Crimean orogen : a nappe interpretation

12 Pages·1996·2.5 MB·English

by  I V Popadyuk

Crimean orogen:
a nappe interpretation
/. V. S. E.
Popadyuk & Smirnov
Ukrainian State Geological Research Institute,
Mitskevich sq. 8, 290601 Lviv, Ukraine
ABSTRACT autochthonous series. The Taurian nappe is com¬
posed of Hauterivian to Aptian flysch. The Yayla
and Taurian nappes each account for horizontal
Detailed surface geological analyses and a northward transport of supra-crustal rocks over a
review of subsurface and published palaeontologi¬ distance of at least 30-40 km; their root zones,
cal data refute the long held notion that the area of which may be located off-shore, have not yet been
the Crimean Highlands was affected by a major identified. The youngest autochthonous strata
Late Triassic-Early Jurassic orogeny, referred to as which are overridden by these nappes yield a mid¬
the Early Cimmerian orogenic pulse. The Taurian dle Late Albian age. The thrust contact between
flysch, which contains abundant reworked Car¬ the Taurian nappe and the autochthon is sealed by
boniferous to Jurassic rock fragments and which Cenomanian limestones. Therefore, the main
was previously thought to be of Late Triassic to deformation phase of the Crimea, during which the
Early Jurassic age, has been redated on the basis of Yayla and Taurian nappes were emplaced, is dated
Ammonites as Hauterivian to Aptian. Correspon¬ as Late Albian and thus correlates with the Austri¬
dingly, an older-over-younger relationship, typical an phase of the Alpine orogenic cycle.
for nappe tectonics, has been established for the In the northeastern part of the Crimea, subsur¬
Late Jurassic carbonates, the Taurian flysch and the face data give evidence for Eocene and younger
Albian-Aptian autochthonous series which crop compressional reactivation of the frontal parts of
out in the Crimean Highlands. the Yayla nappe, corresponding to the Vladislavov-
The topographic relief of the Crimean High¬ ka nappe which involves Late Jurassic to Paleo¬
lands is upheld by 800-1000 m thick Late Jurassic gene strata. The effect of these Late Alpine
reefal and platform carbonates forming the Yayla deformations on the Crimea Highlands is difficult
nappe. In the southern parts of the area this nappe to evaluate for warn of a Late Cretaceous and
rests on the Taurian nappe and further north on younger stratigraphic record.
Popadyuk, I. V. & Smirnov, S. E., 1996. Crimean orogen: a nappe interpretation. In: Ziegler, P. A. & Horvath, F. (eds).
Peri-Tethys Memoir 2: Structure and Prospects of Alpine Basins and Forelands. Mem. Mus. natn. Hist. nut.. 170: 513-524. Paris ISBN:
2-85653-507-0.
514 I V. POPADYUK & S. E. SMIRNOV: CRIMEA
INTRODUCTION
merian (pre-Tithonian) southward thrusting of the
Late Jurassic carbonates and Late Alpine deforma¬
tion of the eastern parts of the Crimean orogen.
Yu.V. Kazantsev (1982) were the first to revise
The southern most parts of the Crimean the classical model of Muratov (1969) in the sense
Peninsula are occupied by highlands which are of nappe tectonics, however, without considering a
upheld by folded and thrusted, partly reefal Late revision of the age of the Taurian flysch complex.
Jurassic carbonates and Early Cretaceous flysch Although these early efforts were strongly criti¬
series. These northeasterly trending highlands, cized (Archipov et al., 1983a, 1983b; Byzova et
which rise to an elevation of nearly 1500 (highest al., 1983), additional impulses were given to the
peak Roman-Kosh Mtn. 1543 m elevation), have a more mobilistic nappe model by the recognition of
length of some 170 km and are up to 50 km wide. nappes in the Kerch Peninsula located to the east
Geophysical data indicate that the Crimean orogen of the Crimean Highlands (Kazantsev and Beher,
extends off-shore in the direction of the Dobrogea 1987; Kruglov and Tsypko, 1988). This discovery
and the Greater Caucasus as well as to the south encouraged the author of this paper to carry out
into the deeper waters of the Black Sea (Khain, further surface geological studies in the Crimean
1994). Highlands. In this respect the excellent and readily
The Crimean Highlands are one of the best accessible outcrops in the Salgir, Tonas and
studied parts of the Alpine chains of Eastern Sukhoy-Indol valleys were closely studied (Fig. 1).
