ ions. This mechanism of transformation within the nitrogen cycle explains the presence of NH4+ ions in areas with elevated CO2.

Transport Direction and Scandinavian Source Regions of the Saalian Glacial and Glaciofluvial Deposits in a Case Study of Łubienica-Superunki (Central Poland)

The article contains detailed petrographic studies, which covered a coarse and medium-grain gravel fraction of two layers of glacial till (units ŁS II and ŁS IV) and two layers of sand-gravelly outwash deposits (units ŁS I and ŁS III) related to the Odranian Glaciation (MIS6, Saalian) in Łubienica-Superunki, North Mazovian Lowland, central Poland. Additionally, the indicator erratics were identified to indicate their Scandinavian source areas and the directions of the ice sheet transgressions. This case study is discussed against the background of similar sediments and forms from the same age but from other places in the Polish Lowlands. Regardless of the facies types and fractions, crystalline rocks dominated over all other petrographic groups in all samples. The most common were the indicator erratics derived from the Åland Islands, followed by those from the south-eastern area of Sweden (Småland) and from Dalarna in central Sweden. Amongst the erratics of limited indicative significance, the most common were Lower Palaeozoic limestones and the Jotnian red sandstones. The complex petrographic analyses point to the dipartite nature of the studied profile. This separateness was confirmed by the TBC: 59.1–59.2° N and 18.0–18.2° E for the lower units and 58.8–59.4° N and 17.3–17.9° E for the upper ones.

Regional subglacial quarrying and abrasion below hard‐bedded palaeo‐ice streams crossing the Shield–Palaeozoic boundary of central Canada: the importance of substrate control

Three‐dimensional surface visualization models derived from high‐resolution LiDAR data provide new information about the type and scale of erosional processes below Late Wisconsin palaeo‐ice streams traversing the boundary between Canadian Shield crystalline rocks with offlapping Palaeozoic limestones in central Ontario. The hard bed is directly analogous to that found below ice streams in East Antarctica and East Greenland and provides insight into the effects of abrupt changes in substrate type on subglacial processes. Erosion of hard crystalline Canadian Shield rock was largely ineffectual consisting of areal abrasion of rounded whalebacks and local lee side plucking. In contrast, fast flow over the strike of gently dipping well‐bedded and jointed Palaeozoic limestones cut large flow‐parallel grooves and ridges akin to mega‐scale glacial lineations reflecting intense abrasion below narrow streams of subglacial debris dominated by hard crystalline Shield clasts (erodents). Regionally extensive plucking of structurally weak, well‐jointed and bedded limestone produced large volumes of rubbly carbonate debris leaving a 25‐km‐wide belt of uncontrolled hummocky rubble terrain (long known as the Dummer Moraine in Southern Ontario) some 350 km long and locally as much as 10 m thick. Subglacial plucking and abrasion under fast flowing ice were highly effective in stripping limestone cover rocks from Precambrian basement, and over many glacial cycles, may have played a role in the location and excavation of numerous large and deep lake basins around the Shield–Palaeozoic boundary zone in North America.

Integrative Paleobotany: Affirming the Role of Fossils in Modern Plant Biology—Introduction and Dedication

Integrative Paleobotany: Affirming the Role of Fossils in Modern Plant Biology—Introduction and Dedication

Early Permian (Cisuralian) ostracods from Japan: characteristic ostracod assemblage from a seamount of the Panthalassic Ocean.

Silicified ostracods were recovered from Cisuralian micritic limestones of the Ryozensan Limestone Formation from the southwestern part of Ryozensan Mountain, Taga City located in Shiga Prefecture, Central Japan. Twenty-seven species belonging to 19 genera were obtained, of which six species are new and are described here: Bairdia tagaensis Tanaka sp. nov., Bairdiacypris ikeyanoriyukii Tanaka sp. nov., Kellettina noriyukii Tanaka sp. nov., Microcheilinella shigensis Tanaka sp. nov., Oliganisus ryozensannensis Tanaka sp. nov., and Pustulobairdia ohmiensis Tanaka sp. nov. Some Palaeozoic limestone localities in Japan cap greenstones and are surrounded by younger cherts (such as Mino Terrane of this study). They represent a characteristic reef and reef-slope environment around a seamount surrounded by deep sea ocean floor. This result is concordant with the ostracod assemblage. After this report, a Panthalassan ostracod fauna could be defined for the Cisuralian.

