TY - JOUR

T1 - Palaeoclimate and palaeoenvironmental changes through the onset of the Valanginian carbon-isotope excursion

T2 - Evidence from the Polish Basin

AU - Morales, C.

AU - Kujau, A.

AU - Heimhofer, U.

AU - Mutterlose, J.

AU - Spangenberg, J. E.

AU - Adatte, T.

AU - Ploch, I.

AU - Föllmi, K. B.

N1 - Funding information: The authors would like to thank Tiffany Monier, and Jean-Claude Lavanchy for their assistance in laboratory work (RockEval and XRD preparation, and XRF measurements respectively), as well as André Villars for his slides preparation. We are also grateful to Prof. H. Weissert (ETH Zürich) and Prof. J.-F. Deconinck (University of Dijon) for their stimulating discussions. Prof. Nicolas Tribovillard (University of Lille) and two anonymous reviews helped to substantially improve an earlier version of this manuscript. Financial support from the Swiss National Science Foundation (project 200020_126455 ) and the Polish Ministry of Science and Higher Education (project 61.3601.0901.00.0 ) are appreciatively acknowledged.

PY - 2015/5/5

Y1 - 2015/5/5

N2 - The Valanginian Weissert episode of environmental change is associated with a positive carbon-isotope excursion (CIE) in δ13Ccarb and δ13Corg records and a crisis in pelagic and neritic carbonate production. The CIE was interpreted to represent the first oceanic anoxic event (OAE) of the Cretaceous, linked with the formation of the Paraña-Etendeka large igneous province (LIP). Recent studies suggest though that the extent of oceanic anoxia was limited to high-latitude epicontinental seas and the Pacific, and that the Paraña-Etendeka LIP postdates the Valanginian CIE. With these new interpretations, the palaeoenvironmental changes behind the observed perturbation of the carbon cycle remain to be elucidated. Here we present sedimentological and geochemical results from a drill core near Wąwał, central Poland. The excavated succession is of particular interest due to its near-shore depositional setting within the former Polish Basin and its preservation (up to 17wt.% of aragonite). The core consists of lower to upper Valanginian silty to sandy clays deposited under fully marine conditions on top of an Upper Jurassic karstified limestone. A change in weathering mode from very humid and highly hydrolysing towards less humid and seasonally contrasted conditions is indicated by the abrupt change from a kaolinite- to a smectite-dominated clay-mineral association near the boundary between the early and late Valanginian. Moreover, two phosphate-rich horizons were identified, which correlate in time to northern Tethyan occurrences in the Helvetic Alps. The lower level is associated with the early Valanginian transgression and corresponds to peak humidity recorded in the Wąwał core. The upper layer corresponds to the paroxysmal phase of the Valanginian crisis in carbonate production. In the Wąwał core, evidence for anoxic conditions during the Valanginian CIE is lacking. The climatic conditions and changes identified in the Polish Basin are different from those of the northern Tethyan area, where an increase in humidity is observed near the early-late Valanginian boundary. The contrasting climate conditions are probably an expression of latitudinal shifts in the position of the northern mid-latitude humid belt.

AB - The Valanginian Weissert episode of environmental change is associated with a positive carbon-isotope excursion (CIE) in δ13Ccarb and δ13Corg records and a crisis in pelagic and neritic carbonate production. The CIE was interpreted to represent the first oceanic anoxic event (OAE) of the Cretaceous, linked with the formation of the Paraña-Etendeka large igneous province (LIP). Recent studies suggest though that the extent of oceanic anoxia was limited to high-latitude epicontinental seas and the Pacific, and that the Paraña-Etendeka LIP postdates the Valanginian CIE. With these new interpretations, the palaeoenvironmental changes behind the observed perturbation of the carbon cycle remain to be elucidated. Here we present sedimentological and geochemical results from a drill core near Wąwał, central Poland. The excavated succession is of particular interest due to its near-shore depositional setting within the former Polish Basin and its preservation (up to 17wt.% of aragonite). The core consists of lower to upper Valanginian silty to sandy clays deposited under fully marine conditions on top of an Upper Jurassic karstified limestone. A change in weathering mode from very humid and highly hydrolysing towards less humid and seasonally contrasted conditions is indicated by the abrupt change from a kaolinite- to a smectite-dominated clay-mineral association near the boundary between the early and late Valanginian. Moreover, two phosphate-rich horizons were identified, which correlate in time to northern Tethyan occurrences in the Helvetic Alps. The lower level is associated with the early Valanginian transgression and corresponds to peak humidity recorded in the Wąwał core. The upper layer corresponds to the paroxysmal phase of the Valanginian crisis in carbonate production. In the Wąwał core, evidence for anoxic conditions during the Valanginian CIE is lacking. The climatic conditions and changes identified in the Polish Basin are different from those of the northern Tethyan area, where an increase in humidity is observed near the early-late Valanginian boundary. The contrasting climate conditions are probably an expression of latitudinal shifts in the position of the northern mid-latitude humid belt.

KW - Carbonate crisis

KW - Climate change

KW - Polish Basin

KW - Valanginian

KW - Weissert episode

UR - http://www.scopus.com/inward/record.url?scp=84925387281&partnerID=8YFLogxK

U2 - 10.1016/j.palaeo.2015.03.013

DO - 10.1016/j.palaeo.2015.03.013

M3 - Article

AN - SCOPUS:84925387281

VL - 426

SP - 183

EP - 198

JO - Palaeogeography, Palaeoclimatology, Palaeoecology

JF - Palaeogeography, Palaeoclimatology, Palaeoecology

SN - 0031-0182

ER -