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Palaeoecologically significant wood genus Xenoxylon discovered in the East Stara Planina Mts. (East Bulgaria) Balaban Formation (Toarcian, Early Jurassic)

Authors:
Marc Philippe at Claude Bernard University Lyon 1
Marc Philippe
Platon Tchoumatchenco at Geological Institute BAS
Platon Tchoumatchenco
  • Geological Institute BAS
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In the Toarcian (Lower Jurassic) Tethyan rocks of the Mator Basin wood fragments were discovered for the first time in Bulgaria. They were determined as Xenoxylon phyllocladoides Gothan, a biomarker for a cold and/or humid palaeoclimate.
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Доклади на Българската академия на науките
Comptes rendus de l’Acad´emie bulgare des Sciences
Tome 61, No 5, 2008
GEOLOGIE
Stratigraphie et volcanologie
PALAEOECOLOGICALLY SIGNIFICANT WOOD GENUS
XENOXYLON DISCOVERED IN THE EAST STARA
PLANINA MTS. (EAST BULGARIA) BALABAN
FORMATION (TOARCIAN, EARLY JURASSIC)
Marc Philippe, Platon Tchoumatchenco∗
(Submitted by Academician T. Nikolov on February 22, 2008)
Abstract
In the Toarcian (Lower Jurassic) Tethyan rocks of the Mator Basin wood
fragments were discovered for the first time in Bulgaria. They were determined
as Xenoxylon phyllocladoides Gothan, a biomarker for a cold and/or humid
palaeoclimate.
Key words: Tethyan Lower Jurassic, Balaban Formation, East Stara
planina Mts., Xenoxylon, palaeoclimate
Introduction. Triassic and Jurassic Tethyan basin type sediments take part
in the structure of Eastern Stara Planina Mts. (East Bulgaria) [1, 2]. They have
been sedimented in an east-west primary oriented basin – Mator Basin, situ-
ated south of the contemporaneous exposures of these rocks. Later these rocks
were thrusted northward and took part to the composition of large nappe struc-
tures. These tectonically allochtonous Triassic-Jurassic siliciclastic rocks in East-
ern Stara Planina Mts. are subdivided upwards into the trilogy of Sinivir – flysch
alternation (Middle Norian-Early Toarcian), Balaban – sandstones (Toarcian?)
and Kotel Formations – black shales (Middle Jurassic). To the south the Mator
Basin was limited by a shelf on which an uplifted area existed – the Zlatarski
Exotic Range. Probably in the piedmont of it grew the forest wood Xenoxylon
phyllocladoides, described in the present paper. The fragments of this fossil wood
had been transported into the basin and sedimented together with the sandstones
of the Balaban Formation (Plate II, figs. 1, 2).
The aim of this paper is the documentation of the first find in Bulgaria of the
important wood species Xenoxylon phyllocladoides Gothan. P. Tchoumatchenco
The field researches in Bulgaria were made under the Project NZ 1310/03 of the National
Science Fund of the Bulgarian Ministry of Education and Science.
633
Fig. 1. Lithological log of the Balaban Formation – Toar-
cian (Lower Jurassic), Balaban River valley, south of Do-
bromir Village, Burgas district
made the field study and col-
lected the palaeontological ma-
terial; M. Philippe executed
the laboratory researches and
the palaeontological determi-
nation and description of the
studied species.
Systematic palaeonto-
logy:
Morphogenus Xenoxylon
Gothan, 1906
Types-species: Xenoxylon
latiporosum (Cramer) Gothan
(Pinites latiporosus Cramer)
(vide Philippe &Cantrill)
[3].
Xenoxylon phyllocladoides
Gothan, 1906
(Plate I, figs A–D)
1906. Xenoxylon phyllo-
cladoides Gothan [4], Verh.
Russ.-Kais. Mineral. Gesell. 44:
454, text-fig. 4.
Note. The species was
first described by Gothan [4],
but the protologue included
only a sketch of the tracheid
radial wall pitting as an il-
lustration. We have not been
able to locate the type mate-
rial yet, despite long researches
in Poland with the help of
Michal Zaton. Near Czen-
toschaw (Southern Poland),
however, we found several
topotypes which we illustrated
(Philippe et al., [5], Fig. 4
C & D).
Material. Samples No
MP 1266, MP 1267, to the
south of the Village of Do-
bromir, Balaban Dere River,
634 M. Philippe, P. Tchoumatchenco
Burgas district, East Bulgaria. Studied with SEM and Parlodion casts (see
Philippe [6] for the methods). This material was briefly mentioned in Philippe
et al. [5], under the name of Circoporoxylon grandiporosum Schultze-Motel ex
M¨uller-Stoll et Schultze-Motel, but was not described nor discussed. We give here
a full nomenclatural and taxonomical treatment.
