T169 Chemostratigraphy: Physical and Temporal Applications

Tuesday, 24 September 2019
8:00 AM - 12:00 PM
Room 224B, North Building

FORMAL BARREMIAN–ALBIAN CHEMOSTRATIGRAPHIC UNITS DEFINED BY ROCK PROPERTIES AND STANDARD SECTIONS

Paper number: T169-10
Program: Technical Sessions
Time: 10:20 AM – 10:35 AM

Authors

Abstract

Chemostratigraphy uses geochemical data to subdivide and correlate sedimentary stratigraphic successions. Chemostratigraphic Units (CUs) are a new category comparable to lithostratigraphic and biostratigraphic units but not yet formally defined in stratigraphic guides. Geochemical signals of organic matter, major, minor, and trace elements, and isotopes have been recognized as widespread, even synchronous intervals in stratigraphic sections since the 1970’s at least. For example, Cretaceous organic carbon-rich black shales define oceanic anoxic events (OAEs) and are correlated in deep sea and outcrop sections.

Six chemostratigraphic attributes and procedures define CUs objectively: 1) geochemical elements that produce reliable stratigraphic signals such as TOC, δ13C, δ18O, δ13C/ δ18O; 2) chemical signals with distinct identifiable quantifiable excursions; 3) closely spaced samples (e.g, 50 cm or less); 4) events defined at bases of excursions, at inflections, at peaks, or as interval between excursions; 5) events integrated with independent criteria, e.g., bioevents, magnetozones, or well log properties; and 6) events correlate from reference sections to other sections.

Barremian–Aptian carbon isotope zones were defined in Italy and Switzerland at Cismon and Rotter Sattel. Subsequently Aptian–Albian carbon isotope zones were identified in Mexico at Cañon Santa Rosa. Each section has well-documented microfossil biozones and magnetozones that enable the chemostratigraphic units to be integrated with a comprehensive Cretaceous time scale. These carbon-isotope zones are synchronous correlation units because they represent oceanographic and depositional events, and hence, incur time significance.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-335165

© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.