Geology Reference
In-Depth Information
Thin-section criteria
Stratigraphic range
Corallinaceans
Fine network structure; cell size < 5 to 15 m; differentiation according to cell size and
Early Cretaceous to
arrangement; caseshaped cavities in lines or isolated within the tissue; crusts, nodules,
recent, possibly already
branches; in transmitted light dark. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pl. 54
Early Paleozoic
Peyssoneliaceans
Network structure; cell size 20 30 m; basal calcification with botryoids; distinctly set
Early Cretaceous to recent
sheets; blades, nodules; in transmitted light golden, yellowish, gray
. . . . . . . . . .Pl. 64/10
possibly also Late Paleozoic
Solenoporaceans
Closely packed vertical filaments, sometimes with horizontal partitions; cell size
Cambrian to Tertiary
10 100 m; no cell differentiation, no caseshaped cavities; nodular and branched . .Pl. 55
(Miocene)
Ancestral red algae (Archaeolithophyllaceans)
Network structure; cell size approx. 10 30 m; cell differentiation; blades and nodules;
Carboniferous and Permian
in transmitted light yellowish, gray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pl. 56/2, 8
(Viséan to Late Permian)
Problematic algae
Ungdarellaceans
Network structure; cell size about 20 m; cell differentiation;very small encrusting or
Carboniferous and Permian
isolated structures; in transmitted light often golden, yellowish
. . Pl. 56/57, Pl. 108/78
Common: Viséan-Moscovian
Stacheinaceans
Indistinct network; very small encrusting structures; in transmitted light often golden,
Carboniferous (Viséan to
yellowish
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pl. 108/10
Moscovian)
Fig. 10.6. General thin-section criteria of some common calcareous red algae.
segment and composed of partitioned filaments, and
peripheral cellular filaments (cortex) surrounding the
medulla (Fig. 10.7G; Pl. 64/11).
At present, the morphology and taxonomy of coral-
line genera are under revision. The identification of spe-
cies should be reserved for specialists. Both, traditional
morphological criteria and neontological features are
used in determining coralline taxa. Identification keys
have been published by Braga et al. (1993) and Rasser
and Piller (1999). Commonly used features for identi-
fying fossil genera are growth form, development of
cells within different parts of the thallus, and repro-
ductive organs.
Morphology: The thallus consists of adjacent calci-
fied filaments. Consecutive cells within core filaments
are connected by primary pit connections or by cell
fusions. The calcified cellular tissue is characterized
by definite arrangements, shapes and sizes of cells. Cells
are very small (5-20 m).
Fig. 10.7. Internal morphology of calcified cor-
alline algae . Both encrusting and erect articulated
corallines exhibit differentiation of the plant tis-
sue into a basal (central) and a peripheral (upper)
part differing in the geometry, arrangement and
size of the filaments. A : Lithothamnion crust over-
growing an older algal nodule. B to E : Basic types
of hypothallus (H) and perithallus (P) organiza-
tion in encrusting corallines. F : Typical growth
form of erect, articulated corallines ( Corallina ).
G : Internal organization of the calcified segments.
A: After Fott (1971), B-G: After Wray (1977).
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