Ten samples of sediments and sedimentary rocks collected during the DSDP (Deep Sea Drilling Project)'s Leg III cruise to South Atlantic were analyzed for oxygen and carbon isotope abundances. These samples include dolomitic chert, Braarudosphaera chalk, stiff pelagic chalk ooze, biosparitic coquina and a white marble near a basalt contact. Although the analyzed values of the oxygen and carbon isotope ratios do not in every instance give a unique answer, they do provide clues and place limitations on speculations regarding the genesis and diagenesis of the samples in question.

The significant conclusions are:

  • 1
    The generation of the Oligocene Braarudosphaera chalk in the South Atlantic was probably related to the upwelling of very cold Antarctic waters.
  • 2
    The biosparitic Cretaceous coquina on the Rio Grande Rise has been cemented under submarine conditions.
  • 3
    The marble between the basalt and overlying ooze is not contact metamorphic, but has been crystallized at a normal deep-marine temperature of about 4.5 °C.