Description. A piece of homoxylous secondary xylem, without resin chan-
nels; growth-rings sharply marked, late wood narrow but strongly differentiated;
rays uniseriate, mostly (2) 3 – 7 (11) cells in height; tracheid radial walls with
variable but always uniseriate pitting; areolate pits mostly contiguous and round
(circa 85%, n= 152), sometimes distant and round or rarely contiguous and
strongly flattened (xenoxylean); ray cell walls thin and unpitted, except for cross-
fields which display a large circular oopore occupying the whole field, occasionally
slightly bordered, axial parenchyma not observed.
Determination. Co-occurrence of xenoxylean radial pitting and large win-
dow-like oopores is typical (Philippe and Bramford [7]) for the form-genus
Xenoxylon Gothan. Among Xenoxylon species, a group with mixed type of radial
pitting is clearly distinct (Philippe and Th ´
evenard [8], the so-called “phyllo-
cladoides-group”. Several species have been described within this group, based on
features of discussed value (occurrence of tangential pitting, shape of cross-field,
Sanio’s Rim, etc.). The Bulgarian samples fit well with the Polish topotypes. Thus
we assigned them to Xenoxylon phyllocladoides Gothan.
Taxonomical note. In a first attempt to determine these samples we did
not manage to observe xenoxylean radial pitting, despite that we had observed
more than 60 individual pits. Samples were thus determined as Circoporoxylon
grandiporosum. This species was first described in Schultze-Motel ex M¨uller-Stoll
et Schultze-Motel (‘grandiporosum’) [10]: 65, text-fig. 2a–c, Pl. 1 figs 5–7, Pl. 2
fig. 8. The species was first described in Schultze-Motel’s thesis [9], but this
was not a nomenclaturally valid publication. That name was validly published
much later by M¨
uller-Stoll and Schultze-Motel [10], with a cacography
(“grandiporosum”). It is only recently, while preparing microphotographs of MP
1266, that we eventually came across much flattened radial pits.
The taxa X. phyllocladoides and C. grandiporosum are very similar. Only
the absence of xenoxylean radial pitting distinguishes the former, and as usual
negative features always are delicate to deal with. These two species are com-
monly found associated, for example in Lower Toarcien Posidonien-Schiefer of
Braunschweig area, in Mid-Bajocian Humphresianum zone clays of Osnabruck
area (Northern Germany unpublished data, based on samples kindly sent by
Frank Wittler), or in three levels, dated respectively as Late Pliensbachian, Early
Toarcian and Early Bajocian, of Jameson Land (Eastern Greenland, unpublished
data based on a review of material deposited in Copenhagen Geology Museum).
Despite that we have not yet revised C. grandiporosum type, this could be a
taxonomical synonym of X. phyllocladoides.
Compt. rend. Acad. bulg. Sci., 61, No 5, 2008 635
Distribution. In Europe Xenoxylon phyllocladoides was found in strata
dated from the most earliest Jurassic to Early Cretaceous (Philippe and Th´eve-
nard, [8]). Albeit it was quite commonly found in the Lower and Middle Jurassic,
it was rarely encountered in rocks younger than the Callovian, except in the Arc-
tic. During the Liassic (Table 1), and especially during Spinatum and Serpentinus
zones, it was widespread, with data to as much south as 30◦N (palaeolatitude).
During the beginning of the Aalenian (Opalinum Zone) it still occurred in West-
ern Europe, however, subsequently its south-western limit moved north-eastward
and stretched from Yorkshire to Poland through Northern Germany.
T a b l e 1
Xenoxylon phyllocladoides data for the Liassic of Europe (Data given as “unpublished” are
personal data not yet published)
Stage Locality Source
Toarcian
Rhˆone, France unpublished data
Jameson Land, Greenland unpublished data
Lower Saxony, Germany M¨uller-Stoll & Schultze-
Motel [11], 1988
Domerian (Late Yorkshire, UK Morgans [12], 1999
Pliensbachian Alsace, France unpublished
Franche-Comt´e, France Philippe [6], 1995
Carixian (Early Jameson Land, Greenland unpublished data
Pliensbachian) Lower Saxony, Germany M¨uller-Stoll & Schultze-
Motel [11], 1988
Sinemurian no data
Hettangian W¨urttemberg, Germany M¨uller-Stoll & Schultze-
Motel [11], 1988
Discussion. Fossil wood can be interpreted in palaeoclimatological terms
in various ways. Most commonly unifortarism was used, although it is based on
Plate I
A. Xenoxylon phyllocladoides Gothan. Radial view, mixed type of radial pitting, pits either
round and spaced, round and contiguous or compressed. SEM
B. Xenoxylon phyllocladoides Gothan. Radial view, xenoxylean pitting on the right hand
tracheid. SEM
C. Xenoxylon phyllocladoides Gothan. Radial view, mixed type of radial pitting, some
opposite pairs in the middle part. SEM
D. Xenoxylon phyllocladoides Gothan. Radial view, late wood with one (rarely two) unbor-
dered oopore per cross field and small round spaced radial pits on tracheid walls. SEM →
636 M. Philippe, P. Tchoumatchenco
two strong hypotheses. First the fossil wood is put in relationship with a modern
systematic relative or a modern equivalent. Then the ecological requirements of
this modern taxon are considered to be similar to those of the fossil. This dou-
ble hypothesis strongly limits the interest of uniformitarism, especially for taxa
without close modern relatives, which is the case for Xenoxylon phyllocladoides.
