Early Cretaceous fine grained carbonate resedimentation within pelagic deposits (Northern Calcareous Alps, Austria) – first results based on biostratigraphy and magnetic susceptibility

Thin bedded marly to cherty limestones with fine-grained resediment layers of Early Cretaceous age (Schrambach Formation, Northern Calcareous Alps, Leube quarry near Salzburg) were investigated to correlate magnetic... [ view full abstract ]

Thin bedded marly to cherty limestones with fine-grained resediment layers of Early Cretaceous age (Schrambach Formation, Northern Calcareous Alps, Leube quarry near Salzburg) were investigated to correlate magnetic susceptibility with high-resolution biostratigraphy.
The microfacies show radiolarian/calpionellid wacke-to packstones. The age is Valanginian (Tintinnopsella Zone) based on the occurrence of: Remaniella sp., Tintinnopsella carpathica (Murgenau&Filipescu), and cysts Cadosina semiradiata fusca Wanner, Cadosina semiradiata semiradiata Wanner , Stomiosphaera wanneri Borza, Colomisphaera carpathica (Borza), Colomisphaera vogleri (Borza), Carpistomiosphaera valanginiana BORZA, and Colomisphaera conferta Řehánek.
Some levels in the succession interestingly show A) a late Berriasian age (Simplex Subzone or Oblonga Subzone) based on the occurrence of: Calpionella alpine Lorenz, Calpionella elliptica Cadisch, Crassicollaria parvula Remane, Remaniella cadischiana (Colom), Remaniella duranddelgai Pop, Tintinnopsella carpathica (Murgenau&Filipescu), Lorenziella hungarica Knauer & Nagy, Calpionellopsis simplex (Colom), Calpionellopsis oblonga (Cadisch), Colomisphaera carpathica (BORZA), Colomisphaera lapidosa (Vogler), Cadosina semiradiata fusca Wanner, Cadosina semiradiata semiradiata Wanner. Or B) a middle Berriasian age (Elliptica Subzone) with Calpionella alpine Lorenz, Calpionella elliptica Cadisch, Crassicollaria parvula Remane, Tintinnopsella carpathica (Murgenau&Filipescu), Tintinnopsella doliphormis (Colom), Remaniella ferasini (Catalano), Remaniella colomi Pop, Remaniella duranddelgai Pop, Lorenziella hungarica , Knauer & Nagy and Lorenziella plicata Remane.
In these older horizons in the section the calpionelid loricas are poorly preserved, fine-grained debris of spicules, ostracods and crinoids appear. Some of them can be determined as Saccocoma, indicating a late Jurassic age.
A parallel section shows coarser-grained turbidite layers with reworked material from the Late Jurassic to earliest Cretaceous, but only in the coarser resediments. Here the resedimentation started in the Late Berriasian.
The detailed microfacies analysis and biostratigraphy documents clearly, that also in very fine-grained sedimentary rocks, which are normally interpreted as normal deep-water sedimentation very fine-grained redeposition of older material can be observed. The moderate preservation of the calpionellids and the age dating are the only hints for reworking processes, redeposition from shallower areas and a mixture with older material.
The study of magnetic susceptibility shows several horizons of increased supply of terrigenous material into the basin which coincides with microfacies and stratigraphic observations