GRAINS: Skeletal Fragments: Vertebrate and Plant Remains
2003. "GRAINS: Skeletal Fragments: Vertebrate and Plant Remains", A Color Guide to the Petrography of Carbonate Rocks: Grains, textures, porosity, diagenesis, Peter A. Scholle, Dana S. Ulmer-Scholle
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Phylum Chordata, subphylum Vertebrata
Vertebrates range from Cambrian to Recent (initially as jawless fish)
Jawed vertebrates — Early Silurian-Recent
Terrestrial vertebrates — (Late Devonian) Carboniferous-Recent
Reptiles — Carboniferous-Recent
Early vertebrate remains (Cambrian-Silurian) are confined to marine settings; subsequent diversification led to expansion into virtually all environments from polar to tropical and from terrestrial to abyssal marine. Most vertebrate remains in carbonate rocks are fish scales and teeth from lacustrine or marine settings; bone and tooth material from other groups, however, also can be found on occasion.
Vertebrate remains are rare but can sometimes be found concentrated by wave or current action or by nonsedimentation of other materials at hiatus surfaces.
Bones and teeth are largely composed of organic proteins (mainly collagen) and calcium phosphate (carbonatehydroxylapatite, sometimes termed collophane when it is microcrystalline). The interior parts of bones (the cancellous portions) have a spongy texture that commonly is filled with precipitated cement (most commonly carbonate, silica or phosphate) during diagenesis.
Vertebrate organisms have an enormous range of external morphologies, but all have a vertebral column and other hard parts (other bones, teeth, or scales) that typically disarticulate upon death and can become scattered into carbonate and noncarbonate sedimentary deposits.
Vertebrate debris can range in size from less than a mm to well over 1 m, but is typically in the mm to cm size range.
Most bones share common features: a dense, smooth, outer or cortical part, and an interior composed of multiple layers of porous or spongy, cancellous material (in life, the porous areas are occupied by marrow).
Teeth are constructed of three layers: a pulpy cavity, a covering of dentine, and where the tooth is exposed, an additional covering of enamel.
Dentine is relatively hard and dense and has a mineral content of about 75%; enamel is even denser and is almost 98% hydroxylapatite.
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