Europe. Surface geological mapping had already Based on the results of these studies, as well as on
commenced during the second half of the 19th cen¬ a review of publications and available subsurface
tury. By the late 1960's more than 1300 papers had data, a nappe model was developed for the
been published on this area. This voluminous lite¬ Crimean Orogen (Popadyuk and Smirnov, 1991).
rature was synthesized by M.V. Muratov in volume In this paper we discuss the rationale which under¬
VIII of the “Geology of the USSR" (1969). In this lies this model and support our concepts with a
fundamental work the classical model for the evo¬ series of structural cross-sections through the
lution of the Crimean orogen was developed. Crimean Highlands (Fig. 3).
According to this model the geosynclinal stage of
the area terminated with the compressional defor¬
mation of the Taurian flysch group during Late Tri-
assic-Early Jurassic times. This Early Cimmerian
orogenic pulse was supposedly followed by a pro¬ TECTONO-STRATIGRAPHIC UNITS OF
longed period of tectonic quiescence during which THE CRIMEAN HIGHLANDS
Late Jurassic carbonates were deposited on the
eroded Early Cimmerian fold belt. Compressional
deformation of the area resumed only during the
Neogene. The distribution of the major tectono-stra-
In this model the Crimean fold belt was tigraphic units making up the Crimean Highlands,
regarded as an inverted basin in the foreland of the as well as the location of the transects discussed
Alpine chains that lacked the classical nappe tec¬ below, are given in Fig. 2. In essence five tectono-
tonics which characterize the true Alpine orogens. stratigraphic units are recognized. These are, in
Although, with the gradual acceptance of plate tec¬ ascending order, the autochthonous unit which
tonic concepts, this interpretation began to be seri¬ includes Early Cretaceous and Middle Jurassic
ously questioned, Muratov and Tseisler (1982) strata, the allochthonous Taurian flysch group, the
continued to adhere to their model. On the other age of which was for a long time a matter of dis¬
hand, after the publication of the paper by pute, the allochthonous Late Jurassic Yayla unit
S.L. Byzova (1980), Khain (1994) visualizes a and the largely post-tectonic Late Cretaceous to
more complex evolution of the Crimean High¬ Cenozoic unit.which records evidence of Late
lands, involving Early Cimmerian deformation of Alpine deformation.
the Taurian flysch trough, followed by Late Cim¬
Source:
PERI-TETHYS MEMOIR 2: ALPINE BASINS AND FORELANDS 515
34* 35*
FECJDOSIA
SIMFEROPOL
BAKHCISARAY
LUSHTA
,SEVASTOPOL rachinshaya-1 h
(achin5^c)g-2C!lp[
YALTA
FIG. 2. Tectonic sketch-map of Crimean Orogcn.
I: Yayla nappe; 2: Taurian nappe; 3: Early Cretaceous autochthonous series; 4: Late
Cretaceous-Miocenc neo-autochthonous series; 5: Vladislavovka nappe; 6: main
thrust-faults; 7: postulated normal fault; 8: location of cross-sections given in Fig. 3;
9: well locations
Source:
516 I V. POPADYUK & S. E. SMIRNOV: CRIMEA
Autochthonous Unit
regarded as reworked. Their age ranges from Car¬
boniferous to Permian, Middle and Late Triassic to
Early and Middle Jurassic. The shales of the Tauri¬
The structurally lowest unit, which outcrops in an group contain only rare fossils. Conventionally
the northern valleys of the Crimean Highlands, is the Taurian flysch group has been assigned a Late
referred to in our model as the autochthonous unit. Triassic age. The Eski-Odra formation, regarded as
In outcrops it consists of generally weakly forming part of the Taurian Group, was, however,
deformed dark-gray, plastic Albian and Aptian thought to have an Early Jurassic age. By some the
clays, Barremian thin bedded flyschoid sands, silts Taurian flysch was thought to range downwards
and shales, Hauterivian to Valanginian rhythmical¬ into the Middle Triassic (Dagis and Shvanov,
ly bedded calcareous shales, silts and limestones 1965) and the Eski-Odra formation to be as young
and Berriasian calcareous shales and limestones. as Middle Jurassic (Shalimov, 1960).
