Age constraints on the dispersal of dinosaurs in the late triassic from magnetochronology of the los colorados formation (Argentina)

Dennis V. Kent, Paula Santi Malnis, Carina E. Colombi, Oscar A. Alcober, Ricardo N. Martínez

Research output: Contribution to journalArticlepeer-review

65 Scopus citations

Abstract

A measured magnetozone sequence defined by 24 sampling sites with normal polarity and 28 sites with reverse polarity characteristic magnetizations was established for the heretofore poorly age-constrained Los Colorados Formation and its dinosaur-bearing vertebrate fauna in the Ischigualasto-Villa Union continental rift basin of Argentina. The polarity pattern in this ∼600-m-thick red-bed section can be correlated to Chrons E7r to E15n of the Newark astrochronological polarity time scale. This represents a time interval from 227 to 213 Ma, indicating that the Los Colorados Formation is predominantly Norian in age, ending more than 11 My before the onset of the Jurassic. The magnetochronology confirms that the underlying Ischigualasto Formation and its vertebrate assemblages including some of the earliest known dinosaurs are of Carnian age. The oldest dated occurrences of vertebrate assemblages with dinosaurs in North America (Chinle Formation) are younger (Norian), and thus the rise of dinosaurs was diachronous across the Americas. Paleogeography of the Ischigualasto and Los Colorados Formations indicates prolonged residence in the austral temperate humid belt where a provincial vertebrate fauna with early dinosaurs may have incubated. Faunal dispersal across the Pangean supercontinent in the development of more cosmopolitan vertebrate assemblages later in the Norian may have been in response to reduced contrasts between climate zones and lowered barriers resulting from decreasing atmospheric pCO2 levels.

Original languageEnglish (US)
Pages (from-to)7958-7963
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume111
Issue number22
DOIs
StatePublished - Jun 3 2014

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Adamanian
  • La esquina
  • Magnetostratigraphy
  • Paleolatitude

Fingerprint Dive into the research topics of 'Age constraints on the dispersal of dinosaurs in the late triassic from magnetochronology of the los colorados formation (Argentina)'. Together they form a unique fingerprint.

Cite this