Upper Aptian calcareous algae from Pădurea Craiului ( Northern Apuseni Mountains , Romania )

A study of calcareous strata previously assigned to the Barremian-Early Aptian interval in the northwestern part of Pădurea Craiului, (Apuseni Mountains), led to the identifi cation of a micropaleontological association indicative of a Late Aptian age. Unequivocal evidence for the Late Aptian assignment of these limestones is the presence throughout the sequence of two orbitolinid species, Mesorbitolina texana (ROEMER) and Mesorbitolina subconcava (LEYMERIE). The most interesting sections are located in the neighbourhood of Subpiatră, where both outcrops and a quarry facilitated detailed analyses. In this area, the Upper Aptian succession consists basically of three types of macrofacies: 1) limestone with rudists; 2) limestone with Bacinella and 3) limestone with corals, each of them showing several types of microfacies. Bacinella structures are the most common feature in the whole succession, irrespective of the macrofacies. This paper focuses on an algal association that was identifi ed in several levels within the succession. Dasycladalean algae are more frequent, and are commonly found in grain-dominated fabrics (mostly grainstone textures), in association with orbitolinid foraminifera and bioclasts of corals, rudists and gastropods. However, a few species are present only in mud-dominated fabrics (i.e. lower-energy intervals). The dasycladalean association from the Upper Aptian deposits of Pădurea Craiului is of special interest, for this group registered a dramatic decline at the Lower Aptian/Upper Aptian boundary, as confi rmed by the relative scarcity of the Dasycladales in the Upper Aptian carbonate deposits.


INTRODUCTION, STRATIGRAPHIC FRAMEWORK
The Pădurea Craiului Massif includes Mesozoic deposits of Triassic, Jurassic and Cretaceous age.Samples were collected from several profi les in the Subpiatră quarry (near the Aleşd locality, in the northwestern part of the Pădurea Craiului Mountains (Fig. 1) and were assigned into the local Cretaceous succession.The lowermost Cretaceous strata lie unconformably on a surface deformed by regional uplift at the end of the Upper Jurassic.The sequence begins with bauxites that are overlain by carbonate deposits assigned to discrete lithostratigraph ic units, from bottom to top as follows (Fig. 2): 1) Blid Formation (DRAGASTAN et al., 1986(DRAGASTAN et al., , 1988)).This formation includes two members (COCIUBA, 2000): 1. a) The Dobreşti Member overlies bauxites or rests directly on Upper Jurassic limestone.Originally, the basal limestone of the Dobreşti Member contains lacustrine deposits, which are followed by brackish and fi nally by normal marine strata; in the literature they are known as »Limestone with characeans and gastropods« (PATRULIUS in IANOVICI et al., 1976).Besides characeans and gastropods, this limestone con tains dasycladalean algae and foraminifera, an assemblage with a low value regarding its stratigraphic resolution that however indicates a Berriasian-Hauterivian range.1. b) The Coposeni Member, previously known as the »Lower pachyodont limestone« (PATRULIUS in IANOVICI et al., 1976), is Upper Hauterivian-Barremian in age.
The foraminiferal association identifi ed in the lowermiddle part of this limestone contains Paracoskinolina?jourdanensis (FOURY & MOULLADE), an index foraminifer for the Upper Hauterivian p.p. and Lower Barremian.
3) The Valea Măgurii Limestone Formation (COCIUBA, 2000) rests on the Ecleja Marls and its upper limit is the site of an unconformity.This formation is also of Early Aptian age (most probably late Bedoulian).Both the Valea Bobdei Limestone and the Valea Măgurii Limestone include the orbitolinid Palorbitolina lenticularis (BLUMEN-BACH), a fossil that ranges from the Late Barremian to the Early Aptian.
4) The Vârciorog Formation (COCIUBA, 2000) is the new designation for the previously defi ned »Formation of the glauconitic sandstones and the upper pachyodont limestones« (PATRULIUS in IANOVICI et al., 1976).In the Varciorog area, the limestone interbeds are 15-20 m thick and contain Mesorbitolina texana.The Vârciorog Formation was assigned to the Upper Aptian (Gargasian) -Albian interval.The limestone of the Subpiatră quarry belongs to this same formation.A section in the southern part of the study area was the object of a preliminary investigation (DAOUD et al., 2004).