According to surface geological mapping and the In some areas of the western Crimean High¬
results of boreholes, this sequence attains thick¬ lands, the shales of the Taurian group contain lime¬
nesses of the order of 3.5 to 4.5 km and rests dis- stone blocks and olistostroms which yield early
conformably on a Middle Jurassic continental, and middle Early Jurassic fossils Menner et al.,
coal-bearing series which exceeds 1 km in thick¬ 1947, see pp. 69-70). The occurrence of Early
ness. There is no information on the age. lithology Jurassic faunistic remnants was also noted by
and thickness of the pre-Mid-Jurassic autochtho¬ Muratov (1960), Kazakova (1962) and
nous series and the basement on which it rest. Koronovsky and Mileyev (1974). A.S. Moiseev,
Where control is available, the is no evidence for one of the best experts in Crimean geology,
Late Jurassic carbonates in the autochthonous remarked explicitly that the Late Triassic limestone
series, either due to their non-deposition or due to blocks “represent themselves only blocks within
pre-Cretaceous erosion. the Taurian shales, similar to blocks of Permian
rocks" (see Menner et al., 1947, pp. 58). A similar
view was held by O.G. Tumanskaya who observed
between the Bodrak and Salgir rivers that Permian,
Taurian Flysch Unit
together with Liassic and Triassic limestones,
formed a cliff consisting of blocks of different size
which had settled into Triassic shales containing
The Taurian flysch group, which was already Pseudomonotis caucasica (see Menner et al., 1947,
recognized by Vogdt in 1902 as a special unit pp. 55). On the southern shore of the Crimea, near
(Menner et al., 1947), overlays in outcrops Albian the village of Rybachiye, located to the west of
and older autochthonous strata. The Taurian flysch Sudak, Taurian flysch equivalent strata yielded
consists of intensely deformed dark-coloured, often Bathonian fossils (Lychagin et al., 1956). From the
black, rhythmically and thinly bedded shales, sili- Eski-Odra sequence, considered as having an Early
ciclastic sands and silts. Within this sequence a Jurassic age. Middle Jurassic as well as Permian
coarse-clastic facies, referred to as the Eski-Odra and Triassic fossils were retrieved (Muratov, 1960,
formation, is locally recognized; it consists of 1969; Koronovsky and Mileyev, 1974). According
sandstones, fine to coarse conglomerates and in to Shalimov (1960), the lower levels of the Eski-
some cases even giant limestone blocks which Odra formation (the so-called Salgir unit) contain
yield fossils of Carboniferous, Permian, Triassic Early Jurassic fossils whereas higher levels yield a
and Lower Jurassic age. In some areas the Taurian mixture of Middle Jurassic, Late Triassic, Permian
flysch contains diabase bodies and tuffs. and Carboniferous fossils. However, the most
The Taurian group has yielded numerous fos¬ interesting finds were made by Dekhtyareva et al.
sils such as Ammonites, Brachiopodes, Pelecipods, (1978) who describe from the Eski-Odra formation
Gastropods, Beleminites, Crinoides, Foraminifera near Simferopol, apart from Triassic faunas, the
and plant imprints. As the majority of these fossils occurrence of Ammonites straddling the Hauteriv-
stem from carbonate olistoliths contained in the ian-Barremian and the Middle-Late Aptian bound¬
coarse-clastic Eski-Odra facies, they must be aries.
