Geology Reference
In-Depth Information
Fig. 10.47.
Hyolithid shells.
A
: cross section.
B
: section along the longest axis. Both photographs show telescoping of
various shells explained by wave transport in nearcoast shallow setting. Uppermost Early Cambrian: Northeastern shore
of the Dead Sea, Jordan. Scale is 1 mm. After Shinaq and Bandel (1992).
J. (1996): Sedimentology and orientation of tentaculite
shells in turbidite lime mudstone to packstone: Lower
Devonian, Barrandian, Bohemia. - Journal of Sedimen-
tary Research,
66
, 888-899
Larsson, K. (1979): Silurian tentaculitids from Gotland and
Scania. - Fossils and Strata,
11
, 1-180
Poijeta, J. (1987): Phylum Hyolitha. - In: Boardman, R.S.,
Cheetham, A.H., Rowell, A.J. (eds.): Fossil invertebrates.
- 416-444, Palo Alto (Blackwell)
Shinaq, R., Bandel, K. (1992): Microfacies of Cambrian lime-
stones in Jordan. - Facies,
27
, 263-284
Tucker, M., Kendall, A.C. (1973): The diagenesis and low-
grade metamorphism of Devonian styliolinid-rich pelagic
carbonates from West Germany: possible analogues of re-
cent pteropod ooze. - Journal of Sedimentary Petrology,
43
, 672-683
Further reading
: K124
or in basins. Tentaculitids can reflect paleocurrent bot-
tom water patterns. Criteria used are frequency distri-
butions on bedding surfaces, or graded bedding, imbri-
cation and abundance of calcisiltite components (tent-
aculites) in the lower parts of turbidite beds (Hladil et
al. 1996). Very small-sized cones will roll downcurrent,
larger cones will point with the apex into the currents.
Presupposing a planktonic life habitat, mass accumu-
lations of dacryoconarids (Pl. 91/3) and styliolinids in
packstones characterize the Standard Microfacies Type
3 common in open-marine deep shelf and basinal set-
tings.
Hyolithids
Other conical shells restricted to the Paleozoic and
most abundant in the Cambrian are included within the
Hyolithida (Fig. 10.47). The group is considered to be
a class of the Mollusca or related to annelid worms.
The probably aragonitic shell is cone- or pyramid-
shaped and was closed by an operculum. Sizes range
between a few millimeters and about 200 mm. The mi-
crostructure corresponds to the crossed-lamellar type.
Hyolithids can be abundant in Cambrian shelf carbon-
ates.
10.2.4.6 Serpulids and Other Worm Tubes
Fossils referred to as worm tubes are known from
throughout the Phanerozoic and common in thin sec-
tions of marine and marginal-marine limestones. These
tubes may be calcareous (Pl. 92/1-8) or agglutinated
(Pl. 92/9, 10). Most calcareous tubes are assigned to
annelid Polychaeta. Annelids are known since the Or-
dovician.
Basics: Tentaculitids, styliolinids and hyolithids
Farsan, N.M. (1994): Tentaculiten: Ontogenese, Systematik,
Phylogenese, Biostratonomie und Morphologie. - Ab-
handlungen der Senckenbergischen naturforschenden Ge-
sellschaft,
547
, 1-128
Fisher, D.W. (1962): Small conoidal shells of uncertain af-
finities - calyptoptomatids. - Treatise on Invertebrate Pa-
leontology, part W, 116-130, Lawrence (Geological Soci-
ety of America)
Hladil, J., Cechan, P., Gabasova, A., Taborsky, Z., Hladikova,
Morphology:
Calcareous worm shells are straight,
curved or spirally coiled unpartioned tubes, a few mil-
limeters in maximum diameter and up to several centi-
meters in maximum length. The tubes consist of Mg-
calcite or aragonite or both. The skeletal mineralogy is
related to mean water temperature. The tubes can form
rock-building gregarious associations (Pl. 92/3, 4) as
