Hostname: page-component-586b7cd67f-t7fkt Total loading time: 0 Render date: 2024-11-27T11:16:12.602Z Has data issue: false hasContentIssue false
  • English
  • Français

Probable calcified metaphytes in the latest Proterozoic Nama Group, Namibia: origin, diagenesis, and implications

Published online by Cambridge University Press:  14 July 2015

S. W. F. Grant ,
A. H. Knoll  and
G. J. B. Germs
S. W. F. Grant
Affiliation:
1Botanical Museum, Harvard University, Cambridge, Massachusetts 02138
A. H. Knoll
Affiliation:
1Botanical Museum, Harvard University, Cambridge, Massachusetts 02138
G. J. B. Germs
Affiliation:
2J. C. I. Research Unit, P.O. Box 976, 1760 Randfontein, South Africa
Get access Rights & Permissions [Opens in a new window]

Abstract

Samples from the Huns Limestone Member, Urusis Formation, Nama Group, at two adjacent localities in southern Namibia contain thin foliose to arched, sheet-like carbonate crusts that are 100–500 µm thick and up to 5 cm in lateral dimension. Morphologic, petrographic, and geochemical evidence supports the interpretation of these delicate crusts as biogenic, most likely the remains of calcified encrusting metaphytes. The original sediments of the fossiliferous samples contained aragonitic encrusting algae, botryoidal aragonite cements, and an aragonite mud groundmass. Spherulites within the precursor mud could represent bacterially induced mineral growths or the concretions of marine rivularian cyanobacteria. Original textures were severely disrupted during the diagenetic transition of aragonite to low-magnesian calcite, but some primary structures remain discernible as ghosts in the neomorphic mosaic. Gross morphology, original aragonite mineralogy, and hypobasal calcification indicate that the crusts are similar to late Paleozoic phylloid algae and extant peyssonnelid red algae. Structures interpreted as possible conceptacles also suggest possible affinities with the Corallinaceae.

Two species of Cloudina, interpreted as the remains of a shelly metazoan, are also known from limestones in the Nama Group. It is possible, therefore, that skeletalization in metaphytes and animals arose nearly simultaneously near the end of the Proterozoic Eon.

Type
Research Article
Information
Journal of Paleontology , Volume 65 , Issue 1 , January 1991 , pp. 1 - 18
Copyright
Copyright © The Journal of Paleontology 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Allan, J. R., and Matthews, R. K. 1982. Isotope signatures associated with early meteoric diagenesis. Sedimentology 29:797–817.Google Scholar
Allsopp, H. L., Welke, H., Kostlin, E. O., Burger, A. J., Kröner, A., and Blignault, H. J. 1979. Rb–Sr and U–Pb geochronology of late Precambrian–early Paleozoic igneous activity in the Richtersveld and southern South West Africa. Geological Society of South Africa, Transactions and Proceedings, 82:185–204.Google Scholar
Andrews, J. E. 1986. Microfacies and geochemistry of Middle Jurassic algal limestones from Scotland. Sedimentology, 33:499–520.Google Scholar
Awramik, S. K. 1971. Precambrian columnar stromatolite diversity: reflection of metazoan appearance. Science, 174:825–827.Google Scholar
Bathurst, R. G. C. 1964. The replacement of aragonite by calcite in the molluscan shell wall, p. 357–376. In Imbrie, J. and Newell, N. D. (eds.), Approaches to Paleoecology. Wiley, New York.Google Scholar