Source:
PERI-TETHYS MEMOIR 2: ALPINE BASINS AND FORELANDS 517
From the above it is concluded, that all Car¬ Yayla Unit
boniferous to at least Jurassic fossils, which were
retrieved from limestone or sandstone blocks as
well as from sandstones and shales of the Taurian In outcrops, the Yayla unit overlays variably
group, are reworked and therefore cannot be inter¬ the Taurian flysch or different parts of the
preted as giving the depositional age of the Taurian autochthonous unit. The Yayla unit is composed of
flysch. In this respect, even such delicate pelagic Late Jurassic, partly reefal carbonates, which range
shells as Pseudomonotis caucasica Witt were in age from Kimmeridgian to Tithonian, and attain
reworked and are now found in a secondary posi¬ maximum thicknesses of 800-1000 m. Locally a
tion. For example, V. Bodylevsky described basal conglomeratic unit is evident which usually
intensly deformed black shales containing blocks is assigned to the Oxfordian-Early Kimmeridgian.
of calcareous sandstone and quartzite with pur¬ In a few places the Yayla unit appears to include
plish-red nodular siderite from which he retrieved, Neocomian carbonate flysch. The Yayla carbo¬
apart from Pseudomionotis caucasica, also Halo- nates, which uphold the relief of the Crimean
bia and Proarcestes (Late Triassic). In some cases Highlands, are deformed to various degrees,
broken pieces of Pseudomonotis are found in fri¬ though distinctly less intense that the Taurian
able shale intercalations, indicating, according to flysch.
V. Bodylesky, that they were reworked in subma¬
rine flows or by wave action. More rarely
Pseudomonotis occurs in nodular siderite where
Late Cretaceous and Cenozoic Neo-
mainly Halobia is present (see Menner et al.f 1947,
autochthonous Unit
pp. 65). In our opinion this does, however, not nec-
essarely mean that these shells were reworked, as
first assumed by V. Bodylevsky.
On the other hand, it is significant, that Late Along the northern margin of the Crimean
Jurassic carbonate fragments have never been Highlands, Late Cretaceous and Cenozoic strata
reported from the Taurian flysch. Morover, it is unconformably overlay the mildly deformed
interesting to note that the Hauterivian-Aptian autochthonous unit and the more intensely
Ammonites were also found in carbonate frag¬ deformed Taurian and Yayla units. In the northeast¬
ments, suggesting that they were reworked from ern part of the Crimea, Cretaceous and Faleogne
the Yayla allochthon as carbonates of this age are strata, together with Late Jurassic carbonates, are
not known from the Crimean autochthon. involved in the so-called Vladislavovka nappe, a
At present no reliable in-situ fossils have been structure that obviously records Late Alpine reacti¬
identified which could date the Taurian group. vation of the Yayla nappe (Fig. 2).
However, considering the youngest Ammonites,
the Taurian flysch is provisionally assigned a Hau-
terivian to Aptian age.
In view of its intense deformation, the deposi¬
tional thickness of the Taurian flysch cannot be REGIONAL STRUCTURAL
determined. Moreover, no data are available on the CROSS-SECTIONS
direction of clastic transport. On the other hand,
the occurrence of coarse mass flow deposits and of
olistoliths and olistostroms within the Taurian
flysch, composed of Carboniferous to Early Juras¬ In Fig. 3 we present a set of regional structural
sic carbonates, indicates that it was deposited cross-sections through the Crimean Highlands.
under tectonically increasingly unstable conditions These transects are based on detailed surface geo¬
in a deeper water basin of as yet unknown origin. logical mapping and on an integration all available
subsurface data. In the following results of our
studies along the different transects will be dis¬
cussed.
518 I. V. POPADYUK & S. E. SMIRNOV: CRIMEA
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PERI-TETHYS MEMOIR 2: ALPINE BASINS AND FORELANDS 519
Belbek Valley
the eastern slopes of this valley, massive Late
Jurassic limestones, forming the Yayla plateau, rest
directly on Albian clays. The contact between the
The cross-section through the Belbek Valley Jurassic carbonates and the Albian clays is con¬
area is built on surface geological data and the cealed by scree slopes and giant blocks which have
results of wells Kachinskaya-1 and -2 (Fig. 3, pro¬ tumbled down from the edge of Yayla plateau.
