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7 Biostratigraphy of Bryozoa in the ENCI
quarry
This is a re-edited version of an essay by R. Lagaaij,
1951: "Een onderzoek naar de qualitatieve en quantitatieve verspreiding
van de Bryozoa in het Maastrichts tufkrijt, met bijzondere in acht
neming van de Cheilostomata". Mr. Lagaaij did rather extensive research
about the biostratigraphy in the ENCI quarry. Of course the stratigraphy
then used in now old fashioned. Also many of the names of the Bryozoa
are changed due to more recent research. The main purpose of the
research was to test the hypotheses (Umbgrove, 1926) that the Maastrichtian
in the ENCI quarry reflects a constantly shallowing sea. The results
of the research are shown here. The research of R. Lagaaij was not
reinterpreted.
The research done by R. Lagaaij was re-edited to
correct for the recent stratigraphy and can be useful in today's
biostratigraphic research. It can be interesting to reinterpret
the data with the knowledge about sequence stratigraphy. The identification
of the species were not done over again, but relied on the original
research. For actual names of the Bryozoa, see the Alphabetical
Species and synonym list. The original samples are still in
the Naturalis Museum in Leiden.
Further research is needed to set up a good detailed
Bryozoa biostratigraphy in the Maastricht area. The research of
R. Lagaaij can probably also be used for that purpose.
The Research
1500 Cheilostomate Bryozoa were counted and sorted
from 10 Bryozoan layers in the upper part of the Mc section and
the Md1 to Md4 sections in the then used stratigraphy (now Mc is
Nekum member IVe, Md is Meerssen member IVf). The most numerous
Bryozoan genera and other then were plotted in the stratigraphic
column (see Fig. 1). Also the species and their systematic were
shown and their ranges in the stratigraphy (see Fig. 2). Those species
were: Malacostegina
(suborder), Vincularia (genus), other Microporidae (family), Pseudostega
(genus), Beisselina (genus), other Ascophorina
(suborder), Cyclostomatida
(order) and Lepidorbitoides (foraminifer).
Here is the original summary of the research by R.
Lagaaij:
The opinion expressed by Umbgrove (1926, p.268),
as regards the constant shallowing of the Maastrichtian Sea until
coralreefconditions prevailed in the upper part of the profile (MD),
may be generally exact, but needs a slight correction, when details
are considered. From the quantitative analysis of the Polyzoa (Bryozoa)
occurring in the Md-profil, it becomes clear, that the above mentioned
tendency was probably slightly interfered during Md2-Md3 sedimentation.
During Md4-deposition however, similar faciesconditions as dominated
Mc-Md1 sedimentation were restored.
Fig. 1. Original Diagram I from R. Lagaaij. Interpretation recent
stratigraphy marked on the left.
Fig. 2. Original Table II from R. Lagaaij.
© 1999
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