If a large database is available, with data well distributed over time and
space, another approach is possible based on geographical distribution analysis
and its variations in time (palaeobiogeography) and concomitant analysis of the
sediments which yielded corresponding specimens. European fossil wood record
for the Liassic is quite complete and well distributed over time and space, and we
have a fairly good image of Liassic wood flora distribution in Europe (Philippe,
[6]; Philippe et al., [5]). From the distribution data given above it can be noticed
that: 1) X. phyllocladoides is known in Europe from the Planorbis (Hettangian)
to the Retrocostatum (Bathonian) ammonite zone; in southern Europe (France,
Southern Germany) it is found mostly in Late Pliensbachian – Early Toarcian
interval (two thirds of the data synthesized in Table 1) and in the Opalinum
Zone (Early Aalenian); this fits with available stratigraphical information for
Balaban Formation and corroborates its dating as Toarcian; 2) The frequency
of X. phyllocladoides among European Liassic wood assemblages is increasing
northward, and the species is common only in the Arctic; 3) X. phyllocladoides
is commonly found within thick clay levels deposited in anoxic environment.
Xenoxylon is known as an indicator of cool/wet temperate climate (Philippe
and Th´evenard, [6]. It was hypothesized that Xenoxylon occurrences in Southern
Europe were driven by cold and/or wet climatic snaps. This was confirmed for
the Late-Callovian – Early Oxfordian occurrences (Dromart et al., [13]). It is
difficult, however, to be more accurate on how cold and how wet. In the Early
Cretaceous Xenoxylon is supposedly bound to mean annual temperatures (MAT)
in the range of 10 ◦C–15 ◦C (Philippe and Th´evenard, [8]). Xenoxylon stumps
usually reached 1 m to 1.5 m in diameter, with growth-ring width often exceed-
ing 8 mm, sometimes 1 cm (personal observations on a collection of five stumps
of Xenoxylon latiporosum (Cramer) Gothan in Liaoning, PR China). Such quick
growth and massive trunks cannot occur in dry environments, and indicate ei-
ther an amount of annual precipitations above 1 m, or growth in environment
well supplied in phreatic water. For the Jurassic of Eastern Greenland, where
Xenoxylon phyllocladoides was commonly found (Gothan, rn4; our observations),
←
Plate II
Fig. 1. Balaban Formation – sandstones, lower part of the holostratotype section, Toarcian
(Lower Jurassic), Balaban Dere River valley, south of Dobromir Village, Burgas district
Fig. 2. Xenolylon phyllocladoides Gothan. Negative traces of the stems on the upper surface
of sandstone bed, Balaban Dere River valley, south of Dobromir Village, Burgas district
Fig. 3. Location of the Tethyan Mator sediments in East Stara planina on the geological
panorama of the South-east Europe (after Zagorchev [16]
Compt. rend. Acad. bulg. Sci., 61, No 5, 2008 637
palaeoenvironments have been interpreted as wet temperate (Surlyk [14]; Arias
[15]).
Acknowledgements. Frank Wittler is thanked for the opportunity to study
material from Germany, and Gilles Cuny for his help while revising collections
in Copenhagen. Visit to Copenhagen Geology Museum was made possible by the
Synthesis programme. Guillaume Suan and Baptiste Sucheras contributed with
valuable discussions. This publication is UMR5125-07.XXX of the French CNRS.
We greatly appreciated the constructive notes of the two reviewers.
