1 Nature and timing of Late Mississippian to Mid Pennsylvanian glacio-eustatic 2 sea-level changes of the Pennine Basin, UK 3 4 Colin N. Waters1* and Daniel J. Condon2 5 1British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG 6 2NERC Isotope Geoscience Laboratory, British Geological Survey, Kingsley Dunham Centre, 7 Keyworth, Nottingham, NG12 5GG 8 * E-mail:
[email protected] 9 10 Abstract: The Pennine Basin of northern England contains a comparatively complete 11 Serpukhovian–Moscovian succession characterised by high-resolution ammonoid zonation and 12 cyclic paralic sedimentation. Two new ID-TIMS zircon ages from a bentonite deposited during 13 the Arnsbergian (mid-Serpukhovian) regional substage and tonstein of earliest Bolsovian (early 14 Moscovian) regional substage, have been determined. The weighted mean 206Pb/238U ages of 15 328.34 ± 0.55 and 314.37 ± 0.53 Ma (total uncertainty), respectively, require modification of the 16 timescale for the Western Europe regional chronostratigraphy. 17 The areal extent of acme ammonoid facies are used as a proxy for the magnitude of 47 discrete 18 flooding events. Incised valleys (major sequence boundaries) are used as a proxy for the 19 magnitude of sea-level falls. The frequency of these events, in the light of the new radiometric 20 dating, indicates: (1) temporal coincidence between major glaciations in Gondwana and phases 21 of increased frequency of sequence boundaries in the Pennine Basin; (2) high amplitude flooding 22 surfaces have an average frequency of c. 400 ka; (3) average cycle durations during the 23 Pendleian–early Arnsbergian and Chokierian–Bolsovian, of c.111 ka and c.150 ka, respectively, 24 reflect short-duration eccentricities, and (4) multiple flooding surfaces with the same ammonoid 25 assemblages may equate with sub-100 ka precession/obliquity frequencies.