Magnetostratigraphy, biostratigraphy, and chemostratigraphy of the Pignola-Abriola section: New constraints for the Norian-Rhaetian boundary

Abstract

A detailed magnetostratigraphic investiga-\ud tion of the Pignola-Abriola section of Norian\ud to Rhaetian age permits the identification of\ud 22 magnetic polarity reversals grouped in 10\ud magnetozones. We correlate the magneto-\ud stratigraphy of the Pignola-Abriola section\ud with the Newark astrochronological polarity\ud time scale (APTS). In total, 19 correlation\ud options were tested, and only one (option 7)\ud yielded a statistically significant correlation\ud that was consistent with the available infor-\ud mation on the stratigraphic age of the Newark\ud APTS. After some adjustments to minimize\ud erratic variations in sediment accumulation\ud rates, a final correlation (option 7.1) was used\ud to generate an age model of sedimentation\ud for the Pignola-Abriola section. The Pignola-\ud Abriola section has been correlated with\ud Rhaetian sections from the literature, notably\ud the current global boundary stratotype sec-\ud tion and point candidate for the base of the\ud Rhaetian at Steinbergkogel, Austria, where\ud the Norian-Rhaetian boundary is proposed\ud to be placed at a stratigraphic level contain-\ud ing the first appearance datum (FAD) of\ud conodont Misikella posthernsteini, traced on\ud the Newark APTS to ca. 209–210 Ma. Issues\ud regarding the taxonomy of M. posthernsteini,\ud a species characterized by transitional forms\ud with its ancestor Misikella hernsteini, lead us\ud to propose the alternative option of placing the\ud Norian-Rhaetian boundary at a prominent\ud negative δ13C spike observed in the Pignola- org\ud Abriola section at meter 44.5, 50 cm below the level containing the FAD of M. posthernsteini sensu stricto and close to the base of radiolarian Proparvicingula moniliformis zone. This level has been magnetostratigraphically cor- related to Newark magnetozone E20r.2r at ca. 205.7 Ma. Assuming an age of ca. 201.3 Ma for the Triassic-Jurassic boundary, the Rhaetian Stage would have a duration of ~4.4 m.y

The Rhaetian (Late Triassic) vertebrates of Hampstead Farm Quarry, Gloucestershire, UK

“…The temporal duration of the Westbury Formation was estimated by Macquaker (1994) as 1.66-5 Myr, although we will consider a maximum of 2 Myr (assuming the Westbury Formation is half the Rhaetian, matched in duration by the overlying Lilstock Formation; total duration of Rhaetian, 4.4 Mr: Maron et al, 2015), and so many cycles of sedimentation are likely included, and much time is unrepresented by sediment. (Macquaker, 1994;Suan et al, 2012).…”

“…The Rhaetian as a stratigraphic stage has also had a chequered history, and its duration is currently debated, with estimates ranging from 7-8 Myr (Muttoni et al, 2010) to 4.4 Myr (Maron et al, 2015). In central Europe and the United Kingdom, the beginning of the Rhaetian is marked by the Rhaetian Transgression, dated at 205.7 Ma (Maron et al, 2015), when marine waters and sediments flooded over the underlying Mercia Mudstone Group.…”

“…In central Europe and the United Kingdom, the beginning of the Rhaetian is marked by the Rhaetian Transgression, dated at 205.7 Ma (Maron et al, 2015), when marine waters and sediments flooded over the underlying Mercia Mudstone Group. In Britain, the Mercia Mudstone Group red beds pass up into the Blue Anchor Formation, and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 5…”

The first discovery of crinoids and cephalopod hooklets in the British Triassic

“…The Rhaetian is the short (205.7-201.3 Ma;Maron et al, 2015) final stage of the Triassic. It was a time of significant environmental change marked by a marine regressiontransgression couplet that extended over much of Europe, including Britain (Hallam, 1997), and culminating in the end-Triassic mass extinction.…”

The Rhaetian vertebrates of Chipping Sodbury, South Gloucestershire, UK, a comparative study

“…During this short span of time (205.7-201.3 Myr ago; Maron et al, 2015), Pangaea began to break up (de Lamotte et al, 2015), and this presumably greatly influenced the global climate system by driving cyclical extremes of climate (Trotter et al, 2015). The Rhaetian was terminated by the end-Triassic mass extinction, which saw the rapid, global extinction of ~50% of marine and terrestrial genera (Deenen et al, 2010), including the conodonts and many marine reptiles and invertebrates, as well as many archosaurs, some therapsids, and most temnospondyl amphibians.…”