Geology Reference
In-Depth Information
Distribution:
Cambrian to Silurian, possibly also De-
vonian
.
Nuia
is an important rock builder in Late Cam-
brian and Early Ordovician carbonate mounds.
Interpretation:
The fossil has been interpreted as
codiacean alga, but is now regarded as bacterial or
cyanobacterial growth form.
low-water mounds in subtropical to temperate paleo-
latitudes on platforms and in platform-margin areas
around the northern margin of Pangea. Some of the reefs
are reservoir rocks (e.g. Barents Sea; Stemmerick and
Larsen 1993; Ehrenberg et al. 1986). The genus is of-
ten associated with phylloid algae.
Interpretation:
The fossil has been attributed to alga,
hydrozoans, and sponges. Most authors prefer an algal
interpretation, but a sponge interpretation should be
considered as well.
Palaeoaplysina
Krotow 1888 (Pl. 98/7)
Morphology:
The genus is characterized by calcar-
eous, originally aragonitic broad tabular plates that
appear, wavy in cross sections, with external protuber-
ances and an internal cellular fabric with branched
tubes. Length usually 3-10 cm, thickness 0.5-7.0 mm.
The plates often occur as parallel layered accumula-
tions.
Distribution:
Late Carboniferous to Early Permian
(Moscovian to Artinskian).
Palaeoaplysina
built shal-
Thaumatoporella
Raineri 1924 (Pl. 99/2)
Morphology:
The genus is characterized by small
cells arranged in chains forming closed or open irregu-
larly shaped structures, sometimes constructing bridges
between sessile organisms, e.g. corals. Some thaumato-
porellids exhibit only one chamber, others form sev-
Plate 99 Mesozoic Microproblematica
Microproblematica are common in thin sections of Mesozoic limestones and known from shallow-marine and
deep-marine carbonates (-> 1, 10). Many taxa are benthic, others planktonic (-> 1, 10). Encrusting microprob-
lematica are particularly abundant in reef carbonates, occurring both, at the reef surface between and upon reef-
builders (-> 4, 5) or in small cryptic habitats of reef cavities (-> 8, 9). The plate shows thin sections of microfos-
sils, whose systematic position is still under discussion, with exception of the calcispheres (-> 10).
1
Globochaete
Lombard. These spherical hollow calcitic bodies occur as aggregates or in clusters. They are interpreted as
planktonic green algae. The arrows point to a typical serial arrangement. Middle Jurassic (Klauskalk): Grimming, Austria.
2
Thaumatoporella
Raineri, characterized by fine cells (black arrow) arranged in chains or enclosing chamber-like struc-
tures. White arrows point to globular inner structures.
Thaumatoporella
is now enclosed within a separate green algal
group. Early Jurassic (Pantokrator Limestone): Korfu Island, Greece.
3
Microtubus communis
Flügel. These small open tubes commonly occur in aggregates, often embedded within micritic
crusts developed on reef builders.
Microtubus
is a marker fossil indicating the central parts of Norian and Rhaetian reefs.
Late Triassic (Oberrhätkalk, Rhaetian): Feichtenstein, Salzburg, Austria.
4
Bacinella
. The fossil is characterized by an assemblage of variously formed cells that are sometimes arranged in rows.
Bacinella
is common in Mesozoic reefs. Late Triassic (Norian): Jabal Kawr, Oman.
5
Lithocodium
, encrusting a shell fragment (SF). The peripheral structures indicated by the arrow are considered as 'pores'
or 'cortical filaments' depending on the systematic assignment (foraminifera or udoteacean algae).
Lithocodium
is now
regarded as a foraminiferal consortium. It is often associated with
Bacinella
(see Pl. 134/2) and occurs in Triassic,
Jurassic and Cretaceous reefs. Late Jurassic (Kimmeridgian): Ota, west-central Portugal.
6
Tubiphytes
surrounded by a similar but more open network structure called
Plexoramea.
These fossils are abundant in
Middle Triassic and Carnian reef limestones. Middle Triassic (Wettersteinkalk, Ladinian): Blumautal, Germany.
7
Tubiphytes morronensis
Crescenti. This species, associated with
Terebella
(see Pl. 92/10), is abundant in Late Jurassic
and Early Cretaceous platform and slope deposits and in limestones with siliceous sponges. The arrow points to a mili-
olid foraminifera commonly found in the center of the fossil. The
Tubiphytes
network is interpreted as part of the fora-
miniferal wall. Late Jurassic (Treuchtlinger Kalk, Kimmeridgian): Southern Franconian Alb, Germany.
8
Baccanella floriformis
Pantic. These microfossils (arrow) are common in cryptic cavities of Triassic reefs. They repre-
sent most probably bacterially induced carbonate precipitates. Late Triassic (Dachsteinriffkalk, Norian): Gosaukamm,
Austria.
9
Radiomura cautica
Senowbari-Daryan and Schäfer. The fossil is found commonly attached to frame builders or within
micritic cryptic habitats of Triassic and Jurassic reefs. Late Triassic (Oberrhätkalk): Feichtenstein, Salzburg, Austria.
10 Some fossils formerly considered to be microproblematica are no longer problematic with regard to their position. An
example are 'calcispheres'. The thin section shows
Stomiosphaera sphaerica
(Kaufmann) characterized by spheres, 10-
100
m in diameter, with calcitic and organic walls. SEM studies reveal strong morphological differentiation of the wall
supporting an interpretation as calcareous dinoflagellate cysts (Sect. 10.2.1.9). Late Cretaceous (Turonian, Seewen lime-
stone): Seewen, Switzerland.
-> 8: Gaetani and Gorza 1989
