Significance of Palynomorphs as Sedimentation Indicators in Cretaceous Straight Cliffs Sandstone, Utah: ABSTRACT

Abstract

Palynomorphs, which are abundant in maceration residues of many fine-grained clastic rocks, commonly include spore and pollen exines, waxy cuticles, resinous bodies, and vitrinized and fusinized material which is incorporated with mineral grains in sediments. Differences in occurrence and relative abundance of the palynomorphs may be attributed to differential response of the particles to transport and sedimentation because of these parameters: (1) size: range from silt to fine sand; (2) shape: spheroidal, ovoidal, irregular, tabular, platy, or bladdered; (3) specific gravity: range from about 1.2 to 1.6. Interpretation of the sedimentary environment of the Upper Cretaceous Straight Cliffs Sandstone is based on application of results of studies of the palynology of several modern sedimentary areas, specifically by comparison of fossil and modern palynomorph residues. The following patterns are indicated for the paralic Straight Cliffs Sandstone: 1. In nearshore neritic beds, species of displaced terrigenous plants are numerous, marine microplankton abundant, resinous bodies and cuticles less abundant, and sorting poor. Apparently, once carried into the site of deposition, organic particles were winnowed little by offshore currents. End_Page 734------------------------------ 2. In nearshore continental beds, species of microfossils are less numerous generally; many beds contain mainly one kind of palynomorph, such as resinous bodies or fusinized material. Possibly this reflects local conditions which favor minimum particle transport and mixing. 3. Bladdered pollen grains occur in varying abundance in almost every bed regardless of other palynomorph abundance. Differing hydrodynamic response of these large grains may govern their anomalous occurrence, in contrast to smaller nonbladdered forms. End_of_Article - Last_Page 735------------