Bathurst, R. G. C. 1975. Carbonate Sediments and their Diagenesis. Elsevier, New York, 658 p.Google Scholar
Bathurst, R. G. C. 1982. Genesis of stromatactis cavities between submarine crusts in Palaeozoic carbonate mud buildups. Journal of the Geological Society of London, 139:165–181.Google Scholar
Bathurst, R. G. C. 1983. Neomorphic spar versus cement in some Jurassic grainstones: significance for evaluation of porosity evolution and compaction. Journal of the Geological Society of London, 140:229–237.Google Scholar
Beeunas, M. A., and Knauth, L. P. 1985. Preserved stable isotopic signature of subaerial diagenesis in the 1.2–b.y. Mescal Limestone, central Arizona: implications for the timing and development of a terrestrial plant cover. Geological Society of America Bulletin, 96:737–745.Google Scholar
Beier, J. A. 1987. Petrographic and geochemical analysis of caliche profiles in a Bahamian Pleistocene dune. Sedimentology, 34:991–998.Google Scholar
Braithwaite, C. J. R., Casanova, J., Frevertand, T., and Whitton, B. A. 1989. Recent stromatolites in landlocked pools on Aldabra, western Indian Ocean. Palaeogeography, Palaeoclimatology, Palaeo-ecology, 69:145–165.Google Scholar
Brand, U. 1989. Aragonite–calcite transformation based on Pennsylvanian molluscs. Geological Society of America Bulletin, 101:377–390.Google Scholar
Brand, U., and Morrison, J. O. 1987. Biogeochemistry of fossil marine invertebrates. Geoscience Canada, 14:85–107.Google Scholar
Brand, U., and Veizer, J. 1980. Chemical diagenesis of a multicomponent carbonate system—1: trace elements. Journal of Sedimentary Petrology, 50:1219–1236.Google Scholar
Brasier, M. D. 1989. Towards a biostratigraphy of the earliest skeletal biotas, p. 117–165. In Cowie, J. W. and Brasier, M. D. (eds.), The Precambrian–Cambrian Boundary. Clarendon Press, Oxford.Google Scholar
Brooke, C. 1986. Calcareous algae and algal limestones from the Silurian of Gotland, Sweden. Unpubl. Ph.D. thesis, University of Wales, Cardiff, 247 p.Google Scholar
Buchbinder, B., Begin, Z. B., and Friedman, G. M. 1974. Pleistocene alga tufa of Lake Lisan, Dead Sea area, Israel. Israel Journal of Earth-Sciences, 23:131–138.Google Scholar
Budd, D. A. 1988. Aragonite–calcite transformation during fresh-water diagenesis of carbonates: insights from pore-water chemistry. Geological Society of America Bulletin, 100:1260–1270.Google Scholar
Butterfield, N. J., Knoll, A. H., and Swett, K. 1988. Exceptional preservation of fossils in an upper Proterozoic shale. Nature, 334:424–427.Google Scholar
Cabioch, J., and Giraud, G. 1986. Structural aspects of biomineralization in the coralline algae (calcified Rhodophyceae), p. 141–156. In Leadbeater, B. S. C. and Riding, R. (eds.), Biomineralization in Lower Plants and Animals. The Systematics Association, Clarendon Press, Oxford.Google Scholar
Conway Morris, S., and Jenkins, R. J. F. 1986. Healed injuries in Early Cambrian trilobites from South Australia. Alcheringa, 9:167–177.Google Scholar
Conway Morris, S., Mattes, B. W., and Menge, Chen. 1990. The early skeletal organism Cloudina: new occurrences from Oman and possibly China. American Journal of Science, 290-A:245–260.Google Scholar
Crimes, T. P., and Germs, G. J. B. 1982. Trace fossils from the Nama Group (Precambrian–Cambrian) of Southwest Africa (Namibia). Journal of Paleontology, 56:890–907.Google Scholar