Compositional characteristics and experimental burning of selected Lower Palaeozoic limestones from the Prague Basin (Barrandian area, Czech Republic) suitable for the production of natural hydraulic lime

Laboratory-scale experimental burning of three facial types of Devonian limestones from the Barrandian area (Czech Republic) revealed their suitability for production of natural hydraulic lime and/or natural cement of variable degrees of hydraulicity. Although employed as a raw material for ordinary Portland cement at present, all these limestones must be blended to achieve the optimum composition required for ordinary Portland cement clinker. However, if burnt in their natural state (i.e. without any further addition of SiO2, Al2O3 and/or Fe2O3), and by using a sufficiently coarse grained batch, they exhibit favourable content of newly formed hydraulic phases. These are controlled not only by overall mineralogical/chemical composition of a raw material, but also by burning conditions, specifically by peak temperature and its duration. Prevalent dicalcium silicate (larnite) plus some minor calcium aluminosilicates (gehlenite) or aluminoferrites (brownmillerite) form due to solid state reactions between homogeneously distributed non-carbonate fraction (silica minerals, clay minerals, feldspars) in micritic carbonate groundmass.

Aspects of geodiversity of Palaeozoic limestones in the Black Mountains of southern France

In the southern Massif Central (France), where the scenery resembles that of Middle-earth, the geodiversity of carbonate formations (limestones and dolomites), mainly of Paleozoic age, can be observed in the nested scales of the geotopes, geofacies, and geosystems.

Petrographical Analysis of Warthian Fuvioglacial Gravels as a Tool to Trace the Source Area – A Case Study From Central Poland

Abstract The petrographical features of the medium- and coarse-grained gravels (4-10 mm and 20-60 mm, respectively) of weathered and fresh (unweathered) deposits indicate, in combination with so-called indicator and statistical erratics, that two glacial lobes joined in the borderland of the Polish Lowlands and Uplands. Lower Palaeozoic limestones become less frequent in the fner gravel fraction, whereas crystalline rocks and fints become more frequent. The petrographical analysis of the coarser gravel fraction indicates that the ice sheet advanced from the NE to NNW (the Widawka lobe) and from the NE to ENE (the Rawka, Pilica and Luciąża lobes). The source areas of the gravel deposited by the Warthian ice sheet were magmatic and sedimentary areas of both the Baltic and the SE Sweden basins.

Characterization of the Sündikendağı deposit of moganite-rich, blue chalcedony nodules, Mayıslar–Sarıcakaya (Eskişehir), Turkey

Blue chalcedony nodules have been mined from the Sündikendağı deposit in the Mayıslar–Sarıcakaya (Eskişehir) region of north-central Turkey since ancient times; however, no modern geological study of this deposit has yet been published. Although ancient and current mining production have both taken place in an area of complex geology, our study and analyses of the deposit suggests a simple model of sedimentary deposition for its origin. The repeated episodes of tectonic activity, accompanied by brittle deformation, metamorphism, and hydrothermal activity, which characterize this part of the Anatolian Peninsula with its complex junction of tectonic plates, appear to have had little influence on the blue chalcedony nodules that make the deposit valuable other than perhaps to influence their trace-element composition.The physical nature of the nodules as revealed by polarized-light microscopy and XRD—they are composed only of fibrous length-fast quartz (chalcedony) and fibrous length-slow quartz (moganite), but contain neither platy opal-CT nor opal-C—is consistent with a sedimentary origin as are their overall shape and strata-bound occurrence in a sandstone (arkose).The relatively high concentrations of some trace elements in the nodules revealed by ICP-AES, suggest involvement of hydrothermal fluids during the direct epigenetic formation of chalcedony concretions during diagenesis of the enclosing sandstone or by alteration of diagenetic concretions of another composition. Sources could include upwardly moving hydrothermal fluids entering the sedimentary basin from underlying older Sarıcakaya intrusive rocks or sea-floor hydrothermal vents in the vicinity during diagenesis in the Palaeocene and Eocene (65–37.8Ma) periods.Oxygen isotope analyses (SMOW) (using EA-IRMS) of both the blue chalcedony nodules (δ18O=+28.2‰ to +30.8‰) and the enclosing sandstone (δ18O=+11.3‰ to +13.2‰) suggest that the nodules formed during diagenesis at a low temperature of around 55°C, although they are encased in sandstone whose grains came from rocks that formed at significantly higher temperature, perhaps above 100°C.The unbanded Sündikendağı chalcedony nodules are similar in occurrence to the banded Fairburn agates of South Dakota, USA and the Dryhead agates of Montana, USA, which formed in Palaeozoic limestones, except that the blue chalcedony is hosted in sandstone. Other sedimentary agates are generally believed to have formed by the alteration of diagenetic concretions from the outside, inward. No other agates or chalcedonies hosted in sandstone are known for comparison with this deposit. Thus, the deposit appears to be unique. It is possible that the Sündikendağı unbanded blue chalcedony formed as epigenetic concretions during diagenesis of the sandstone—a mechanism previously shown for large crystals of other minerals found in sandstones.

