Mathematics – Logic
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27r.230h&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 230
Mathematics
Logic
3
Scientific paper
The uppermost Cretaceous chalk series is well exposed in Central Poland and its magnetostratigraphy has been established (Hansen et al. 1990). In the field 2.5-cm-diameter plugs were drilled spaced at 5-cm intervals (i.e., 20 plugs per meter corresponding to almost 50% coverage). All plugs were measured for their magnetic susceptibility and plotted against stratigraphic depth. The resultant curve from the Cretaceous part of magnetochron 29R corresponds to a time interval around 400 ky (Berggren et al. 1985). Magnetochron 29R has ben assigned a duration of 570-800 ky and contains the K/T boundary, where 2/3 of the time interval is earlier than the K/T boundary. In Fig. 1A two different periodicities are present. The larger peaks correspond to roughly 100 ky while the smaller corresponds to ca. 20 ky. No other frequencies are found. We suggest that the pulses correspond to the ellipse-precession complex in the Milankovitch band (compare Fisher and Bottjer 1991). Eight samples were analyzed by instrumental neutron activation. Four samples were from a pulse maximum and four from the neighboring trough. The results show a trace element doubling in the peak relative to the trough. By contrast the CaCO3 showed a decrease of 7% in the peak along with an increase in Sr of 4.2%. The drop in CaCO3 is much too low to account for the differences in trace elements. We suggest that the change is caused by variations in the early supply of terrigenuous material, mainly clay, related to variations in precipitation. We made a parallel study of the uppermost Maastrichtian red paleosoils with dinosaur nests from the region of Aix-en- Provence, South France. It disclosed the same pattern in susceptibility signal as that found in Poland (Fig. 1B). Here the magnetostratigraphy is also known (Hansen et al. 1989). We are thus dealing with a pattern common to both shallow water marine chalk and paleosoils. The interference pattern between the 100- and 20-ky cycles are in agreement in the two areas. This suggests to us that we are dealing with identical phenomena, where precipitation may affect both types of environments. Our method of study allows correlation (with a resolution of better than 10 ky) between marine and terrestrial deposits, timing of extinctions, estimates of accumulation rates plus realistic time estimates of magnetochrons. A study of the Uppermost Cretaceous chalk at the locality Nye Klov in North Jylland allows us to fix the extinction pattern of marine benthic fossils in a time frame. Detailed analysis of the boundary bed at Stevns Klint Karlstrup Quarry and Caravaca, Spain point at presence of two sediment pulses indicating a duration of Fish Clay time of around 40 ky. References: Berggren W. A., Kent D. V., and Flynn J. J. (1985) In The chronology of the geological record (ed. N. J. Snelling) Geol. Soc. Amer. Mem. 10, 141-195. Fisher A. G. and Bottjer D. J. (1991) Orbital forcing and sedimentary sequences. J. Sed. Petr. 61, 1063-1069. Hansen H. J., Rasmussen K. L., and Gwordz R. (1989) Cahiers de la Reserve Geologique de Haute Provence 1, 83-90. Hansen H. J., Rasmussen K. L., Gwordz R., Hansen J. M., and Radwanski A. (190) Acta Geologica Polinica 39, 1-12.
Gwozdz Rajmond
Hansen H. J.
Rasmussen Lars K.
Walaszczyk K. I.
No associations
LandOfFree
Time Structure of a Mass Extinction: The Cretaceous- Tertiary Boundary does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Time Structure of a Mass Extinction: The Cretaceous- Tertiary Boundary, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Time Structure of a Mass Extinction: The Cretaceous- Tertiary Boundary will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1209708