Cross, T. A., and Klosterman, M. J. 1981. Primary submarine cements and neomorphic spar in a stromatolitic bound phylloid algal bioherm, Laborcita Formation (Wolfcampian), Sacramento Mountains, New Mexico, U.S.A., p. 60–73. In Monty, C. (ed.), Phanerozoic Stromatolites. Springer-Verlag, Berlin.Google Scholar
Davies, P. J., Bubela, B., and Ferguson, J. 1978. The formation of ooids. Sedimentology, 25:703–730.Google Scholar
Denizot, M. 1968. Les Algues Floridees Encruoutantes (a l'exclusion des Corallinaecees). Laboratoire de Cryptogamie, Museum National d'Histoire Naturelle, Paris, 310 p.Google Scholar
Dravis, J. J., and Yurewicz, D. A. 1985. Enhanced carbonate petrography using fluorescence microscopy. Journal of Sedimentary Petrology, 55:795–804.Google Scholar
Drew, G. H. 1914. On the precipitation of calcium carbonate in the sea by marine bacteria, and on the action of denitrifying bacteria in tropical and temperate seas. Papers from the Tortugas Laboratory, Carnegie Institution of Washington Publication, 182:7–45.Google Scholar
Droser, M. L., and Bottjer, D. J. 1988. Trends in depth and extent of bioturbation in Cambrian carbonate marine environments, western United States. Geology, 16:233–236.Google Scholar
Du, Rulin, Lifu, Tian, and Hanbang, Li. 1986. Discovery of Megafossils in the Gaoyuzhuang Formation of the Changchungian System, Jixian. Acta Geologica Sinica, 198:118–120.Google Scholar
Ferguson, J., Bubela, B., and Davies, P. J. 1978. Synthesis and possible mechanism of formation of radial carbonate ooids. Chemical Geology, 22:285–308.Google Scholar
Frank, J. R., Carpenter, A. B., and Oglesby, T. W. 1982. Catho-doluminescence and composition of calcite cement in the Tam Sauk Limestone (Upper Cambrian), southeast Missouri. Journal of Sedimentary Petrology, 52:631–638.Google Scholar
Friedman, G. M. 1964. Early diagenesis and lithification in carbonate sediments. Journal of Sedimentary Petrology, 34:777–813.Google Scholar
Germs, G. J. B. 1972a. The stratigraphy and paleontology of the lower Nama Group, South West Africa. University of Cape Town Chamber of Mines, Precambrian Research Unit, Bulletin, 12, 250 p.Google Scholar
Germs, G. J. B. 1972b. New shelly fossils from the Nama Group, South West Africa. American Journal of Science, 272:752–761.Google Scholar
Germs, G. J. B. 1973. A reinterpretation of Rangea schneiderhoehni and the discovery of a related new fossil from the Nama Group, South West Africa. Lethaia 6:1–9.Google Scholar
Germs, G. J. B. 1983. Implications of a sedimentary facies and depositional environmental analysis of the Nama Group in South West Africa/Namibia. The Geological Society of South Africa, Special Publication, 11:89–114.Google Scholar
Germs, G. J. B., Knoll, A. H., and Vidal, G. 1986. Latest Proterozoic microfossils from the Nama Group, Namibia (South West Africa). Precambrian Research, 32:45–62.Google Scholar
Glaessner, M. F. 1976. Early Phanerozoic annelid worms and their geological and biological significance. Journal of the Geological Society of London, 132:259–275.Google Scholar
Glaessner, M. F. 1984. The Dawn of Animal Life: A Biohistorical Study. Cambridge University Press, Cambridge, 244 p.Google Scholar
Glaessner, M. F., and Wade, M. 1966. The late Precambrian fossils from Ediacara, South Australia. Paleontology, 9:599–628.Google Scholar
Golubic, S., and Campbell, S. E. 1981. Biogenically formed aragonite concretions in marine Rivularia , p. 209–229. In Monty, C. (ed.), Phanerozoic Stromatolites. Springer-Verlag, Berlin.Google Scholar
