Geology Reference
In-Depth Information
sand-sized carbonates on platforms and ramps. Many
dasyclad limestones (mostly grainstones and pack-
stones) were formed in open-marine lagoonal or back-
reef environments. Examples are Permian
Mizzia
lime-
stones (Pl. 60/6), Middle Triassic
Diplopora
limestones
(Pl. 61/1), Liassic
Palaeodasycladus
limestones (Pl. 62/
1), Late Jurassic
Clypeina
limestones (Pl. 62/5, 6), and
Early Cretaceous
Salpingoporella
limestones (Pl. 63/
7). Late Paleozoic and Mesozoic dasyclads contributed
to the formation of biogenic mounds (e.g. Late Car-
boniferous
Anthracoporella
mounds, Pl. 59/6; Late Ju-
rassic
Neoteutloporella
biostromes, Pl. 59/3).
Recognition of shallow-marine depositional sites:
Different algal groups prefer different depositional sites.
Fig. 10.17 and Fig. 10.19 give a rough picture of the
environmental distribution of Carboniferous dasyclads
and other algal groups.
Plate 64 Late Cretaceous and Paleocene Calcareous Green and Red Algae
Dasyclad algae suffered a significant decline during the Late Cretaceous. The number of genera per stage de-
creased from about 40 in the Early Cretaceous to less than 20 in the Late Cretaceous. A similar drop is shown by
the number of species from the Cenomanian to the Campanian. Maastrichtian dasyclad assemblages exhibit
slightly higher species numbers (up to 15). Late Cretaceous dasyclad species are of value in establishing com-
posite biozonations (Kuss and Malchus 1989). Early Tertiary dasyclads are valuable time markers. The Early
Cenozoic was a time of high dasyclad species diversity connected with a renewal of the algal associations.
Paleocene and Eocene species numbers (81 and 95 respectively) surpass those of the Early Cretaceous. At the
end of the Eocene more than 90% of the Paleocene-Eocene species had disappeared. The Neogene represents a
marked decline for the dasyclads. 20 species were recorded from the Miocene, 8 from the Pliocene, only one
species appears to have survived in recent assemblages, which contain about 35 species, predominantly of the
group Acetabulariaceae.
1 Dasyclad green alga:
Neomeris (Larvaria)
sp. Tangential/axial longitudinal section. Black arrows point to distinctly
differentiated whorls. White arrows indicate the dasyclad alga
Aciculella
. Paleocene (Thanetian): Mariazell, Styria, Aus-
tria.
2 Dasyclad green alga:
Trinocladus perplexus
Elliott. Longitudinal section. Shallow subtidal open platform. Late Pale-
ocene: Priglitz, Lower Austria.
3 Udoteacean green alga:
Halimeda nana
Pia. Longitudinal section. Note the distinct differentiation of axial medulla (M)
and cortex (C). Arrows point to filaments. Open platform. Paleocene: Priglitz, Lower Austria.
4 Dasyclad green alga:
Cymopolia elongata
(Defrance) Munier-Chalmas. Longitudinal section. Differences in size of the
thalli and number of whorls allow low-energetic, moderate or high-energetic (this figure) environments to be differenti-
ated. Same locality as -> 3.
5
Distichoplax biserialis
(Dietrich). A widely distributed microproblematicum, restricted to Paleocene and Early Eocene
carbonates. E: Echinoid spine. Paleocene (Thanetian): Lupina, Western Carpathians, Slovakia.
6 Dasyclad green alga:
Cymopolia inflataramosa
Segonzac. Oblique cross section. Diagnostic criteria are broadened pri-
mary branches (black arrows) and thin short secondary branches (white arrow). Paleocene (Late Thanetian): Hricovske
Podhradie, Slovakia.
7 Composite crust consisting of red algae (top:
Archaeolithothamnium
, A; below:
Pseudolithothamnium album
, PA) and
sessile foraminifera (
Planorbulina
, P). Deeper subtidal environment. Late Maastrichtian: Hochschwab, Styria, Austria.
8 Dasyclad green alga:
Broeckella belgica
Munier-Chalmas. Cross-section. Diagnostic criteria is the broadening of the
primary branches (arrows). The species is an index fossil (Danian and Early Thanetian). Common in lagoonal and back-
reef sediments. Paleocene (Thanetian): Mooshuben, Styria, Austria.
9 Dasycladalean green alga:
Acicularia
cf.
pavantina
d'Achiarc. Note cross sections of ampullae. Same locality as -> 8.
10 Squamariacean red algae (
Peyssonelia
, P) and coralline red algae (
Amphiroa
, A;
Lithophyllum
, L). Criteria of squamariacean
algae: Encrusting aragonitic thalli consisting of a basal layer (hypothallium, HT) from which vertical or arcuate rows of
cells arise (perithallium, PT). Note the difference in the preservation of aragonitic squamariacean and High-Mg calcite
corallinacean algae. Typical association of high energy shallow-marine environments. Late Maastrichtian: Hochschwab,
Austria.
11 Articulated coralline red alga:
Amphiroa
sp. Longitudinal section. Criteria: Medullary segments (S) consisting of long
cells. Distinctly layered cortical tissue (CT). Same locality as -> 10.
12 Crustose coralline red alga:
Sporolithon
sp. Note the linear arrangement of conceptacles (C). Late Paleocene: Priglitz,
Lower Austria.
-> 1-11: Courtesy of H. Tragelehn (Köln).
