M. N. Bramlette

Coccolithophorids and related nannoplankton of the early Tertiary in California

Evidence of the stratigraphic value of the fossil remains of an abundant and varied calcareous nannoplankton has been limited by little published data. Description of the species and tabulated distributions in 86 samples from a continuous sequence of Paleocene and Eocene strata of California permit recognition of 6 distinct biostratigraphic units. Available evidence on their extension as zones elsewhere and relations to type areas of some European stages are presented.

Pliocene-Pleistocene Boundary in Deep-Sea Sediments

Changes in planktonic microfossil assemblages in Atlantic sediment cores, at approximately the beginning of the Quaternary, correspond in a general way with those recognized in Pacific cores. How closely the horizon marked by these changes approximates to the Pliocene-Pleistocene boundary is not yet established.

The stability of minerals in Sandstone

ABSTRACT Some published data indicate that several minerals, some of which are usually considered relatively stable species, become corroded within fresh and unweathered sandstone strata. This solution or decomposition is evidently due to the action of solutions within the buried strata, and the surficial alteration due to weathering is not included in this discussion. This corrosion of minerals has suggested that some of the less stable ones may have completely disappeared from ancient strata. Examples are presented which show that hornblende and epidote have disappeared from some Miocene sandstones. The mere absence of some relatively unstable mineral, especially some of the ferro-magnesian group, therefore seems doubtful evidence for conclusions regarding the source rocks or the stratigraph c relations of sandstones. These considerations seem especially important for older formations, as the small assemblage of stable minerals, that is usual in early Paleozoic strata, may represent only a survival of the fittest.