Abstract Many clastic terrigenous rocks contain variable, but in some cases substantial, amounts of primarily nondetrital constituents. These include biogenic/skeletal grains such as calcareous shells, siliceous tests, phosphatic vertebrate or invertebrate material and organic matter (from plant remains down to plankton and microbial filaments). Nonskeletal, but still biogenic grains, primarily fecal pellets, also can be abundant in some deposits, especially bioturbated ones. Other materials, such as phosphate, gypsum, green marine clays (glauconite, berthierine, chamosite) and ferrous oxides and hydroxides, are found in terrigenous deposits as minerals formed by direct precipitation, through alteration of other minerals or as detrital grains. Most of these grains, in some circumstances, can be sufficiently abundant to be the major constituents of rocks. Even where such grains are not the major rock constituent, however, it is important to recognize them and, if deemed important, one can add a descriptive adjective to any rock name (e.g., glauconitic quartz arenite or radiolarian-bearing arkosic siltstone).

Abstract Often grouped with the tintinnids (pelagic ciliate protozoans of the subclass Spirotheca), although modern tintinnids are organic-walled and calpionellids had calcareous walls. Thus, calpionellids are grouped by other workers as Protozoa incertae sedis . Calpionellids — Late Jurassic (Tithonian) to Early Cretaceous (Valanginian; possibly into Albian) Tintinnids — Jurassic-Recent (but with possible record extending into the Paleozoic, perhaps even to the Cambrian) These open marine organisms are significant contributors to pelagic limestones and chalks in the Late Jurassic. Their distribution is largely restricted to the warm-water Tethyan region, within about 30-35° of the paleoequator. All calpionellids apparently were composed of low-magnesium calcite; thus, generally well preserved. The TEM studies conducted by Fischer et al. (1967; cited at end of book’s introduction) showed that some calpionellids built two-layered tests in which the main layer incorporated carbonate detritus (including coccoliths) and was lined by an inner, secreted layer. Small size (typically 45 to 150 μ m in length and 30 to 90 μ m in width), spherical to elongate, U- or V-shaped grains with a large opening rimmed, in some cases, by a narrowed, slightly thickened collar.