Astrochronostratigraphic polarity time scale (APTS) for the Late Triassic and Early Jurassic from continental sediments and correlation with standard marine stages

Article history: Received 22 July 2016 Received in revised form 23 December 2016 Accepted 23 December 2016 Available online 05 January 2017 Paleomagnetic and cycle stratigraphic analyses of nearly 7000m of section from continuous cores in the Newark basin and an overlapping 2500meter-thick composite outcrop and core section in the nearby Hartford basin provide an astrochronostratigraphic polarity time-scale (APTS) for practically the entire Late Triassic (Carnian, Norian and Rhaetian) and the Hettangian and early Sinemurian stages of the Early Jurassic (233 to 199 Ma in toto). Aperiodic magnetic polarity reversals make a distinctive pattern of normal and reverse chrons for correlation, ideally paced by the periodic timing of orbital climate cycles, and anchored to million years ago (Ma) by high-precision U-Pb zircon dates from stratigraphically-constrained basalts of the Central Atlantic Magmatic Province (CAMP). Pinned by the CAMPdates, the Newark-Hartford APTS is calibrated by sixty-sixMcLaughlin cycles, each a reflection of climate forcing by the long astronomical eccentricity variation with the stable 405 kyr period, from 199.5 to 225.8Ma and encompassing fifty-onemagnetic polarity intervals, making it one of the longest continuous astrochronostratigraphic polarity time-scales available in theMesozoic and Cenozoic. Extrapolation of sediment accumulation rates in fluvial sediments in the basal Newark section extends the sequence an additional fifteen polarity intervals to 232.7 Ma. The lengths of the 66 polarity chrons vary from 0.011 Myr (Chron E23r) to 1.63Myr (ChronH24n)with an overall mean duration of 0.53Myr. The oldest CAMP basalts provide a zircon U-Pb-based estimated age of 201.5 Ma for the base of the stratigraphically superjacent McLaughlin cycle 61 and 201.6 Ma using cycle stratigraphy for the onset of the immediately subjacent Chron E23r. The calibration age of 201.5Ma for the base of McLaughlin cycle 61 is remarkably consistent with the calculated phase of the 498th long eccentricity cycle counting back using a period of 405 kyr from themost recent peak at 0.216Ma. Accordingly, we suggest a nomenclature (Ecc405:k, where k is the cycle number or fraction thereof) to unambiguously assign ages from the astrochronostratigraphy. Magnetostratigraphic correlation of key Tethyan sections with diagnostic marine biostratigraphic elements to the Newark-Hartford APTS allows determination of numerical ages of standardmarine stages, as follows: 227Ma for the Carnian/Norian boundary, 205.5Ma for theNorian/ Rhaetian boundary (using a chemostratigraphic criterion, or about 4 Myr older for alternative criteria), 201.4Ma for the Triassic/Jurassic boundary, and 199.5 Ma for the Hettangian/Sinemurian boundary. These age estimates are in excellent agreement with available constraints from high-precision U-Pb zircon dating from the Pucara Basin of Peru and along with the presence of the short Chron E23r in several basins argue strongly against suggestions that millions of years of Rhaetian time ismissing in a cryptic hiatus or unconformity that supposedly occurs just above Chron E23r in the Newark Supergroup basins. It is more parsimonious to explain the apparent temporal delays in appearances and disappearances of palynoflora, conchostracans, and other endemic taxa in continental deposits as a reflection of demonstrated continental drift across climate belts and the misinterpretation of ecostratigraphy as chronostratigraphy. The Newark-Hartford APTS provides a chronostratigraphic template for continuing efforts at correlation of Late Triassic and Early Jurassic continental and marine sections throughout the world, including integration with atmospheric pCO2 measurements from paleosol carbonates and carbon isotopic measurements from marine carbonates to better understand the global carbon cycle as well as understanding the causes of and recovery from the end-Triassic mass extinction. © 2017 Elsevier B.V. All rights reserved. Earth-Science Reviews 166 (2017) 153–180