Pre-industrial headstones across the continental North Sea plain

This paper examines the spatial and temporal distribution of grave headstones in the relatively homogeneous North Sea plain and adjacent regions during the seventeenth and eighteenth centuries, as well as the various lithological, cultural, religious and transportation factors influencing this distribution. Findings from close inspection of cemeteries across the study area were complemented with data from existing surveys. The larger part of the production of headstones was for local consumption. High densities of cruciform (Catholic) headstones in the Boulonnais and in most of the Ardennes–Rhenish massif are illustrated with the cases of the Berwinne and Vesdre headstone production workshops. Beyond concentrations along the Meuse and Rhine rivers, there is a large area stretching from northern France to north-west Germany in which no headstones can be found (with the notable exception of a few Jewish cemeteries). Beyond this area devoid of headstones, the Marsh Islands and adjacent continental areas again have high densities (more than 1 headstone per km 2), occurring in two well-differentiated clusters. One cluster contains simple poles in Belgian Palaeozoic limestone in North-Holland and the West-Frisian islands, and the other cluster, on the German and Danish Marsh Islands, holds richly decorated tablets made in sandstone from the Weserbergland. The headstones on the Marsh Islands, a unifying cultural element in this UNESCO world heritage area, bear witness to the significance of a lucrative whaling activity and the intense trade that developed despite political, religious and linguistic differences across the region.

Petrology and petrogenesis of carbonatitic rocks in syenites from central Anatolia, Turkey

The late Cretaceous A-type Karacayir pluton in Central Anatolia, Turkey, intrudes and entrains xenoliths of Palaeozoic limestone. Carbonatitic magmatic rocks within the syenite have been previously interpreted (Schuiling in Nature, 192:1280, 1961) to result from metasomatic alteration and syntectic melting of marble. Carbonatites and associated calcite-syenites exhibit mineralogical characteristics (Ab-rich plagioclase, Ba-rich K-feldspar, low-Mg# biotite) that are petrogenetically more evolved than the host syenitic suite. Geochemically, carbonate-rich magmatic rocks are greatly enriched in Sr, Ba, Th, and REE and have higher LREE/HREE ratios than either syenites or marbles. In terms of O-C-Sr-Pb isotope ratios, the carbonatite/calcite-syenite suite form a consistent and geochemically coherent group that is distinct from the marble country rock and xenolith population, but similar to some of the syenitic, and particularly the nepheline syenite components of the Karacayir pluton. Other silicate magmatic rocks are geochemically, isotopically, and geochronologically different, suggesting the pluton is composite. Overall, the mineralogical and geochemical characteristics of the carbonatites are incompatible with binary mixing of syenite and marble but are consistent with derivation of carbonatite from petrogenetically evolved foid syenite. Carbonate–silicate rock types have modal variations compatible with an origin by fractional crystallisation, rather than by liquid immiscibility.

Rethinking eastern Australian caves

Abstract There are some 300 bodies of cavernous limestone in eastern Australia, extending from Precipitous Bluff in southeastern Tasmania to the Mitchell Palmer region in north Queensland. These impounded karsts, developed in Palaeozoic limestones of the Tasman Fold Belt System, contain many caves. The caves have a suite of features in common that allows them to be thought of as a major group: the Tasmanic Caves. The Tasmanic Caves include multiphase hypogene caves such as Cathedral Cave at Wellington and multiphase, multiprocess caves such as Jenolan with Carboniferous hypogene and younger paragenetic and fluvial elements. Active hypogene caves occur at Wee Jasper and possibly at five other localities. The Tasmanic Caves are one of the most complex suites of caves in folded Palaeozoic limestones in the world. Field techniques developed to study these caves are now being applied to complex caves in central Europe: in the Czech Republic, Hungary, Poland, Slovakia and Slovenia.

