Jurassic-Cretaceous boundary bioevents and magnetochrons: A stratigraphic experiment

Scott, Robert W. ✉

Angol nyelvű Tudományos Szakcikk (Folyóiratcikk)
Megjelent: CRETACEOUS RESEARCH 0195-6671 1095-998X 100 pp. 97-104 2019
  • SJR Scopus - Paleontology: Q1
    The search for an Upper Jurassic-Lower Cretaceous Global Boundary Stratotype Section and Point has been elusive. Few evolutionary events are dramatic at this transition and paleoenvironmental and tectonic changes are subtle and local. Ammonites, calpionelids, calcareous nannofossils, and paleomagnetic reversals are the principle events that distinguish Tithonian-Berriasian-Valanginian stages.This quantitative stratigraphic experiment integrates the first and last occurrences of bioevents (FOs/LOs) with magnetochrons from biostratigraphic checklists of measured sections and cores. Events in forty-one well documented outcrops and deep-sea cores were cross-plotted in X/Y diagrams with a geologic time scaleto create hypotheses of synchroneity between section pairs. The correlation line of synchroneity extended the FOs and LOs in each section relative to other sections. The composited range extensions in all sections approximate first- and last-appearance datums (FADs, LADs) and comprise a database (LOK2016CS) calibrated to numerical ages (Ma). Two sections have reported radioisotope ages that constrain the ages of taxa. This stratigraphic experiment places the calpionellid, nannofossil and ammonite FADs in the predicted order relative to magnetochrons.The base of the Berriasian Stage is approximated by the FAD of Calpionella alpina, which is in uppermost M20n. Asssociated key nannofossil FADs are Nannoconus globulus globulus, Crucielllipsis cuvillieri, and Zeugrhabdotus erectus. The LAD of Crassicollaria intermedia is also close to these events. Base of the middle Berriasian Substage is the FAD of Subthurmannia subalpina at the base of the Subthurmannia occitanica Zone close to the base of Chron M18. Base of the upper Berriasian Substage is the FAD of Malbosiceras [Mazenoticeras] paramimounum at the base of the Subthurmannia boiseri Zone at about the boundary between chrons M17 and M16. The base of the Valanginian Stage is at the FAD of Thurmanniceras pertransiens and Calpionellites darderi and above the FAD of Calcicalathina oblongata, which correlates with the Chrons M15/M14. The base of the upper Valanginian is at the base of the Saynoceras verrucosum Zone in Chron M10n. (C) 2019 Elsevier Ltd. All rights reserved.
    Hivatkozás stílusok: IEEEACMAPAChicagoHarvardCSLMásolásNyomtatás
    2020-07-06 23:23