file A-B). Kachinskaya-1 was spudded in gently However, as this contact is clearly marked by a
north dipping Cenomanian limestones resting system of springs, it can be readily mapped. The
unconformably on the tightly folded Taurian contact between the Albian clays and the Late
flysch. Upon penetrating the base of the latter, the Jurassic limestones is interpreted as a sub-horizon¬
well entered into Aptian-Albian shales forming tal thrust fault.
part of the autochthonous sequence. After drilling Along the southern and western slopes of the
some 750 m of Early Cretaceous shales, a conti¬ Salgir Valley, the Early Cretaceous sequence
nental, coal-bearing Middle Jurassic sequence was extends stratigraphically downwards into the Apt¬
encountered. The well was terminated before ian and consists of dark-grey clays containing silty
reaching the base of this Middle Jurassic series. and fine-grained sandstone intercalations. In one of
Kachinskaya-2 was spudded in Taurian flysch and the tributaries of the Salgir river the Aptian
entered Albo-Aptian clays at a depth of 920 m; sequence is directly overlain by the Taurian flysch;
after penetrating 1854 m of little deformed Early the latter consists of strongly deformed, rhythmi¬
Cretaceous and 1169 m of Middle Jurassic sedi¬ cally bedded shales, silts and quartzitic sandstones.
ments, the well was abandoned. However, the contact between the Aptian clays and
Based on surface geological data and extrapo¬ the Taurian flysch is poorly exposed. Similarly, the
lation of the well information it appears that the contact between the Taurian flysch and the over¬
thickness of Taurian flysch increases southwards to laying Jurassic carbonates is essentially concealed
about 1.5 km. The Yayla-Ay-Petry mountain is by scree. In this area the Jurassic sequence consists
capped by some 1000 m thick Late Jurassic car¬ of massively bedded Kimmeridgian conglomerates
bonates which rest directly on the Taurian flysch. with a carbonate matrix; these grade upwards into
To the southwest of the Belbek Valley, the Yayla the massif Tithonian carbonates. The components
carbonates cover the entire Taurian flysch and are of the Kimmeridgian conglomerate are made up of
in turn overstepped by Cenomanian deposits quartz, sandstones, metamorphic shales and lime¬
(Fig. 2). stones.
The base of the Yayla and as well as of Tauri¬ Topographically speaking, the Late Jurassic
an allochthon correspond to gently southward dip¬ conglomerates and limestones form the uppermost
ping thrust planes which are sealed by Cenomanian unit. Further south, this unit rests on highly
sediments along the northern margin of the deformed Taurian flysch and further to the north
Crimean Highlands. This indicates that these directly on weakly deformed Aptian and Albian
allochthons were emplaced during the Late Albian clays. Where present, the Taurian flysch overlays
on a little deformed autochthonous sequence, con¬ Early Cretaceous clays and thus forms the middle
sisting of Aptian-Albian shales which rest discon- unit. The Albian-Aptian clays form part of the
formably on a thick Middle Jurassic sequence. basal autochthonous unit. Both the Taurian flysch
and the Late Jurassic Yayla unit are allochthonous
and were apparently thrusted northwards over the
autochthonous Aptian-Albian clays. Across the
Salgir Valley
Salgir Valley, erosion has cut through the Yayla
and Taurian thrust sheets into the underlying
autochthonous unit; as such the Salgir Valley rep¬
In the topographically lowest part of the Salgir resents a tectonic half-window. Surface geological
Valley, dark-grey to black, plastic and weakly evidence indicates the the autochthonous series
deformed Albian clays outcrop in several tribu¬ extend a minimum of 20 km under the combined
taries of the Salgir river (Fig. 3, profile C-D). On Yayla and Taurian thrust sheets. The Bayrakly and
520 I. V. POPADYUK & S. E. SMIRNOV: CRIMEA
Medshyd-Kyr hills are upheld by klippen of the Berriasian age. Since these carbonates rest on
Yayla thrust sheet which are partly underlain by the Albian shales, they are attributed to the Yayla
Taurian thrust sheet. Although the southern part of nappe. Apparently this nappe rests in the Tonas
the cross-section C-D is based on limited subsur¬ Valley directly on various levels of the autochtho¬
face data and is therefore schematic, it suggests nous sequence. The Taurian nappe is only recog¬
that the Yayla thrust-sheet was transported north¬ nized under the southern parts of the Karaby-Yayla
wards over a distance of at least 35 km along a hills from where it continues to the Black Sea
sub-horizontal thrust-fault, separating it from the coast. The Karaby-Yayla hills form part of a major
Taurian thrust-sheet, which in turn traveled a simi¬ Yayla nappe klippe.(Fig. 2). Similar to the Salgir
lar distance over the autochthonous foreland. Both Valley, the Tonas Valley is interpreted as a tectonic
the Yayla and the Taurian thrust-sheets can be half window which developed in response to ero¬
regarded as major north-verging nappes. sion of the allochthonous units. Surface geological
criteria indicate for the Tonas Valley area a mini¬
mum of 15 km northward transport of the Yayla
nappe over the autochthonous foreland.