Evidence of multiple late Bashkirian to early Moscovian (Pennsylvanian) fire events preserved in contemporaneous cave fills

During a low sea level stand and wet climate phase at the end of the Mississippian, Lower Palaeozoic limestones at the northern edge of the Illinois Basin were karstified. The caves and fissures that formed were infilled subsequently with clastic sediments of Pennsylvanian age (late Bashkirian–early Moscovian (= Atokan, Duckmantian/Bolsovian, Westphalian B/C)). The earliest infills comprise organic-rich, almost coaly, sediments, while sands, silts and fine clays were deposited subsequently. The sediments are fossiliferous and contain abundant plant fragments, most notably cordaitalean and conifer remains. Many of the plants and megaspores are uncompressed and have undergone minimal thermal alteration. Charcoal occurs throughout the sedimentary infills but is most abundant in the later deposits, where conifer remains predominate. These conifers are currently amongst the oldest known from North America. The presence of cordaitalean remains in the earliest coaly infills is supported by the detection of specific fernane derivatives. The lipid extract of the cave fill sequence contains polyaromatic hydrocarbons (PAHs), such as pyrene, chrysene, benzo[ghi]perylene, and coronene, which distribution further attests to the importance of wildfire in preserving the plant remains.

The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland

Ultrabasic alkaline magmatic rocks are products of melts generated deep within or at the base of the lithospheric mantle. The magmas may reach the surface to form lavas and pyroclastic deposits; alternatively they crystallise at depth to form dykes or central complexes. The rocks are chemically distinct and may contain high concentrations of economically interesting minerals and chemical elements, such as diamonds, niobium, tantalum, rare earth elements, phosphorus, iron, uranium, thorium, and zirconium. Ultrabasic alkaline rocks are known from several provinces in Greenland, but extrusive facies have only been preserved at a few places; e.g. at Qassiarsuk in South Greenland where pyroclastic rocks occur, and in the Maniitsoq region, where a small volcanic breccia (‘Fossilik’) contains fragments of Palaeozoic limestone. Ultramafic lamprophyre and kimberlite are mainly emplaced as dykes, whereas carbonatite forms large intrusive bodies as well as dykes. The ultrabasic alkaline magmas that have been emplaced at certain times during the geological evolution of Greenland can be related to major episodes of continental break-up (Larsen & Rex 1992). The oldest are Archaean and the youngest dated so far are Palaeogene. Figure 1 shows the distribution of known ultrabasic alkaline rocks in West Greenland. The large and well-exposed bodies of alkaline rocks and carbonatites in the Gardar Province were discovered already in the early 1800s (Ussing 1912), while less conspicuous bodies were discovered much later during geological mapping and mineral exploration. Many alkaline rock bodies, particularly dykes, are difficult to identify in the field because they weather more extensively than the country rock gneisses and form vegetated depressions in the landscape. However, their distinct chemistry and mineralogy render alkaline rocks identifiable in geochemical and geophysical survey data. Thus, the Sarfartôq carbonatite complex was discovered during regional airborne gamma-spectrometric surveying owing to its elevated uranium and thorium contents (Secher 1986). The use of kimberlite indicator minerals has led to the discovery of alkaline rocks such as kimberlites and ultramafic lamprophyres that carry fragments of deep lithospheric mantle. Such rocks may also contain diamonds. Kimberlite indicator minerals are high-pressure varieties of minerals, such as garnet, clinopyroxene, chromite and ilmenite that were formed in the lithospheric mantle. Exploration companies have processed thousands of till samples from southern West Greenland for kimberlite indicator minerals and found many new dykes.

Variscan veins: record of fluid circulation and Variscan tectonothermal events in Upper Palaeozoic limestones of the Moravian Karst, Czech Republic

