Dilemma of a Cretaceous Time Scale and Rates of Sea-Floor Spreading

Magnetic Anomalies and Seafloor Spreading in the Western North Atlantic, and a Revised Calibration of the Keathly (M) Geomagnetic Reversal Chronology

“…Hays and Pitman (1973) went on to calculate the extra volume of ocean water displaced by these fast-spreading ridges, and attempted to ex¬ plain the great mid-Cretaceous transgressions as a con¬ sequence of rapid spreading. The postulated effect is directly related to the calibration of the Keathley se¬ quence, and has been questioned by some authors (Baldwin et al, 1974;Berggren et al, 1975). If these reversals occurred over a long period, the Cretaceous in¬ terval of normal polarity took less time and the sea¬ floor during this normal interval was generated at a faster rate.…”

An oxygen isotope profile in a section of Cretaceous oceanic crust, Samail Ophiolite, Oman: Evidence for δ18O buffering of the oceans by deep (>5 km) seawater‐hydrothermal circulation at mid‐ocean ridges

“…[Larson and Pitman, 1972]. Such a rate is based upon extrapolating rates determined on small segments of preserved seafloor to the entire ridge system, as well as assuming that the overall ridge length is equivalent to the present-day value; thus 12 km2/yr may be too high for any reasonable Phanerozoic worldwide rate [Baldwin et al, 1974;Berger and Winterer, 1974].…”

“…• is the w/r ratio (in oxygen units) for the bulk system, deduced from heat flow arguments, and 12 km2/yr is chosen as a plausible upper limit for spreading rates. Although the latter rate has been proposed for some portions of Cretaceous ocean floor, extrapolation of such high rates to a worldwide rate is very controversial[Baldwin et al, 1974]. However, a rate approaching this magnitude conceivably could apply to the Archean.…”

A palaeomagnetic study of the Upper Mesozoic succession in Northern Tunisia

“…Some time ago, Baldwin, Coney & Dickinson (1974) discussed the indeterminacy of the Cretaceous marine magnetic anomaly scale, with particular reference to the Cretaceous quiet (normal) period. This indeterminacy was resolved by the analysis of Irving & Pullaiah (1976) and confirmed by the version of the analysis used here.…”