CARBONATE FACIES AND AGE OF THE VÂRCIOROG FORMATION LIMESTONE
Macroscopically, three major facies could be identifi ed: biostromes with rudists, limestone with Bacinella nodules and coral bioconstructions with their associated unique facies (Fig. 3).Their study under the microscope showed several types of microfacies all characterized by an abundance of Bacinella, (its occurrence is most conspicuous in a bindstone with Bacinella, and in a bioclastic wackestone-packstone with Bacinella oncoids), followed by somewhat lesser quantities in wackestone-packstone and coarse bioclastic grainstone, packstone and boundstone with rudists, coral boundstone and peloidal-

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Rivulariacean-type cyanobacteria. in thickness and show clear evidence of gravitational fl ow.In the Subpiatră quarry, the age equivalent limestone beds are120-150 m-thick and are typical carbonate platform deposits.Presumably, the carbonate succession in the Subpiatră quarry area represents the Upper Aptian carbonate platform that provided the gravitational fl ows found in the Vârciorog area where terrigenous deposits with a »fl ysch-like« character predominate.

THE CALCAREOUS ALGAE
An algal association was identifi ed at several levels in the succession.1993;BODROGI et al., 1994;BUCUR, 2000;SOTAK & MIŠIK, 1993) or it has been transferred to the genus Cylindroporella (C.ivanovici) (see MANCINELLI, 1992;MASSE & ISINTEK, 2000).SOKAČ ( 2004) has revised the genus Korkyrella by designating a lectotype for Salpingoporella texana JOHNSON, 1965 and has redefi ned the species Korkyrella texana (a taxonomic procedure that may cause a homonymy thus leading to another invalidation of the genus Korkyrella).
The relationship between Cylindroporella ivanovici and Cylindroporella barnesii JOHNSON (1954), has been discussed by BUCUR (2000), who shows that often the two species have been distinguished on the basis of »stratigraphic« criteria and may represent, in fact, a single species (see also CONRAD, 1982).
But to confi rm this, a careful review of the type species would be required.PRATURLON, 1964;Acicularia intermedia, DRAGASTAN, 1967;Terquemella concava, BERNIER, 1979).As a rule, the assignment of these objects to either one of the two organogenera was based on ambiguous or subjective criteria.Most of them have been assigned to the genus Acicularia.However, some have been reconsidered and assigned to the genus Terquemella (e.g.T. endoi and T. antiqua, see MASSE, 1995;MASSE & ARNAUD-VANNEAU, 1999).Here again a complete review is needed to clarify the taxonomy of the group.In our opinion, there is a simple and effi cient morphological criterion that may be used to differentiate the two genera: the presence of »club-shaped« longitudinal sections clearly links the gametophores' construction to the reproductive disk of Acicularia (e.g.Acicularia sp., KUSS & HERBIG, 1993).If the shape is spheroidal, ovoidal or discoid an affi liation with the genus Terquemella is much more probable.This distinction is obvious when a large number of specimens are found in one sample (fossil assemblage), as is the case of the Upper Aptian limestone samples from Pădurea Craiului: they show discoid morphologies.The specimens illustrated in Pl. 2, fi g. 8 represent, most probably, a new species.
Zittelina sp.(Pl. 3,Figs. 6,9) The genus Zittelina is represented in Lower Cretaceous deposits by only one species (Zittelina hispanica MASSE et al., 1993) that was identifi ed fi rst in the Hauterivian of Spain and then recorded in the Barremian-Aptian deposits of the Reşiţa Zone (Southern Carpathians, Romania, cf. BUCUR, 2001).However, the specimens identifi ed in the Upper Aptian of the Pădurea Craiului area differ from Zittelina hispanica in several morphological and dimensional parameters, so they may be a separate new species.Similar specimens have been illustrated by CAMOIN (1982, pl. 1, fi VANNEAU (1995) have also illustrated Zittelina sp. from Albian deposits on a »guyot« of the northwestern Pacifi c Ocean.These authors consider their specimen to be a new species.It is similar to the form we described from Pădurea Craiului.The study of this alga is in progress based on additional material recently collected from the Subpiatră quarry (Pădurea Craiului).
