The Ballynoe barite deposit is a conformable, mineralized horizon of Lower Carboniferous age overlying a diastem and mass faunal extinction demarking the transition from a quiet water environment to one of dynamic sedimentation. The geometry of the barite orebody correlates with the palaeo-topography of the footwall, which acted as an important control over the lateral extent, thickness and nature of the mineralization. Sedimentary features within the barite horizon suggest that it was precipitated in the form of a cryptocrystalline mud which underwent major diagenetic modification resulting in extensive stylolitisation, recrystallisation and remobilization. There is abundant and compelling geological and isotopic evidence for early local exhalation from the presence of a hydrothermal vent fauna consisting of a delicately pyritized worm tubes hosted and haematized filaments of apparent microbial origin. The worm tubes are remarkably similar to examples from modern and ancient volcanic-hosted massive sulphide deposits, and the filamentous microfossils have similarities to modern Fe-oxidizing bacteria. Strontium in the barite has a 87Sr/86Sr ratio indistinguishable from sea-water between 350 and 344Ma whilst oxygen isotopes from barite and chert suggest a diagenetic origin in equilibrium such sea-water around 60-70°C. Fluid inclusion studies have shown that, in general, low temperature inclusions are very saline (20-25%) whilst at higher homogenization temperatures they are more dilute (9-12%).

Variations in geochemical signatures of fossil brachiopod shells may be due to diagenesis and/or biological processes (i.e. ‘vital effects’). Characterize them is crucial to identify reliable areas into the shell suitable to paleoclimatological studies. This investigation contributes to an in-depth understanding of geochemical variations of Gigantoproductus sp. shells (SW Spain, Serpukhovian age), which could affect to the Late Paleozoic Ice Age interpretation. Microstructural, crystallographic, cathodoluminescence and geochemical (minor and trace elements, δ18O, δ13C, and strontium isotopes) characterisation have been performed on the tertiary layer of the ventral valve, to assess the preservation state. Poorly-preserved areas exhibit microstructural and geochemical changes such as recrystallisation, fracturing and higher Mn and Fe enrichment. Moreover, these areas have higher dispersion of ⁸⁶Sr, ⁸⁷Sr, δ18O and δ13C than well-preserved areas. Three structural regions have been identified in well-preserved areas of ventral valve by differences in valve curvature and thickness, such as the umbonal, thick and thin regions. These regions have different proportions of Mg, S, Na, δ18O, and δ13C, whom are interpreted as ‘vital effects’ and probably are related with growth rate differences during shell growth. Gigantoproductus tertiary layer seems the best suitable to paleoclimatological studies because it retains the original microstructure and geochemistry.

Silicified ostracods from the Lower Carboniferous (Lower Tin Mountain Limestone; Kinderhookian-early Osagean; 350-358.9 Ma) of Lost Burro Gap, Death Valley region, Inyo County, California, USA augment the diversity of Paleozoic ostracods of western North America. Acid maceration of pelmatozoan, micritic and silicate clay-rich micritic marine limestones yielded the following palaeocopid and podocopid ostracods: Acratia spp., Bairdia quasilecta Bushmina, 1975, Bairdia sp. cf. B. orientalis, Ceratobairdia sp., Kirkbya panamintensis sp. nov., Rectobairdia sp. cf. R. legumen, and Silenites sp. This is the first report of Ceratobairdia and Silenites from the Tin Mountain Limestone. These ostracods occupied a Panthalassan carbonate ramp environment, and represent part of a fauna that was widespread in shallow marine waters of Panthalassa.

Mesozoic-Palaeozoic marine carbonate rocks are important hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin (SYSB). Due to the lack of boreholes and the great heterogeneity of carbonate reservoirs, the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear. Based on seismic inversion and isotope analysis, this study explores the factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB. In this study, the log-seismic characteristics of porous carbonate reservoirs, sensitive lithology parameters, and physical property parameters are extracted and analyzed. The pre-stack simultaneous inversion technique is applied to predict the lithology properties and physical properties of the porous carbonate reservoirs. Moreover, the sedimentary of carbonate is analyzed using isotopes of carbon, oxygen, and strontium. The results indicate that porous carbonate reservoirs with porosities of 3%~5% mainly occur at the paleo-highland (Huanglong Formation and Chuanshan Formation) and the slope of paleo-highland (Hezhou Formation). The porous carbonate reservoirs of the Qixia Formation are only locally developed. In addition, the study area was dominated by a warm and humid tropical climate from the Carboniferous to Early Permian, with four sea-level eustatic fluctuation indicated by the negative and positive δ13C excursions. When the sea level fell, the study area was exposed and denuded, and the supply of terrigenous detrital was dominated, which significantly influenced the carbonate deposit and diagenesis. This study highlights that sedimentation was a key factor in controlling the quality of Carboniferous-Early Permian carbonate reservoirs. The methods proposed in this study can be used in other carbonate-dominated strata worldwide.