Aragonitic Pennsylvanian phylloid algae from New Mexico: The missing link
- Louisiana State Univ., Baton Rouge (United States)
- Univ. of Cambridge (United Kingdom)
Remarkably well-preserved codiacean algae (Eugonophyllum and Anchicodium) retaining original aragonite are present in the Virgilian Holder Formation, Sacramento Mountains, south-central New Mexico. The algae are preserved in a 20-cm-thick packstone between two thick (> 5m) shale beds. Aragonite is preserved as a felt-like mesh of needles in the algal skeletons, in the shell fragments of molluscs, in the walls of sponges, and in botryoidal and isopachous marine cements. The aragonite is confirmed by X-ray diffraction, by visual inspection of pristine aragonite needles with SEM, and by a high content of Sr as revealed by microprobe analysis. The average Sr content of the algae (9,091 ppm, n = 21) is comparable to modern codiaceans. Preservation of internal structure in Eugonophyllum was previously unknown. The medullary (interior) region of the Eugonophyllum thallus is composed of an aragonite felt punctuated by small (20 {mu}m diameter), parallel utricles. As in modern codiaceans, the utricles in the cortical (exterior) region of the thallus increase in diameter and their bulbous tips coalesce to form the outer cortex of the plant. This occurrence provides a key piece of evidence in support of hypotheses concerning the nature and origin of phylloid algal bioherms. Because the internal structure of most fossil phylloid algae is replaced by sparry mosaic calcite, taxonomic classification has been difficult even at the fundamental level of division (phylum). The authors discovery confirms that at least some ancient phylloid algae resembled the modern green algae Halimeda or Udotea, and lends credibility to the suggestion that ancient phylloid algal mounds are analogous to modern Halimeda mounds of the South Pacific.
- OSTI ID:
- 5676783
- Report Number(s):
- CONF-910403-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALGAE
BIOGEOCHEMISTRY
FOSSILS
CHEMICAL COMPOSITION
MOLLUSCS
PROTOZOA
ARAGONITE
CARBONIFEROUS PERIOD
COMPARATIVE EVALUATIONS
EXOSKELETON
GEOLOGIC FORMATIONS
ION MICROPROBE ANALYSIS
ISOTOPE RATIO
MINERALOGY
NEW MEXICO
PALEONTOLOGY
SCANNING ELECTRON MICROSCOPY
STRONTIUM ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS
X-RAY DIFFRACTION
ALKALINE EARTH ISOTOPES
ANIMALS
AQUATIC ORGANISMS
BODY
CARBONATE MINERALS
CHEMICAL ANALYSIS
CHEMISTRY
COHERENT SCATTERING
DEVELOPED COUNTRIES
DIFFRACTION
ELECTRON MICROSCOPY
EVALUATION
FEDERAL REGION VI
GEOCHEMISTRY
GEOLOGIC AGES
INVERTEBRATES
ISOTOPES
MICROANALYSIS
MICROORGANISMS
MICROSCOPY
MINERALS
NONDESTRUCTIVE ANALYSIS
NORTH AMERICA
ORGANS
PALEOZOIC ERA
PLANTS
SCATTERING
SKELETON
USA
580000* - Geosciences