Grant, S. W. F. 1989. Shell structure, life habit and global distribution of Cloudina . Geological Association of Canada and Mineralogical Association of Canada, Program with Abstracts, 14:A100–A101.Google Scholar
Grant, S. W. F. 1990. Shell structure and distribution of Cloudina, a potential index fossil for the terminal Proterozoic. American Journal of Science, 290-A:261–294.Google Scholar
Grant, S. W. F., Knoll, A. H., and Germs, G. J. B. 1987. Metaphyte biomineralization in the uppermost Proterozoic Nama Group, Namibia. Geological Society of America, Abstracts with Programs, 19:681.Google Scholar
Grey, K., and Williams, I. R. 1990. Problematic bedding-plane markings from the Middle Proterozoic Manganese Subgroup, Bangamall Basin, western Australia. Precambrian Research, 46:307–327.Google Scholar
Gürich, G. 1933. Die Kuibis-Fossilien der Nama Formation von Südwest Afrika. Palaeontologische Zeitschrift, 15:137–154.Google Scholar
Hahn, G., and Pflug, H. D. 1985. Die Cloudinidae n. fam., Kalk-Röhren aus dem Vendium und Unter-Kambrium. Senckenbergiana Lethaea, 65:413–431.Google Scholar
Hemming, G. N., Meyers, W. J., and Grams, J. C. 1989. Cathodo-luminescence in diagenetic calcites: the roles of Fe and Mn as deduced from electron probe and spectrophotometric measurements. Journal of Sedimentary Petrology, 59:404–411.Google Scholar
Hofmann, H. J. 1985. The mid-Proterozoic Little Dal macrobiota, Mackenzie Mountains, north-west Canada. Palaeontology, 28:331–354.Google Scholar
Hofmann, H. J., and Aitken, J. D. 1979. Precambrian biota from the Little Dal Group, Mackenzie Mountains, northwest Canada. Canadian Journal of Earth Sciences, 16:150–166.Google Scholar
Hofmann, H. J., and Jinbiao, C. 1981. Carbonaceous megafossils from the Precambrian (1800 Ma) near Jixian, northern China. Canadian Journal of Earth Sciences, 18:443–447.Google Scholar
Holland, H. D. 1978. The Chemistry of the Atmosphere and Ocean. John Wiley and Sons, New York, 351 p.Google Scholar
Horodyski, R. J. 1982a. Impressions of algal mats from the Middle Proterozoic Belt Supergroup, northwestern Montana, U.S.A. Sedimentology, 29:285–289.Google Scholar
Horodyski, R. J. 1982b. Problematic bedding-plane markings from the middle Proterozoic Appekunny Argillite, Belt Supergroup, northwestern Montana. Journal of Paleontology, 56:882–889.Google Scholar
Horodyski, R. J., and Mankiewiez, C. 1990. Possible Late Proteozoic skeletal algae from the Pahrump Group, Kingston Range, southeastern California. American Journal of Science, 290A:149–169.Google Scholar
Horstmann, U. E. 1987. Die metamorphe Entwicklung im Damara Orogen, Südwest Afrika/Namibia, abgeleitet aus K/Ar-Datierungen an detritischen Hellglimmern aus Molassessedimenten der Nama Group. Göttinger Arbeiten zur Geologie and Paläontologie, 32, 95 p.Google Scholar
Hudson, J. D. 1962. Pseudo-pleochroic calcite in recrystallized shelllimestones. Geological Magazine, 99:492–500.Google Scholar
Husseini, S. I., and Matthews, R. K. 1972. Distribution of high-magnesium calcite in lime muds of the Great Bahama Bank: diagenetic implication. Journal of Sedimentary Petrology, 42:179–182.Google Scholar
James, N. P. 1972. Holocene and Pleistocene calcareous crust (caliche) profiles: criteria for subaerial exposure. Journal of Sedimentary Petrology, 42:817–836.Google Scholar
