Geology Reference
In-Depth Information
tions, or because they prefer habitats within algal and
sea grass meadows. Depth distribution of endosym-
biotic foraminifera depends on the type of endosym-
bionts. Foraminifera with green or red symbionts are
restricted to shallower depths than those with diatoms
that can occupy greater depths.
Near-coastal, lagoonal, and inner and outer shelf
environments as well as upper and lower slope and ba-
sinal environments differ in foraminiferal association
patterns. Shallow nearshore and lagoonal environments,
down to about 50 m, are characterized by porcelaneous
miliolid foraminifera. Planktonic foraminifera are ab-
sent or rare in shallow-marine environments. Hyaline
rotaliinids occur in shallow and deeper waters. Agglu-
tinated tests are ubiquitous but common on the slope
and also occur at depths of several thousand meters. In
outer shelf environments (about 50 to 200 m) the fau-
nas are dominated by perforate rotaliinid species.
Bathyal depths tend to be dominated by biserial and
triserial agglutinated foraminifers along with some hya-
line rotaliinids and porcelaneous miliolinids.
(B) Planktonic foraminifera are adapted to different oce-
anic layers with particular temperatures and densities.
Temperature-controlled planktonic species exhibit spe-
cific morphological characteristics (shape, size and coil-
ing direction). These adaptions are used together with
geochemical and isotope data as proxies for paleoceano-
graphic interpretations of Cretaceous and Cenozoic pe-
lagic carbonates. Most planktonic foraminifera are re-
stricted to marine salinities of 30-40‰ and live in de-
fined parts of the water column. The majority occurs in
the upper part of the water column within the upper 50
to 100 m near the surface (photic zone). Below 200 m
they are virtually absent. The thin-walled spherical,
symbiont-bearing globigerinids prefer the surface wa-
ters where there is light, while those with thicker walls
and keeled shells (lacking photosymbiosis) tend to be
Fig. 10.23. Different sections through foraminiferal tests of different shapes . A. Single chambered: 1 - axial section,
2 -longitudinal, 3 - tangential, 4 -transversal, 5 - oblique. B . Multichambered uniserial: 1 - axial, 2 - longitudinal, 3 - transversal,
4 - oblique passing through two chambers. C. Multichambered biserial: 1 - axial sagittal, 2 - axial frontal, 3 - longitudinal,
4 - axial oblique, 5 - transversal, 6 - transversal oblique. D. Multichambered planspiral (a, lateral view; b, peripheral view):
1 - axial, 2 - transversal equatorial. E. Multichambered triserial (a, lateral view; b, oral view): 1 - axial, 2 - longitudinal
passing through two chambers, 3 - longitudinal passing through one chamber, 4 - transversal. F. Multichambered trochospiral:
1 - axial, 2 - transversal dorsal, 3 - transversal, passing through an embryonal chamber, 4 - transversal ventral. After Neumann
(1967).
Search WWH ::




Custom Search