We have identifi ed several other dasycladalean algae from single specimens or from a limited numbers of specimens, so these sparsely represented forms have been assigned only at the generic level (?Clypeina sp., Dissocladella sp., Neomeris sp.-most probably a fragment of Neomeris cretacea, Russoella sp., Salpingoporella sp., Triploporella sp.-Pl.3, Fig. 8).
Coptocampylodon fontis (PATRULIUS, 1966) (Pl.2, Fig. 3pars) This incertae sedis microfossil is very common in the Barremian-Aptian deposits of the Tethyan domain.The clarifi cation of its taxonomy is beyond the scope of this paper.It would require a complex investigation that could clarify the status of the genus Coptocampylodon and the possible affi liation of the species C. fontis to this genus or to Carpathoporella DRA-GASTAN 1967.The most recent papers diverge in their points of view on this subject (e.g.MASSE & ARNAUD VANNE AU, 1999;RADOIČIĆ, 2005).Remarks on the taxonomy and detailed synonymy of Coptocampylodon are given in SCHLAG-INTWEIT et al. (2002).Beyond this aspect, it is notable that in the Pădurea Craiului area C. fontis is abundant in the Aptian-Albian allodapic limestones that are interbeds in the Vârciorog Formation.
The association identifi ed in the Upper Aptian limestones of Pădurea Craiului includes two red algae: Polystrata alba (PFENDER) and Parachaetetes asvapatii PIA.Polystrata alba (Pl.2, Fig. 4) is a peyssonneliacean alga occurring frequently in reef or para-reef deposits within the Hauterivian-Oligocene (?Miocene) time interval.Recent articles on this alga are by BASSI (1997) and AGUIRRE & BRAGA (1999).Parachaetetes asvapatii (Pl.2, Fig. 7) is usually assigned to the solenoporaceans, and as a rule it has been found in Upper Cretaceous -Palaeocene deposits, but it was identifi ed in Lower Cretaceous strata (GRANIER et al., 1991), and probably, also in the Upper Jurassic (BUCUR et al., 2005).Recent papers on Parachaetetes asvapatii were published by STOKAR (2000) and AGUIRRE & BARATTOLO (2001); the latter's article questioned the affi liation of this alga to the solenoporaceans.Elianella elegans PFENDER & BASSE 1948 has been considered by several authors as a recent synonym of Parachaetetes asvapatii (e.g.MOUSSAVIAN, 1989).Recently, BUČEK & KÖLER (2005), based on material from the Slovakian Palaeocene, reconsidered this synonymy, favouring the preservation of two separate species.
Finally, concerning the rivulariacean-type cyanobacteria (Pl.2, Figs.5-6) we can state only that they are present in some shallow subtidal or intertidal facies Concerning the palaeoenvironment of the Upper Aptian algae in the Pădurea Craiului area, the dasycladalean algae have been found mainly in coarse-grained facies that include fragments of corals, rudists and gastropods.Only Terquemella sp. is present in facies representing low energy environments.However, Polystrata alba and Parachaetetes asvapatii occur in reef facies, the fi rst as crusts associated with Bacinella, rudists or corals; the second is more common in environments dominated by corals.

CONCLUSION
The Upper Aptian carbonate deposits cropping out in the Subpiatră quarry area (Aleşd, Pădurea Craiului Mountains) most probably represent the carbonate platform from which the allodapic interbeds of the Vârciorog Formation were derived.We have identifi ed in these deposits an association of calcareous algae dominated by dasycladaleans, and accompanied by red algae and rivulariacean-type cyanobacteria.Among the dasycladaleans, two species (Terquemella sp. and Zittelina sp.) are most probably new.Given the dramatic decline in both numbers and species of the calcareous algae (dasycladales in particular) in the vicinity of the Lower Aptian/Upper Aptian boundary (BUCUR, 1999), the dasycladalean association from the Upper Aptian of Pădurea Craiului described here acquires a special palaeontological and palaeogeographical signifi cance.