James, N. P., and Ginsburg, R. N. 1979. The seaward margin of Belize barrier and atoll reefs. International Association of Sedimentologists, Special Publication 3, 191 p.Google Scholar
James, N. P., Wray, J. L., and Ginsburg, R. N. 1984. Calcification of encrusting aragonitic algae: implications for origin of late Paleozoic reefs and cements. American Association of Petroleum Geologists Bulletin 68:491.Google Scholar
James, N. P., Wray, J. L., and Ginsburg, R. N. 1988. Calcification of encrusting aragonitic algae (Peyssonneliaceae): implications for the origin of late Paleozoic reefs and cements. Journal of Sedimentary Petrology, 58:291–303.Google Scholar
Jenkins, R. J. F. 1985. The enigmatic Ediacaran (late Precambrian) genus Rangea and related forms. Paleobiology, 11:336–355.Google Scholar
Jenkins, R. J. F., and Gehling, J. G. 1978. A review of the frond-like fossils of the Ediacara assemblage. Records of the South Australia Museum, 17:347–359.Google Scholar
Johnson, J. H. 1956. Archaeolithophyllum, a new genus of Paleozoic coralline algae. Journal of Paleontology, 30:53–55.Google Scholar
Johnson, J. H. 1961. Limestone-Building Algae and Algal Limestones. Colorado School of Mines, Johnson Publishing Co., Boulder, Colorado, 297 p.Google Scholar
Kaufman, A. J., Hayes, J. M., Knoll, A. H., and Germs, G. J. B. 1988. Secular variations of carbon isotope ratios in whole rock and micritic phases of carbonates from upper Proterozoic successions in Namibia. Terra Cognita, 8:218.Google Scholar
Kaufman, A. J., Hayes, J. M., Knoll, A. H., and Germs, G. J. B. In press. Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism. Precambrian Research.Google Scholar
Konishi, K., and Wray, J. L. 1961. Eugonophyllum, a new Pennsylvanian and Permian algal genus. Journal of Paleontology, 35:659–666.Google Scholar
Kröner, A., and Clauer, N. 1979. Isotopic dating of low-grade metamorphic shales in northern Namibia (South West Africa) and implications for the orogenic evolution of the Pan–African Damara Belt. Precambrian Research 10:59–72.Google Scholar
Kröner, A., McWilliams, M. O., Germs, G. J. B., Reid, A. B., and Schalk, K. E. L. 1980. Paleomagnetism of late Precambrian to early Paleozoic mixtite-bearing formations in Namibia (South West Africa): the Nama Group and Blaubeker Formation. American Journal of Science, 280:942–968.Google Scholar
Krumbein, W. E. 1974. On the precipitation of aragonite on the surface of marine bacteria. Naturwissenschaften, 61:167.Google Scholar
Lasemi, Z., and Sandberg, P. A. 1983. Recognition of original mineralogy in micrites. American Association of Petroleum Geologists Bulletin, 67:499–500.Google Scholar
Lasemi, Z., and Sandberg, P. A. 1984. Transformation of aragonite dominated lime muds to microcrystalline limestones. Geology, 12:420–423.Google Scholar
Lasemi, Z., and Boardman, R. 1990. New microtextural criterion for differentiation of compaction and early cementation in fine-grained limestones. Geology, 18:370–373.Google Scholar
Lewis, S. M. 1986. The role of herbivorous fishes in the organization of a Caribbean reef community. Ecological Monographs, 56:183–200.Google Scholar
Lohmann, K. C., and Meyers, W. J. 1978. Microdolomite inclusions in cloudy prismatic calcites: a proposed criterion for former high magnesium calcites. Journal of Sedimentary Petrology, 47:1078–1088.Google Scholar
Lowenstam, H. A., and Weiner, S. 1989. On biomineralization, p. 227–251. Oxford University Press, New York.Google Scholar
