Michalik J.,Slovak Academy of Sciences |
Lintnerova O.,Comenius University |
Rehakova D.,Comenius University |
Boorova D.,State Geological Institute of Dionys Stur |
Simo V.,Slovak Academy of Sciences
Cretaceous Research | Year: 2012
The base of Lower Cretaceous sequence in the Manín Unit is erosive but without signs of subaerial emersion. Submarine erosion was triggered by bottom denivelization during Late Berriasian extension of the area. Sedimentation of planktogenic hemipelagic limestones started during latest Berriasian/earliest Valanginian and continued until Aptian.The presence of late Valanginian anoxic oceanic event was not confirmed with certainty in the Butkov sections. A δ 13C event in the Campylotoxus Zone inside the Ladce Fm pale limestone sequence indicates the expected global perturbation of the carbon cycle. The absence of any black shale record documents local oxic conditions in marginal part of the basin. Sedimentation of dark limestones of the overlying Mráznica Formation was associated rather with climate instability, general slight cooling and with fine terrigeneous input from dryland into basin.Isotope C curves indicate decreasing trend of δ 13C values from +2.5‰ to +1.5‰ PDB. Relatively highest values (2.5 to 2.6‰) were reached during Oblongata- nannofossil- and/or the Calpionellites calpionellid zones. As neither black shales, nor the main phase of the warming event limited by the Campylotoxus - Verucosum ammonite zones were recorded, the C - isotope excursion is interpreted as an effect of local changes.Colonization of soft bottom by epibenthic organisms was gradual and long-lasting. Benthic islands of epifauna formed around hard objects on muddy bottom (ammonite shells, etc.). Trend of increasing calcification of benthic organisms resulted in carbonate platform progradation (connected with submarine sliding, redeposition and carbonate clastic accumulation on toe of the slope). The carbonate platform covered the area until Late Aptian. Carbonate platform growth was stopped and the platform collapsed during middle Albian. Hard rock surface bored by infaunal organisms has been buried under thick sequence of pelagic marls. © 2012 Elsevier Ltd.