GRAINS: Skeletal Fragments: Annelids and Related Groups
2003. "GRAINS: Skeletal Fragments: Annelids and Related Groups", A Color Guide to the Petrography of Carbonate Rocks: Grains, textures, porosity, diagenesis, Peter A. Scholle, Dana S. Ulmer-Scholle
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Worm remains are known from Precambrian to Recent — most are soft-bodied, but preserved fossil forms include some segmented worms that built solid housing structures. These generally belong to the:
Phylum Annelida: Proterozoic-Recent
Class Polychaeta: (Proterozoic?) Cambrian-Recent
The most important sediment-producing or sediment-influencing groups in Phylum Annelida include three groups or families within the order Sabellida:
Serpulids and spirorbids (groups that precipitate solid calcareous tubes)
Sabellariids (producers of agglutinated tubes)
A variety of soft-bodied burrowers and pellet producers
Most preserved forms lived in fully marine to hypersaline-water settings; rare in freshwater and even rarer in terrestrial settings (although non-calcified forms can produce pellets in those environments).
Serpulids are most common in shallow to coastal waters (largely as hard-substrate encrusters) but extend into deeper shelf waters as well. Especially common in slightly hypersaline settings (where they may form small reef-like masses) or at hiatus surfaces.
Figures & Tables
A Color Guide to the Petrography of Carbonate Rocks: Grains, textures, porosity, diagenesis
This volume expands and improves the AAPG 1978 classic, A Color Illustrated Guide to Carbonate Rock Constituents, Textures, Cements, and Porosities(AAPG Memoir 27). Carbonate petrography can be quite complicated. Changing assemblages of organisms through time, coupled with the randomness of thin-section cuts through complex shell forms, add to the difficulty of identifying skeletal grains. Furthermore, because many primary carbonate grains are composed of unstable minerals (especially aragonite and high-Mg calcite), diagenetic alteration commonly is quite extensive in carbonate rocks. The variability of inorganic and biogenic carbonate mineralogy through time, however, complicates prediction of patterns of diagenetic alteration. This book is designed to help deal with such challenges. It includes a wide variety of examples of commonly encountered skeletal and nonskeletal grains, cements, fabrics, and porosity types. It includes extensive new tables of age distributions, mineralogy, morphologic characteristics, environmental implications and keys to grain identification. It also encompasses a number of noncarbonate grains, that occur as accessory minerals in carbonate rocks or that may provide important biostratigraphic or paleoenvironmental information in carbonate strata. With this guide, students and other workers with little formal petrographic training should be able to examine thin sections or acetate peels under the microscope and interpret the main rock constituents and their depositional and diagenetic history.
- carbonate rocks
- color imagery
- problematic fossils
- sedimentary rocks