Piatra Craiului Massif is located in the eastern part of South Carpathians, Romania. The sedimentary succession consists of Kimmeridgian-Berriasian-Lower Valanginian fore-ref, reef and peritidal carbonates. The fore-reef and... [ view full abstract ]
Piatra Craiului Massif is located in the eastern part of South Carpathians, Romania. The sedimentary succession consists of Kimmeridgian-Berriasian-Lower Valanginian fore-ref, reef and peritidal carbonates. The fore-reef and reef environments are characterised by the presence of coral-microbial boundstones and coarse, poorly sorted rudstones. Micropaleontological assemblage consists of encrusting organisms (Crescentiella morronensis, Lithocodium aggregatum, Bacinella irregularis, Koskinobulina socialis, Radiomura cautica, Perturbatacrusta leini). Corals are commonly encrusted by Bacinella-Lithocodium crusts. The internal sediment is a peloidal wackestone with Neuropora lusitanica and Perturbatacrusta leini. Crescentiella morronensis is the most common encrusting organism.
These deposits are overlain by 20 m thick high energy subtidal deposits which are characteristic for carbonate platform margins. The facies comprise coarse bioclastic intraclastic grainstone with black pebbles, ooidic grainstone and oncoidic bioclastic grainstone. Microfossils are represented by dasycladalean algae (Salpingoporella pygmaea, Salpingoporella annulata, Steinmaniporella kapelensis, Clypeina sulcata, Campbelliella striata, Neoteutloporella socialis) and foraminifera (Parurgonina caelinensis, Neokilianina rahonensis, Mohlerina basiliensis).
Other bioclasts include bivalves, gastropods, sponges and coral fragments. They are broken and regenerated ooids may be present. Gastropods and dasycladalean algae are coated by a milimeter thick micritc rim. This sedimentary feature indicates that these bioclasts were micritised in restricted lagoons being subsequently reworked in these high energy environments.
The uppermost part of the succession consists of 300 m thick interbeddings of low energy subtidal limestones and intertidal-supratidal carbonate rocks. The low energy subtidal limestones are defined by bioclastic wackestones with dasycladalean algae (Salpingoporella annulata, Salpingoporella praturlonii, Pseudocymopolia jurassica, Clypeina sulcata, Clypeina parasolkani), thick shell bivalves, gastropods and cyanobacteria nodules. The presence of thick shell bivalves and cyanobacteria nodules indicates deposition in protected, restriced lagoons. Some dasycladalean algae such as Clypeina sulcata or Salpingoporella annulata occur as monospecific, whole fossils in a wackestone type facies and they can be interpreted as being in situ.
The intertidal-supratidal limestones contain mainly rivularian type cyanobacteria and rare foraminifera (Pfenderina neocomiensis, Conicopfenderina ? balkanica, Pseudotextulariella courtionensis, Coscinoconus alpinus, Coscinoconus cherchiae, Pseudocyclammina lituus, Vercorsella camposauri, Haplophragmoides joukowskyi).
In conclusion, the entire carbonate succession is a prograding, shallowing upward megasequence. In the basal part, the development of large scale bioconstructions was influenced by the presence of abundant encrusting organisms and calcimicrobes. The presence of cyanobacteria rich, intertidal-supratidal carbonates indicates that as the carbonate platform was prograding the accommodation space was reduced and sediments were produced mainly by cyanobacteria.
This study is a contribution to the CNCS research project financed by the PN-II-ID-PCE-2011-3- 002 grant.
