Premium
A Milankovitch scale for Cenomanian time
Author(s) -
Gale Andrew S.
Publication year - 1989
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1989.tb00403.x
Subject(s) - milankovitch cycles , geology , cenomanian , cyclostratigraphy , authigenic , paleontology , ammonite , glauconite , precession , structural basin , cretaceous , glacial period , sedimentary rock , physics , astronomy
ABSTRACT A detailed cyclostratigraphy is present in the rhythmically bedded Cenomanian hemipelagic chalks of the northern Anglo‐Paris Basin, which can be correlated over 100,000 km 2 . Individual decimetre‐scale couplets probably represent the precession cycle (modes at 18 or 23 kyr), and can be readily grouped in sets averaging five, indicative of the short cycle of eccentricity (100 kyr). A composite cyclostratigraphy for the basin is presented here, and is used as the basis for a Cenomanian time‐scale (20 and 100 kyr units). The total duration of the Cenomanian thus obtained (4.4 Myr) compares well with recent radiometric dates of 4.0–4.5 Myr. The time‐scale is used to estimate the length of ammonite, inoceramid, and planktonic foraminiferal zones, the rates of formation of authigenic minerals (glauconite), sedimentation rates and the duration of transgressions and anoxic events.