Magnetic susceptibility dataset from the early Givetian to early Frasnian in the La Thure section

Recent advances in radiometric dating result in significant improvements in the geological timescale and provide better insight into the timing of various processes and evolutions within the Earth's system. However, no radiometric ages are contained within the Givetian. Consequently, the absolute ages of the Givetian Stage boundaries, as well as the stage's duration, remain poorly constrained. As an alternative, the analysis of sedimentary cycles allows for the estimation of the duration of this stage. We examined the high-resolution magnetic susceptibility signals of four Givetian outcrops in the Givet area for a possible astronomical imprint, to fully understand the rates of evolutionary and environmental change. All four sections are firmly correlated and wavelet analyses of the magnetic susceptibility signals reveal the imprint of astronomical eccentricity forcing. The highly stable 405 kyr cycles constrain the duration of the Givetian Stage at 4.35±0.45 Myr, which is in good agreement with the International Chronostratigraphic Chart (5.0 Myr). The studied sections also exhibit an imprint of obliquity, suggesting a climatic teleconnection between low and high latitudes. The corresponding microfacies curves demonstrate similar astronomical imprint, and thereby indicate that the observed 10**5 year-scale cyclicity is the result of climatic and environmental change.

Clay minerals at DSDP Sites 71-511 and 71-513

The distribution of clay minerals, determined by X-ray diffraction, is given for Jurassic to Holocene sediments recovered at DSDP Sites 511 and 513 in the Southwest Atlantic. These data, plus the lithologic and paleoenvironmental information gathered by the shipboard scientists, are used to subdivide the sedimentary sequence into genetic lithologic facies labeled series, seven for Site 511 and two for Site 513. Sediments of these series reflect the main historical and paleoenvironmental events which other means of study have determined to affect this region; particularly important was the opening of the South Atlantic during the Early Cretaceous.