Mason, R. A. 1987. Ion microprobe analysis of trace elements in calcite with an application to the cathodoluminescence zonation of limestone cements from the Lower Carboniferous of South Wales, U.K. Chemical Geology, 64:209–224.Google Scholar
Massieux, M., and Denizot, M. 1964. Rapprochement de genre Pseudolithothamnion Pfonder avec le genre actuel Ethelia Weber van Bosse (Algues Florideae, Squamariaceae). Revue de Micropaleontologie, 7:31–42.Google Scholar
McMenamin, M. A. S. 1986. The garden of Ediacara. Palaios, 1:178–182.Google Scholar
Monaghan, P. H., and Lytle, M. L. 1956. The origin of calcareous ooliths. Journal of Sedimentary Petrology, 26:111–118.Google Scholar
Monty, C. L. V. 1976. The origin and development of cryptalgal fabrics, p. 193–249. In Walter, M. R. (ed.), Stromatolites. Elsevier, New York.Google Scholar
Morita, R. Y. 1980. Calcite precipitation by marine bacteria. Geomicrobiology Journal, 2:63–82.Google Scholar
Novitsky, J. A. 1981. Calcium carbonate precipitation by marine bacteria. Geomicrobiology Journal, 2:375–388.Google Scholar
Oppenheimer, C. H. 1961. Note on the formation of spherical aragonitic bodies in the presence of bacteria from the Bahama Bank. Geochimica et Cosmochimica Acta, 23:295–296.Google Scholar
Pflug, H. D. 1970a. Zur Fauan der Nama-Schichten in Südwest-Afrika. I. Pteridinia, Bau und systematische Zugehörigkeit. Palaeontographica, Abteilung A, 134:226–262.Google Scholar
Pflug, H. D. 1970b. Zur Fauna der Nama-Schichten in Südwest-Afrika. II. Rangidae, Bau und systematische Zugehörigkeit. Palaeontographica, Abteilung A, 135:198–231.Google Scholar
Pflug, H. D. 1972a. Zur Fauna der Nama-Schichten in Südwest-Afrika. III. Erniettomorpha, Bau und Systematik. Palaeontographica, Abteilung A, 139:134–170.Google Scholar
Pflug, H. D. 1972b. Systematik der jung-präkambrischen Petalonamae Pflug 1970. Paläontologische Zeitschrift, 46:56–67.Google Scholar
Pingitore, N. E. 1976. Vadose and phreatic diagenesis: processes products and their recognition in corals. Journal of Sedimentary Petrology, 46:985–1006.Google Scholar
Pray, L. C., and Wray, J. L. 1963. Porous algal facies (Pennsylvanian) Honaker Trail, San Juan Canyon, Utah, p. 204–234. In Shelf Carbonates of the Paradox Basin. Four Corners Geological Society Symposium, 4th Field Conference.Google Scholar
Reid, P. R. 1986. Discovery of Triassic phylloid algae: possible links with the Paleozoic. Canadian Journal of Earth Sciences, 23:2068–2071.Google Scholar
Riding, R., and Voronova, L. 1984. Assemblages of calcareous algae near the Precambrian/Cambrian boundary in Siberia and Mongolia. Geological Magazine, 121:205–210.Google Scholar
Sandberg, P. A. 1984. Recognition criteria for calcitized skeletal and non-skeletal aragonites. Palaeontographica Americana, 54:272–281.Google Scholar
Sandberg, P. A. 1985. Aragonite cements and their occurrence in ancient limestones, p. 33–57. In Scheidermann, N. and Harris, P. M. (eds.), Carbonate Cements. Society of Economic Paleontologists and Mineralogists, Tulsa, Oklahoma.Google Scholar
Santrock, J., Studley, S. A., and Hayes, J. M. 1985. Isotopic analyses based on the mass spectrum of carbon dioxide. Analytical Chemistry, 57:1444–1448.Google Scholar
Scholle, P. A., and Kinsman, D. J. J. 1974. Aragonitic and high-Mg calcite caliche from the Persian Gulf—a modern analog for the Permian of Texas and New Mexico. Journal of Sedimentary Petrology, 44:904–916.Google Scholar
