Geology Reference
In-Depth Information
ifera, hydrozoans or sponges. Two groups of these mi-
crofossils are common in Late Paleozoic shallow-ma-
rine carbonates and used in the stratigraphic and envi-
ronmental subdivision of platforms and ramps (Fig.
10.9; Box 10.2).
Box 10.2.
Late Paleozoic ancestral red algae
common
in reef limestones, and possible red algae, abundant in
platforms and ramps. Although the systematics of the
latter are controversial and need substantiation, the fos-
sils have a high potential in microfacies analyses. Spe-
cific associations of these algae and of foraminifera al-
low a detailed biozonation and correlation of Carbonif-
erous shelf carbonates (Armstrong and Mamet 1977,
Mamet et al. 1987).
Basics: Ancestral corallines and problematic red algae
Armstrong, A.K., Mamet, B. (1977): Carboniferous microfa-
cies, microfossils and corals, Lisburne Group, Arctic Alaska.
- Geological Survery Professional Paper,
849
, 144 pp.
Johnson, J.H. (1956):
Archaeolithophyllum
, a new genus of
Paleozoic coralline algae. - Journal of Paleontology,
30
,
53-55
Mamet, B., Roux, A., Nassichuk, W. (1987): Algues carboni-
fères et permiennes de l'Arctique canadien. - Geological
Survey of Canada, Bulletin,
342
, 1-143
Wray, J.L. (1964):
Archaeolithophyllum
, an abundant calcar-
eous algae in limestones of the Landsing Group (Pennsyl-
vanian), southeastern Kansas. - Kansas Geological Sur-
vey Bulletin,
170
, 13 pp.
Further reading
: K129
Archaeolithophyllacean red algae
Central hypothallus coaxial, consisting of large po-
lygonal and rectangular cells. Perithallus poorly devel-
oped, cells much smaller. Large conceptacles at the pe-
riphery, commonly exhibiting a yellowish color in trans-
mitted light. Often strongly recrystallized. Common taxa:
Archaeolithophyllum
(Pl. 56/1, 2, 8).
Viséan to Late Permian. Cosmopolitan. Abundant in
Pennsylvanian and Early Permian reefs (reef mounds and
mud mounds).
Ungdarellacean red algae
Millimeter-sized elongated and often ramified en-
crusting nodules, exhibiting rectangular and subquad-
ratic cells that are sometimes differentiated according to
size and arrangement. Skeletal elements hyaline, often
with a golden or yellowish tint in transmitted light. Com-
mon taxa:
Ungdarella
(Pl. 56/7, Pl. 108/7, 8),
Komia
(Pl. 56/6).
Early Carboniferous to Permian. Cosmopolitan.
Abundant in Late Viséan to Moscovian shelf carbonates.
Stacheinacean and related red algae
Millimeter-sized microfossils encrusting a central
support or a substrate. Characterized by a succession of
arched or subquadratic cells arranged irregularly or in
rows. Skeletal elements hyaline. Commonly yellowish
in transmitted light. Common taxa:
Cuneiphycus,
Efluegelia
(Pl. 56/5),
Epistacheoides
(Pl. 108/9),
Stacheia
(Pl. 108/10),
Stacheoides.
Early Carboniferous to Permian. Common in Viséan
to Moscovian platform and ramp carbonates. Rare in
Early Permian shelf carbonates.
10.2.1.5 Udoteacean Green Algae and
Gymnocodiacean Algae
Most modern benthic
green algae
live in freshwater
environments, about 10% of the species also occur in
marine settings. Ancient green algae are almost exclu-
sively marine fossils.
Benthic calcified green algae
are represented by the
Udoteaceae
and the
Dasycladaceae
. The systematic
position of the extinct
Gymnocodiaceae
(green or red
algae) is still under discussion, but better arguments
are in favor of green algae (Mu 1991; Bucur 1994).
Other algal groups related to or interpreted as benthic
green algae are the Early Paleozoic
receptaculitids
(common in Ordovician and Silurian, ranging to the
Permian) and
cyclocrinitids
(Ordovician and Silurian).
Both groups differ in the size of the globular shape (sev-
eral centimeters) of typical calcareous algae, but re-
semble dasyclad green algae in their internal organiza-
tion. They have a central main axis and radially arranged
tightly packed lateral branches forming hexagonal or
rhombohedral facets on the outer surface (Rietschel
1977; Nitecki et al. 1987; Beadle 1988, 1991).
Some of the fossils included within the informal
group of 'phylloid algae' are most probably udotea-
cean green algae (Sect. 10.2.1.6).
Fossil records of marine
planktonic green algae
are
known from the Volvocales and Chlorococcales (Sect.
10.2.1.9). Calcifying planktonic green algae also con-
tribute to the formation of modern and Tertiary fresh-
water carbonates (Müller and Oti 1981).
10.2.1.4 Ancestral Red Algae and
Problematic Red Algae
Several thin-section fossils, predominantly of Late Pa-
leozoic age, are believed to be ancestors of younger
red algal groups, or are assigned to red algae, more or
less persuasively. Some exhibit thalli composed of a
cellular tissue known from true red algae taxa (e.g.
Archaeolithophyllum
)
.
Other taxa can not be related to
existing red algal groups and are therefore assigned to
separate algal groups (e.g.
Ungdarella
) or have been
excluded from the algae and compared with foramin-
