German and International Research on Oman 1998
The Hawasina Nappes of the Oman Mountains: geological significance for science and economy =
Geologie in Wissenschaft und Wirtschaft: Bedeutung der Hawasina-Decken der Oman-Berge
by Dr. Oliver Weidlich and Dr. Michaela Bernecker [abstract]
The main interest of geologists during the investigation of the Oman Mountains
has been concentrated on the Semail Ophiolite, which is interpreted as a 90
million years old oceanic crust sheet from Cretaceous times. Currently, the
Hawasina Nappes, which are regarded as a relic of a sedimentary basin situated
formerly north of the Arabian platform, become increasingly interesting for various
geologists.
Since 1990 our studies are focused on calcareous blocks of the Hawasina
Nappes, which record a timeslice of earth history during the Permian and Triassic
(285-225 million years ago). The blocks represent - comparable to modern
environments in the Caribbean or the Red Sea - reefs and lagoons with a variety of
organisms being significant for both working in industry and university.
Scientific significance: the reefal blocks and their fossil remains are important
recorders of Permian and Triassic times. One aspect of our research is conducted
to the description and quantitative analysis of the fossils. In contrast to other
contemporaneous localities in Austria or Italy paleontological data are rare from
the Oman Mountains and an important cornerstone for comparisons. After the
description of the taxonomic inventory, the next step is an interpretation of the
paleoenvironment based on fossils. Significant variations in the biotic composition
record regional control mechanisms as well as dramatic global changes at the
Permian-Triassic boundary, which is a global extinction event. Regional control
mechanisms caused unique faunas like Permian coral reefs or distinct Triassic
coral communities.
Economic significance: Beyond these academic aspects, fossiliferous reef
limestones are highly attractive building stones. Further economic significance as
fillers, e.g. in high quality paper, plastic, paints and medicine, resulted from
extraordinary high carbonate productivity due to rapid growth of reefbuilders
outpassing clastic impurities. This economic importance may be limited either by
terrigenious input or by alteration processes of the carbonate in the subsurface
(diagenesis). Dolomite, quartz and clay minerals reduced the carbonate content of
the investigated material to a varying degree. Using a combination of staining
techniques of carbonates, digital image analysis, and image arithmetics we
quantify the above-mentioned phenomena on different scales (km-sized blocks to
mm-sized pores) and assess the economic importance of various limestones:
(1) Reefal carbonates of Permian age are commonly of limited importance due to
plastic impurities, dolomitization, and silicification.
(2) Platform limestones of Permian and Triassic age are dolomitized to a varying
degree and of heterogenous quality.
(3) By contrast, Triassic reef limestones are of economic interest due to high
carbonate contents.
In connection with a group of students envolved in our research project, our
preliminary data will be completed by detailed geological mapping of specific
areas.
Index of Papers presented at the Oman Conference 1998
Oman Conference 1998 - Main Page
Oman Studies Centre - Main Page
Last updated on 10 June 1998.