Numerous Variscan syntectonic calcite veins cross-cut Palaeozoic rocks in the Moravian Karst. A structural, petrographic and stable isotopic analysis of the calcite veins and a microthermometric study of fluid inclusions in these vein cements have been carried out to determine the origin of the Variscan fluids and their migration during burial and deformation. The isotopic parameters of white (older, more deformed) and rose (younger) calcites are: 87Sr/86Sr is between 0.7078 and 0.7082 (white) and 0.7086 (rose), δ18O is between +17.7 and +26.1 (white) and between +14.8 and +20.7 ‰ SMOW (rose), δ13C ranges from +0.1 to +2.5 (white) and from −0.3 to +1.6 ‰ V-PDB (rose). The isotopic signatures point to precipitation in an older fluid system buffered by the host rock (white calcites) and to an open, younger fluid-dominated system (rose calcites). Parent fluids (H2O–NaCl system) had salinities between 0.35 and 17.25 eq. wt % NaCl. The pressure-corrected and confined homogenization temperatures suggest formation of the calcite veins from a fluid with a temperature between 120 and 170 °C, a pressure of 300–880 bar at a depth between 2.1 and 3.2 km. The fluids were most likely confined to a particular sedimentary bed as a bed-scale fluid migration (white older calcite veins) or, later, to a pile of Palaeozoic sediments as a stratigraphically restricted fluid flow (rose younger calcite veins). The low temperatures and pressures during precipitation of calcites, which took place close to a peak of burial/deformation, confirm the distal position of the Moravian Karst region within the Variscan orogen.

Allochthonous sediment in till near a lithological boundary in central Ontario

Clast counts, and measurements of carbonate abundance in the sand fraction, show that little of the till covering a portion of central Ontario was carried across the boundary between Precambrian rocks (up-ice) and Palaeozoic limestone (downice). Seven eighths of the pebble fraction is local, from within ~2-5 km of the site of deposition. The distantly-derived component becomes gradually less abundant down-ice from the lithological boundary, with an exponential distance scale of about 30 km. We ascribe this gradual loss to a combination of comminution and depletion by deposition.However it is not possible to map variations in the abundance of erratics; the pattern is spatially homogeneous and random. The same is true of the abundance of insoluble sand which, moreover, is highly variable.The role of transport of allochthonous sand from the Shield cannot be separated from those of comminution, erosion of local bedrock, postglacial alteration and inheritance of pre-glacial material. The till is best understood as an intimate mixture of "frictional gouge", still more or less in situ , and englacially-transported sediment. Thus it is neither lodgement till nor meltout till; it may be a deformation till, but if so the episode of deformation can have lasted only a few hundred years

A 340,000 year record of ice rafting, palaeoclimatic fluctuations, and shelf-crossing glacial advances in the southwestern Labrador Sea

Orphan Basin, southwestern Labrador Sea, is a strategic site for the study of Quaternary palaeoceanography and palaeoclimate. A 31.45-m-long piston core (MD95-2025) was raised from 2925-m-depth at 49°47.645′N, 46°41.851′W, just beyond the seaward limit of stacked debris-flow tongues derived from the Northeast Newfoundland Shelf. The core extends to oxygen isotopic stage 9 (∼340,000 years), and includes 13 prominent ice-rafted layers (Heinrich events H1–H13), many of which are characterized by abundant detrital Palaeozoic limestone and dolomite. Warm peaks in sea-surface temperature (SST) show poor correlation with accentuated ice rafting, except for 20–60 ka (H3–H5) when the terminations of meltwater pulses ( δ 18O minima) lagged warm peaks in SST by ∼1000 years, and peaks in ice rafting either coincided with peaks in SST (H4, H5), or lagged warmer peaks in SST by ∼500 years (H3). These lags are attributed to the delayed response of ice sheets (e.g., iceberg and meltwater production rates) to palaeoceanographic and palaeoclimatic forcing factors (e.g., incursions of the warm North Atlantic Drift into the Labrador Sea; orbital-induced changes in insolation). The remarkable covariance between SST and ice rafting from 20–60 ka is inconsistent with models for ice-stream surging through Hudson Strait [Marshall, S.J. and G.K.C. Clarke, 1997. A continuum mixture model of ice stream thermomechanics in the Laurentide Ice Sheet 2: application to the Hudson Strait ice stream. J. Geophys. Res., B102, 20615–20637], and instead suggests that regional changes in ocean circulation played an important role in destabilizing icesheets. Heinrich layers H1, H3–H6, H9, H11, and H13 formed during times of sharply decreasing δ 18O values (i.e., ice sheet melting). Heinrich layers H2, H7 and H12 formed at transitions from interglacial/interstadial to glacial stages, coincident with both cool SST and low fluxes of detrital carbonate. They may represent the initiation of calving as growing ice sheets readvanced to coastal areas of the Labrador Sea and Baffin Bay. Carbonate-poor H8 and H10 developed during interglacial stages 5 and 7, and may have been derived mainly from Greenland like the modern ice-rafted sediments of the Labrador Sea.