Tonas Valley
Sukhov-Indol Valley
The Tonas Valley is located in the head-waters
of the Biyuk-Karasu river (Fig. 1). South of the
city of Belogorsk, weakly deformed Aptian-Albian
clays occupy the valley floor (Fig. 3, profile E-F). On the eastern slopes of the Idol Valley,
5.5 km south of Belogorsk, outcrops of thinly bed¬ Mount Agarmysh represents the northernmost rem¬
ded flyschoid dark-gray shales, silts and sand¬ nant of the Yayla nappe (Fig. 3, profile G-H;
stones of Barremian age are observed. Further Fig. 4). Late Jurassic limestones, which uphold this
upstream, progressively older strata are exposed; a mountain, rest directly and in thrust-contact on
more shaly section is followed by monoclinally Albian-Aptian autochthonous clays. As nowhere
north dipping rhythmically bedded calcareous else, it is here possible to closely observe the inter¬
shales, siltstones and limestones of Valanginian- nal structure of the Yayla nappe. Mount Agarmysh
Hauterivian age and Berriasian calacreous shales provides in a cliff-face of over 400 m and in a
and limestones. The lower parts of this sequence quarry on its southern flank excellent exposures.
are characterized by 10-15 m thick cycles, each of These show that the upper parts of Mount
which commences with a limestone conglomerate Agarmysh are composed of gently folded, massif
which grades upwards into limestones and calcare¬ Tithonian limestones (Fig. 4b). Along the southern
ous shale. The basal parts of the Cretaceous are flank of Mount Agarmysh, fine-grained Neocomi-
characterized by 1-2 m thick limestone beds. an siliciclastic flysch and conglomeratic lime¬
Along the road leading up to the Alikot-Bogas stones, intercalated with calcareous shales and
pass, more strongly deformed calcareous shaly reminiscent of the Berriasian series of Tonas Val¬
flysch, containing sand intercalations, is observed; ley, are exposed. In the Agarmysh quarry, an olis-
these sediments are interpreted as equivalents of tostrom is recognized which is composed of large
the Barremian.strata seen south of Belogorsk. Late Jurassic limestone and Neocomian siliciclas¬
In the Tonas Valley a 3.5-4.5 km thick tic flysch blocks; these are encased in a shaly
sequence of Albian to Berriasian flyschoid matrix of unknown age (Fig. 4a). The thrust con¬
autochthonous series can be observed. However, its tact between the Tithonian to Neocomian sedi¬
base has not been seen and it is unknown what ments of the Yayla nappe and the underlaying
underlies it. Apto-Albian shales is sub-horizontal and appears
Four kilometres to the south of Belogorsk, the to be paralleled by a subsidiary thrust fault located
hills flanking the Tonas Valley are capped by some 110 m above the sole-thrust of the Yayla
massively bedded Late Jurassic limestones and nappe.
