TY - JOUR

T1 - Omission and pacing of events at the Norian–Rhaetian and Triassic–Jurassic transitions in Britain

AU - Hounslow, Mark W.

AU - Posen, Paulette E.

AU - Warrington, Geoffrey

AU - Page, Kevin N.

PY - 2025/8/18

Y1 - 2025/8/18

N2 - Magnetostratigraphy, palynology and ammonite biochronology of the Staithes S-20 core are used in an integrated evaluation of the late Norian to early Hettangian successions in Britain. The polarity patterns of the Blue Anchor and Westbury formations differ from their counterparts in SW England, indicating younger and older ages, respectively, for those units in NE England. Magnetostratigraphy indicates an underlying Sevatian age hiatus coeval with the D5 disconformity of the German Keuper. The miospore succession from S-20 is divisible into zones like those from the St Audrie’s Bay section in SW England. Using magnetic susceptibility datasets for the earliest Hettangian chronozones from S-20, Lavernock, St Audrie’s Bay and Lyme Regis, a new method is used to derive a TimeOpt-based astrochronology for the earliest Hettangian. This is anchored to radioisotopic dates from Peru correlated into British sections using carbon isotope excursions. A brief reverse magnetozone in the basal Cotham Member in the Staithes S-20 core and the astrochronological evaluation demonstrate that CAMP volcanics are coeval with the end-Triassic extinction in UK sections. An eco-plant model assessment of the miospores indicates greater proportions of eurythermic and europhyte floras, suggesting stronger seasonality in palaeoclimate was probably a key factor in the end-Triassic extinction.

AB - Magnetostratigraphy, palynology and ammonite biochronology of the Staithes S-20 core are used in an integrated evaluation of the late Norian to early Hettangian successions in Britain. The polarity patterns of the Blue Anchor and Westbury formations differ from their counterparts in SW England, indicating younger and older ages, respectively, for those units in NE England. Magnetostratigraphy indicates an underlying Sevatian age hiatus coeval with the D5 disconformity of the German Keuper. The miospore succession from S-20 is divisible into zones like those from the St Audrie’s Bay section in SW England. Using magnetic susceptibility datasets for the earliest Hettangian chronozones from S-20, Lavernock, St Audrie’s Bay and Lyme Regis, a new method is used to derive a TimeOpt-based astrochronology for the earliest Hettangian. This is anchored to radioisotopic dates from Peru correlated into British sections using carbon isotope excursions. A brief reverse magnetozone in the basal Cotham Member in the Staithes S-20 core and the astrochronological evaluation demonstrate that CAMP volcanics are coeval with the end-Triassic extinction in UK sections. An eco-plant model assessment of the miospores indicates greater proportions of eurythermic and europhyte floras, suggesting stronger seasonality in palaeoclimate was probably a key factor in the end-Triassic extinction.

KW - palynology

KW - magnetostratigraphy

KW - cyclostratigraphy

KW - astrochronology

KW - ammonite biochronology

KW - Triassic–Jurassic boundary

U2 - 10.1017/s0016756825100162

DO - 10.1017/s0016756825100162

M3 - Journal article

VL - 162

JO - Geological Magazine

JF - Geological Magazine

SN - 0016-7568

M1 - e27

ER -