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Major fluctuations in carbon-isotope composition (−2.8 to +5.4‰), as well as in oxygen-isotope composition (−10.2 to −2.1‰), are documented for Hauterivian–Albian shallow-water platform carbonate deposits in Pădurea Craiului (Apuseni Mountains, Romania). A composite carbon- and oxygen-isotope curve reveals the OAE1a and OAE1b as the main oceanic anoxic events (OAEs). Black shales or organic-rich levels, generally associated with such events, are poorly developed in Pădurea Craiului, testifying to slightly different responses to the carbon cycle perturbation between shallow- and deep-water environments. Palaeotemperatures of about 16–35 °C can be envisaged for the Late Hauterivian and Barremian in Pădurea Craiului, similar to those inferred from belemnite stable-isotope data from the Bersek Quarry (Gerecse Mountains, Hungary). For the Early Aptian interval, the δ13C variation pattern in Pădurea Craiului is similar to that documented in the Rochovica section from the Slovak Western Carpathians, developed in a deeper-water environment, although the interval of variation in Pădurea Craiului corresponds better to other shallow-water environment sections in the western Tethys.

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Gold mining pollution has long-lasting effects on the environment, particularly through acid mine drainage (AMD) and heavy metal contamination. Monitoring and assessing the impact of this pollution is crucial, as well as evaluating the effectiveness of remediation efforts. In our study, conducted in the gold mining area of Zlatna (GMAZ), western Romania, we utilised on-site measurements of water temperature, pH, electrical conductivity, and dissolved oxygen, along with the quantification of culturable aerobic bacteria and microfungi using ready-to-use media plates. We also examined the taxonomic richness of water invertebrates (TRWI) and the environmental features of the sites. Our study found significant negative impacts on the water biota in mining areas, with microbial abundance proving to be a reliable indicator of AMD pollution. While water invertebrates can also serve as indicators of mining effects, their abundance alone may not always accurately reflect pollution levels at every site. This multiple-factor analysis highlights the influences of water type, geological characteristics, air temperature, and precipitation on the structure of the aquatic biota. We observed a natural attenuation of mining pollution in the GMAZ in the last seven years. This study demonstrates that the quantification of microbiota, along with TRWI and basic physicochemical parameters, can offer a cost-effective alternative to expensive monitoring methods for assessing mining pollution.

ABSTRACT. Two sections have been measured within the Lower Cretaceous deposits from the northern part of Pădurea Craiului: Osoiu Hill section and Subpiatră section. Thin sections representing more than 180 samples allowed us to present some results on the biostratigraphy, facies succession and the role of microbial structures in the genesis of these limestones. The Osoiu Hill section is dominated by fenestral limestones formed in the intertidal or in the shallow subtidal zone. Their formation is dominantly related to microbial mats. Based on foraminiferal assemblages we attribute a Lower Barremian age to these limestones. The succession in the Subpiatra section is dominated by shallow facies with rudists, corals and Bacinella. These limestones contain Mesorbitolina texana a foraminifer which indicate Gargasian age. A more dense spectrum of microbial structures characterize this section: thrombolitic crusts, Bacinella-Lithocodium type structures, cryptic carbonate marine veneers and rivulariacean-like cyanobacteria. The microbial structures played an important role in the genesis of carbonate sediments and their lithification in the two sections.