alternating limestones and shales of Tithonian-
Source: MNHN. Paris
PERI-TETHYS MEMOIR 2: ALPINE BASINS AND FORELANDS 521
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522 I V. POPADYUK & S. E. SMIRNOV: CRIMEA
The northern part of section G-H is based on instance, in the Alma and Bodrak valleys. At some
sub-surface data which indicated that the sole- stage the question of the lower age limit of the neo-
thrust of the Yayla nappe plunges northwards and autochthonous series gave rise to considerable
that it was apparently active during Cenozoic times controversy. However, in view of a definitely Mid-
as evident be the imbrication of Late Cretaceous Albian upper age limit of the autochthonous series,
and Paleogene sediments. A similar pattern is we conclude that the final emplacement of the
shown in profiles I-J and K-L which cross the Yayla and Taurian nappes occurred during the Late
Vladislavovka nappe and are closely controlled by Albian.
boreholes. Several wells drilled in this area pe¬ Therefore, the main deformation phase of the
netrated the basal sole-thrust and bottomed below Crimean Highlands can be safely dated as Late
Late Jurassic carbonates in little deformed Neoco- Albian. As such it coincides with the Austrian
mian sediments (Voloshyna, 1977). phase of the Alpine orogenic cycle and not, as pre¬
The southern parts of profile G-H illustrate viously postulated, with the Early Cimmerian
that the Taurian nappe appears beneath the Yayla phase (Muratov, 1960, 1969; Muratov and Tseisler,
nappe to the south of an erosional window in 1982). Similarly, a Mid-Cretaceous compressional
which Neocomian flyschoid series of the phase governed the development of the Dobrogean
autochthon are exposed. On the basis of this pro¬ orogen for which a previously postulated Early-
file, a horizontal northward transport of the Yayla Cimmerian compressional deformation must be
nappe, amounting to some 35 km, can be postu¬ rejected on the basis of newer litho- and biostra-
lated. tigraphic data (Gradinaru, 1984).
For the northeastern part of the Crimean High¬
lands, subsurface data clearly demonstrate an
Eocene and younger reactivation of the Yayla
nappe; this reactivated zone is referred to as the
DISCUSSION Vladislavovka nappe. The extent to which the
remainder of the Crimean Highlands were affected
by these Cenozoic deformations is uncertain. How¬
ever, the erosional edge of the Cenomanian and
Based on the results of our research, we pro¬ younger post-Austrian neo-autochthonous series
pose that the configuration of the Crimean orogen suggest at best a regional upwarping of the entire
is dominated by the Yayla nappe, which involves area and minor faulting. Such upwarping of the
mainly Late Jurassic carbonates, and by the Tauri¬ entire Crimean Highland probably entailed a modi¬
an nappe, which is composed of Early Cretaceous fication of the geometry of the Yayla and Taurian
flysch. Palaeontological, surface geological and nappe sole-thrusts.
sub-surface data clearly demonstrate that emplace¬ The Yayla nappe, which at present consists of
ment of both nappes resulted in the superposition a system of klippes, is presumably rooted off-shore
of older over younger strata. in the Black Sea. Remnants of this major nappe,
The Yayla and the subjacent Taurian nappe which attains thickness of some 800 to 1000 m,
were thrusted northward over an autochthonous indicate that is was transported in a northwesterly
series which includes Middle Albian.and older direction over a distance of at least 40 km; its later¬
strata. At their northern margin, both the Yayla and al extent is about 140 km. Although the internal
the Taurian nappes are overstepped by undeformed structuration of the Yayla nappe is very complex
Cenomanian and younger sediments which also and is far from being resolved, its sole-thrust is
seal their basal thrust-faults. Within the basal parts sub-horizontal and plunges only northwards in the
of these post-tectonic transgressive sediments, domain of the Vladislavovka nappe.
reworked Hauterivian, Barremian, Aptian and In a strike direction the Taurian nappe extends
Albian faunas were recognized, together w-ith lime¬ over a distance of 140 to 150 km. In a dip direction
stone conglomerates and fragments of Taurian its distribution is very variable; in the Yalta-
flysch; these basal beds grade upwards into undis- Bakhcisaray sector it has a length of at least 40 km
putable Cenomanian limestones as seen, for whereas in the Alushta-Sudak sector and to the
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