During part of 1991, while
a graduate student at the University of Texas at Austin Institute For Geophysics
(UTIG), I interned at Exxon Production Research Company (EPR) in Houston.
I spent most of my time in a team of explorationists at Exxon International,
working on a regiojnal frontier project assessing the hydrocarbon potential
of the Carpathian Fold and Thrust Belt in Czechoslovakia and Poland.
An eastward extension of the Alps, the Carpathian Orogen
runs northeast between the Czech Republic and Slovakia (the "Beskydy Mountains",
turns due east along the border between Poland and Slovakia (the "Tatra Mountains"),
then curves in a giant arc through western Ukraine into Romania (the "Carpathian
The "Pravcicka" Arch
To the north (outboard) of the fold and thrust belt lies
the West European Plate; itself a mess of crystalline basement, an old northeast-dipping
Variscan subduction zone, a small Lower Paleozoic basin southwest of Prague
(the Barrandien Basin), and a thin Cretaceous cover
of shallow marine and fluvial sandstones in the northern part of
the Czech Republic (the "Czech answer" to Arches National Park). To
the south of the fold and thrust belt, atop the Apulian Plate, lies the Pannonian
Trilobite from the "Barrandien"
The fold and thrust belt consists
of several nappes of varying ages, each with its own distinct lithologic
character. These nappes are the remains of the Tethys Ocean that once existed
between the Asian and Europeans Plates.
The Tethys opened gradually during a Jurassic period of
rifting. In the early stages of the Tethyan opening an important formation
of organic-rich calcareous mud (the Mikulov Marl) was deposited on the floor
of the Tethys. It is believed my most geoscientists that it is this formations
that serves as the source of hydrocarbons for all the fields in the Vienna
Basin and production elsewhere along the fold and thrust belt.
Carpathian Fold and Thrust
Belt (From Picha, 1996)
(Click to see a larger picture)
Grand-Canyon-size canyons were
cut into the edge of the European Plate (e.g. the Nesvacilka Graben) and
probably served as conduits that funneled submarine fans onto the abyssal
plain of the Tethys.
In the Early Tertiary, when the
Tethys began to contract, deep-water turbidites (Sub-Silesian and Silesian
nappes) were thrust over the margin, followed by older and older units (e.g.
Triassic limestones of the Pieniny Klippen Belt), until the final stages
of the shortening when the crystalline Inner Carpathian nappe was plastered
onto the inside of the fold and thrust belt.
Meanwhile, in the Miocene, a curious thing happened along
the outer edge of the fold and thrust belt, in the area where Vienna and
Bratislava lie today. A pull-apart basin opened on top of the still-advancing
nappes: the Vienna Basin. Because of the extremely arcuate nature of the
fold and thrust belt, this area was briefly subjected to transtension and
the Vienna Basin was formed.
Satellite image of the
Vienna Basin located between the eastern end of the Alps (left side) and
the Neusiedler See. Notice the Danube River and the cities of Vienna and
Bratislava (bright spots). Image taken from ESA 1993, Courtesy The Univ.
(Click to see a larger picture)
As it subsided, the Vienna Basin
was filled by Miocene and Pliocene turbidites, deltas, shoreline and fluvian
deposits. These rocks are generally similar in age and depositional setting
to those deposits that filled the narrow foredeep basing outboard of the
of geomorphology, the Carpathian fold and thrust belt is an area of stunning
natural beauty. Each one of the nappes composing the fold and thrust belt,
has somewhat different lithology, and therefore forms its own distinct landscape.
Each one of the nappes composing the fold and thrust belt, has somewhat
different lithology, and therefore forms its own distinct landscape. The
Vienna Basin, lying on top of the Sub-Silesian and Magura nappes, is a flat,
low-lying plain covered with corn fields and orchards.
To the northwest the outcropping Sub-Silesian nappe gives rise to low
limestone hills (The "Palava" Highlands) dotted with vineyards producing
a nice variety of delicious semi-dry red
wines. To the northeast, the Silesian and Magura nappes form rounded
hills, characteristic for landscape underlain by turbidite and other interbedded
clastic rocks. In stark contrast to the wooded wills of the Magura and Silesian
nappes are the jagged white limestone cliffs formed by the Pieniny
Klippen Belt nappe.
Eastern Carpathians in
Deep narrow valleys, swift wild rivers, ancient castles
and chateâux provide a backdrop fit for a romantic painting
(say by Eugène Delacroix).
The "Pieniny" National
In even more contrast, to the east lie the Tatra Mountains, jagged
nine-thousand-foot peaks rising majestically to the sky. The Tatras provide
hiking and skiing comparable only to the Alps and the Colorado Rockies.
Although nearly not as high as many of the mountain ranges in Colorado, the
Tatras convey a much more rugged and austere "mountainous" feel (due mostly
to the fact that this ares is much farther north than Colorado).
The "Spis" Castle
View from the "Ostrva"
Peak of the tarn "Popradske Pleso" and the valley "Mengusovska Dolina"
The results of my summer internship project remain proprietary and cannot
be published without Exxon's consent.
However, AAPG Bulletin
published in 1996 a very comprehensive paper by Frank
Picha, a senior geoscientist with Chevron Overseas Petroleum Inc. (The
paper is based on his 1991 talk at the AAPG International Conference in London
where it won the AAPG International Best Paper Award.) My results were very
similar to this work.
J. Picha, 1996, Exploring for Hydrocarbons Under Thrust Belts: A Challenging
New Frontier in the Carpathians and Elsewhere, AAPG Bulletin, v.80,
No.10 (October 1996), p.1547-1564.