Schroeder, J. H. 1972. Fabrics and sequences of submarine carbonate cements in Holocene Bermuda cup reefs. Geologische Rundshau, 61:708–730.Google Scholar
Siedlecka, A. 1978. Late Precambrian tidal-flat deposits and algal stromatolites in the Båtsfjord Formation, East Finmark, North Norway. Sedimentary Geology, 21:277–310.Google Scholar
Smart, P. L., Dawans, J. M., and Whitaker, F. 1988. Carbonate dissolution in a modern mixing zone. Nature, 335–811–813.Google Scholar
Steneck, R. S. 1983. Escalating herbivory and resulting adaptive trends in calcareous algal crusts. Paleobiology, 9:44–61.Google Scholar
Steneck, R. S. 1985. Adaptations of crustose coralline algae to herbivory patterns in space and time, p. 352–366. In Toomey, D. F. and Nitecki, M. H. (eds.), Paleoalgology: Contemporary Research and Applications. Springer-Verlag, Berlin.Google Scholar
Steneck, R. S. 1986. The ecology of coralline algal crusts: convergent patterns and adaptive strategies. Annual Review of Ecology and Systematics, 17:273–303.Google Scholar
Stoessell, R. K., Ward, W. C., Ford, B. H., and Schuffert, J. D. 1989. Water chemistry and CaCO3 dissolution in the saline part of an open-flow mixing zone, coastal Yucatan Peninsula, Mexico. Geological Society of America Bulletin, 101:159–169.Google Scholar
Vaughan, T. W. 1914. Preliminary remarks on the geology of the Bahamas, with special reference to the origin of the Bahaman and Floridian oölites. Papers from the Tortugas Laboratory, Carnegie Institution Washington Publication, 182:47–54.Google Scholar
Veizer, J. 1983. Chemical diagenesis of carbonates: theory and application of trace element technique, p. (3)1–(3)100. In Arthur, M. A. (organizer), Stable Isotopes in Sedimentary Geology. Society of Economic Paleontologists and Mineralogists Short Course Notes, 10.Google Scholar
Vermeij, G. J. 1989. The origin of skeletons. Palaios, 4:585–589.Google Scholar
Wachter, E. A., and Hayes, J. M. 1985. Exchange of oxygen isotopes in carbon dioixde-phosphoric acid systems. Chemical Geology (Isotope Geosciences Section), 52:365–374.Google Scholar
Wallace, M. W. 1987. The role of internal erosion and sedimentation in the formation of stromatactis mudstones and associated lithologies. Journal of Sedimentary Petrology, 57:695–700.Google Scholar
Walter, M. R., Oehler, J. H., and Oehler, D. Z. 1976. Megascopic algae 1300 million years old from the Belt Supergroup, Montana: a reinterpretation of Walcott's Helminthoidichnites . Journal of Paleontology, 50:872–881.Google Scholar
Wood, A. 1944. Organs of reproduction in the Solenoporaceae. Proceedings of the Geologists' Association, 55:107–113.Google Scholar
Wray, J. L. 1964. Archaeolithophyllum, an abundant calcareous alga in limestones of the Lansing Group (Pennsylvanian) southeastern Kansas. Kansas Geological Survey Bulletin, 170, Pt. 1, 13 p.Google Scholar
Wray, J. L. 1977. Calcareous Algae. Developments in Palaeontology and Stratigraphy, 4. Elsevier, New York, 185 p.Google Scholar
Wray, J. L., James, N. P., and Ginsburg, R. N. 1974. The puzzling Paleozoic phylloid algae—Holocene answer in squamariacean calcareous red algae. American Association of Petroleum Geologists, Annual Meeting, 2:82–83.Google Scholar
Yun, Zhang. 1989. Multicellular thallophytes with differentiated tissues from late Proterozoic phosphate rocks of South China. Lethaia, 22:113–132.Google Scholar