Exceptionally preserved calcified sponge assemblagesin Upper Jurassic carbonates of the eastern Getic Carbonate Platform (Southern Carpathians, Romania)

Abstract

A rich poriferan assemblage was identified within the easternmost part of the Getic Carbonate Platform of Romania (Grădiștei Gorges). The excellent preservation state of most poriferans here led to the discovery of a new species (Neuropora gigantea Pleș & Schlagintweit, n. sp.) and to the identification of previously unknown diagnostic features in some species (Sarsteinia babai Schlagintweit & Gawlick, 2006 emend., Neuropora lusitanica Termier, 1985, Sphaeractinia steinmanni Canavari, 1893). Calciagglutispongia yabei Reitner, 1992, Sarsteinia babai and Sphaeractinia steinmanni are reported for the first time from the Upper Jurassic carbonates of the Getic Carbonate Platform. The sedimentary input fluctuations and the nutrient competition had an important role in understanding the morphological adaptations of the analysed species. The existing palaeoecological and palaeoenvironmental conditions generated different distribution patterns towards the reef profile and also preferential adaptations to a specific Tethyan domain. As opposed to the poriferan assemblages from the northern Tethyan shelves, these organisms formed sponge-coral-microencruster boundstones at the margins and fore-reefal zones of isolated carbonate platforms within the intra-Tethyan realm. The importance of calcified sponges in reef-zonation is highlighted by the establishment of a general zonation model. Three zones can be distinguished: 1) Cladocoropsis-Milleporidium zone (back-reef area); 2) Bauneia-Chaetetopsis-Parastromatopora zone (central reef area); and 3) Sphaeractinia/Ellipsactinia-Neuropora zone for the fore-reef area. In the absence of a true reef framework these calcified sponges developed typical morphologies, environmental adaptations and partnerships with other biotic groups which strongly influenced the carbonate production throughout the intra-Tethyan domain.

A lost carbonate platform deciphered from clasts embedded in flysch: Štramberk-type limestones, Polish Outer Carpathians

“…Previously, such reefs were not distinguished among the Late Jurassic reefs (Leinfelder, 1993;Insalaco et al, 1997). This reef type is characteristic of, although possibly not limited to the isolated platforms of the Neo-Tethys (Schlagintweit and Gawlick, 2008;Pleş et al, 2021;Kołodziej and Ivanova, 2021). To recognize the microencruster-microbial-cement boundstones, it is necessary to study them in more than in a single thin-section.…”

“…Bacinellid and "Lithocodium"-like structures (commonly termed the "Lithocodium-Bacinella" association), Lithocodium aggregatum, Koskinobullina socialis, Iberopora bodeuri and Thaumatoporella parvovesiculifera are light-dependent taxa/biogenic structures, implying shallow-water reef, back-reef or lagoonal settings. Other species, listed in Table 1, have much broader environmental demands, but especially if photophilic microencrusters are absent, they imply fore-reef and slope settings (Leinfelder et al, 1993;Gawlick, 2008, 2011;Pleş et al, 2013Pleş et al, , 2021Kaya and Altıner, 2015;Kołodziej and Ivanova, 2021).…”

“…This type of boundstone is represented in the samples studied but is subordinate to FT 1. Microencruster-microbial-cement boundstones are unique to the intra-Tethyan carbonate platforms (Schlagintweit and Gawlick, 2008;Ivanova et al, 2008;Pleş et al, 2013Pleş et al, , 2016Pleş et al, , 2019Pleş et al, , 2021Hoffmann et al, 2017;Krajewski and Schlagintweit, 2018;Kołodziej and Ivanova, 2021). Schlagintweit and Gawlick (2008) were the first to notice in the Kimmeridgian and Berriasian of the Northern Calcareous Alps (Plassen Carbonate Platform) the crucial role of non-photophilic microencrusters and synsedimentary cements for the reef framework.…”