Early Central Atlantic Ocean seafloor spreading history

Abstract

Twenty-three Mesozoic "Chrons" (specifi c time intervals) from M0 to M40, including several in the Jurassic Magnetic Quiet Zone ("Jurassic Quiet Zone"), as well as Cenozoic Chron C34, are identifi ed and mapped between the Atlantis and Fifteen-Twenty fracture zones on the North American plate, and between the Atlantis and Kane fracture zones on the African plate. Asymmetric seafl oor spreading is indicated by the distances spanned over Chron intervals for the western and eastern fl anks of the Central Atlantic ocean basin: C34 to the Mid-Atlantic Ridge (84 Ma to 0 Ma), M0 to C34 (120.6 Ma to 84 Ma), and M25 to M0 (154 Ma to 120.6 Ma). Chron M40 (167.5 Ma) is mapped ~65 km outboard of the S1 magnetic anomaly over the African fl ank, and its conjugate, the Blake Spur Magnetic Anomaly ("Blake Spur Anomaly") over the North American fl ank. Another pair of conjugate anomalies, the S3 magnetic anomaly over the African fl ank, and the East Coast Magnetic Anomaly ("East Coast Anomaly") over the North American fl ank, are respectively located ~30 km and 180 km inboard of the S1-Blake Spur Magnetic Anomaly pair. Therefore, the ridge jump to the east between "Blake Spur" and "East Coast" anomalies at ~170 Ma theorized by Vogt and others in 1971 is supported by this study. Between the Atlantis and Kane fracture zones, the width of the African Jurassic Magnetic Quiet Zone is ~70 km greater (22%) than the North American Jurassic Magnetic Quiet Zone. Correlatable anomalies exist over the African plate, suggesting a second ridge jump, to the west. Modeling results indicate that this jump occurred between 164 Ma and 159 Ma (Chrons M38 and M32). The ridge jumps can be related to plate interactions as North America separated from Gondwana. However, we note that the second ridge jump occurred approximately at the time suggested for the onset of seafl oor spreading in the Gulf of Mexico.

Birthdate for the Coronation paleocean: age of initial rifting in Wopmay orogen, CanadaThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

“…These results are 10 million years older on average than the 2014.32 ± 0.89 Ma age reported here for the upper Vaillant felsic tuff. The difference in ages is comparable to the time lags of *5, *15, and *10 million years between flood basalt eruptions and the onset of sea-floor spreading in the North, Central and South Atlantic ocean basins, respectively (Bird et al 2007;Eagles 2007;Olesen et al 2007).…”

The Earth expansion theory and its transition from scientific hypothesis to pseudoscientific belief

“…1). Magnetic anomalies (Bird et al, 2007;Korhonen et al, 2007) and age (Heezen and Fornari, 1975;Mueller et al, 1993) maps of the ocean floors show that the ocean basins generated by the fragmentation of Pangea (Atlantic, Indian, and Southern oceans) are axially symmetrical. Every MidOcean Ridge (MOR) runs along the geographical mid-ocean line, and divides two symmetrical sequences of parallel magnetic stripes of gradually increasing age from the MOR to the continent-ocean transition.…”

Tectonic evolution of the Zagros Orogen in the realm of the Neotethys between the Central Iran and Arabian Plates: An ophiolite perspective

“…At this stage, the Neotethys Basin, on account of the Arabian Plate movements caused by the opening of the Atlantic Ocean rift (Stampfli 2000;Bird et al 2007), changed the divergence régime to one of the convergence (Fig. 6).…”