A pleistocene frost-heaved dome in palaeozoic limestone at Kingston, Ontario, Canada

A dome in Palaeozoic limestone at Kingston is 7.5 m in diameter as revealed in a roadcut and about 11 m at its maximum as indicated by ground-penetrating radar. The centre has been displaced 1.5 m upward in the exposure and up to 2.5 m internally in a circular arch. The dome appears to be roughly circular in plan and up-arching of the limestone extends to about 17 m depth. The dome has been eroded to a nearly plane surface by glaciation as indicated by striations on limestone blocks at the surface. Based on similarity of form to features in modern periglacial environments, the dome is proposed to have originated by frost heaving of bedrock before the late Wisconsinan glaciation of southern Ontario. This is the first report of such a feature, and recognition of their occurrence in formerly periglacial regimes should provide a useful tool in palaeoenvironmental reconstruction. Copyright © 2000 John Wiley & Sons, Ltd. Un dome developpe dans des calcaires plaeozoiques a ete observe lors de l'excavation d'une tranchee a Kingston. Le diametre de la forme telle qu'elle est apparue dans la tranchee, est de 7.5 m; a son maximum, il atteindrait 11 m selon une prospection radar. Le soulevement visible dans la tranchee est de 1.5 m, mais le soulevement maximum serait de plus de 2.5 m formerait ainsi une arche. Le dome est approximativement circulaire en plan et le soulevement s'etend jusqu'a une profondeur d'environ 17 m. Le dome a ete rabote par un glacier jusqu'a une surface presque plane en laissant des stries en surface sur les blocs de calcaire. Etant donne la similitude de forme avec des phenomenes connus actuellement dans les environnements periglaciaires actuels, ce dome est interprete comme resultant d'un soulevement par le gel du bedrock, soulevement anterieur a la derniere phase glaciaire qui a recouvert l'Ontario meridional. Le present article est la premiere description d'un phenomene periglaciaire fossile de ce type. La reconnaissance de phenomenes semblables pourrait fournir un outil utile pour des reconstructions paleoenvironnementales. Copyright © 2000 John Wiley & Sons, Ltd.

Recognition and implications of Eocene tufas and travertines in the Chadron Formation, White River Group, Badlands of South Dakota

There are few descriptions of pre‐Quaternary tufa or travertine, yet these deposits have important climatic, hydrological and tectonic implications. In the Badlands of South Dakota, the Late Eocene Chadron Formation contains a variety of tufa (fluvial, lacustrine, paludal and perched springline types), travertine and calcrete (pedogenic and non‐pedogenic types). In fluvial channels, tufas and tufa barrages (oncolites, tufa lithoclast conglomerates and phytoherms) are transitional to travertines (pseudostromatolitic boundstone gravels and small pinnacle resurgences with rimstone edges and pools). Lacustrine tufas formed in small ponds adjacent to other types of tufas and are similar to the ‘low‐energy, bench‐margin facies’ types observed in modern, groundwater‐fed, temperate‐zone hardwater lakes. Paludal tufas are laterally discontinuous sheets of pisoid‐intraclast wackestone that fill palaeotopography. Distal perched springline tufas are mounds of numerous sloping tufa sheets. Concretions and rhizoliths associated with palaeosols are recognized as pedogenic calcretes, whereas non‐pedogenic calcretes are variably cemented, vertically oriented conduits for palaeogroundwater discharge that are located in fault zones. These deposits resulted from palaeogroundwater discharge along faults during the Late Eocene. Coeval unroofing of the Black Hills uplift created a regional groundwater flow system through karsted Palaeozoic limestones exposed in the Black Hills. The Chadron Formation is an avulsion‐dominated, siliciclastic unit, yet important bodies of carbonate accumulated in it as a result of groundwater processes.

An improved technique for extracting calcareous microfossils from Palaeozoic limestones

Well preserved calcareous microfossils, such as ostracods, can be extracted from strongly lithified Palaeozoic limestones of the Lachlan Fold Belt using highly concentrated acetic acid (95%) with minimal dissociation. This technique differs from the more dilute acetic acid or formic acid methods which are commonly used during the extraction of phosphatic microfossils, such as conodonts, and which destroy many calcitic specimens. Correlations made between representative microfossil assemblages and host rock thin sections expand knowledge of palaeoenvironmental parameters attributed to microfacies.