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UMR 5125 (PEPS) CNRS, France
Universit´e de Lyon
Lyon, F-69003, France
e-mail:Marc.Philippe@univ-lyon1.fr
∗Geological Institute
Bulgarian Academy of Sciences
Acad. G. Bonchev Str., Bl. 24
1113 Sofia, Bulgaria
e-mail:platon.tchoumatchenco@gmail.com
638 M. Philippe, P. Tchoumatchenco
... As a fossil wood genus with distinct palaeoclimatic implications, Xenoxylon has been extensively accepted as an indicator of cool and wet climates (Philippe and Thévenard 1996;Philippe and Tchoumatchenco 2008;Philippe et al. 2009Philippe et al. , 2013Oh et al. 2015;Tian et al. 2015Tian et al. , 2016Wan et al. 2016Wan et al. , 2017Boonchai et al. 2020). Analysis of European Cretaceous data suggests that the mean annual palaeotemperature at the Xenoxylon localities was generally below 15°C (Philippe and Thévénard 1996;Philippe and Tchoumatchenco 2008;Philippe et al. 2013). ...
... As a fossil wood genus with distinct palaeoclimatic implications, Xenoxylon has been extensively accepted as an indicator of cool and wet climates (Philippe and Thévenard 1996;Philippe and Tchoumatchenco 2008;Philippe et al. 2009Philippe et al. , 2013Oh et al. 2015;Tian et al. 2015Tian et al. , 2016Wan et al. 2016Wan et al. , 2017Boonchai et al. 2020). Analysis of European Cretaceous data suggests that the mean annual palaeotemperature at the Xenoxylon localities was generally below 15°C (Philippe and Thévénard 1996;Philippe and Tchoumatchenco 2008;Philippe et al. 2013). Liu (2017) and Zhang et al. (2019) utilised ginkgo fossils to reconstruct palaeotemperature and inferred that the temperature of the Baojishan Basin in the Middle Jurassic was approximately 15°C. ...
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... Palynological records (Schnyder et al., in prep.), combined to paleobotanical records can help to decipher paleoclimatic background as some wood taxa are paleoecologically well constrained (Philippe and Thévenard, 1996;Philippe and Tchoumatchenco, 2008;Oh et al., 2015). Recently, δ 15 Norg measured in lignites and clayey layers was used to evidence wet/dry cycles during the Paleocene-Eocene transition (Storme et al., 2012). ...
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... Palynological records (Schnyder et al., accepted for publication), combined with paleobotanical evidences can help to decipher paleoclimatic background as some wood taxa are paleoecologically well constrained (Philippe and Thévenard, 1996;Philippe and Tchoumatchenco, 2008;Philippe et al., 2013;Oh et al., 2015). Recently, δ 15 N org measured in lignites and clayey layers was used to indicate wet/ dry cycles during the Paleocene-Eocene transition (Storme et al., 2012) and the Eocene-Oligocene transition . ...
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Full-text available
  • May 2007
A century ago Gothan described fossil woods from the Arctic and established several new species and genera that were subsequently widely used. The type material has, however, never been reviewed. Investigations in Berlin and Stockholm resulted in the re-location of the original material which allows us to propose lectotypifications for the names of six species recognized by Gothan, three of which represent types of Gothan's generic names, Anomaloxylon, Protocedroxylon, and Protopiceoxylon. The types (holotypes or lectotypes) are illustrated here, some of them for the first time with micrographs. Taxonomic investigation of Gothan's species with "Abietineentüpfelungen", an anatomical feature of ray cells, suggests that Cedroxylon transiens and Anomaloxylon magnoradiatum should be regarded as taxonomic synonyms of Protocedroxylon araucarioides, and Cedroxylon cedroides as a taxonomic synonym of Protopiceoxylon exstinctum.
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Distribution and palaeoecology of the Mesozoic wood genus Xenoxylon: Palaeoclimatological implications for the Jurassic of Western Europe
Article
Full-text available
  • Mar 1996
  • REV PALAEOBOT PALYNO
Xenoxylon is a morphogenus used for a Mesozoic type of wood. Its distribution is circumpolar, limited to the Northern Hemisphere and belt-like. The lower the palaeotemperature, as estimated from geological inferences, the lower is its mean palaeolatitude. The wood is frequently associated with floristic or sedimentological indications of a cool and/or wet climate. Both synecology and autoecology suggest that Xenoxylon favoured cool/wet climates. The sedimentological analysis of its occurrence sheds new light on the relationship between palaeoclimatology and sedimentation.
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The Jurassic system in the Eastern Stara Planina Mountain (Bulgaria). II: Palaeogeographic and palaeotectonic evolution
Article
  • Mar 1990
A reconstruction of the palaeogeographic environment during the deposition of the Lower Jurassic sediments indicates the existence of a turbidite trough infilled with proximal sediments (forming the deep-sea Hadzievdol Fan Delta) and distal basin turbidites. This trough originated as a result of extension during the Pliensbachian and Toarcian. South of it there was a shelf basin bounded on the south by the exotic Zlatarski Ridge. These isopic zones are grouped into a new Early-Middle Jurasic tectonic unit – the Matorids, bordered on the south by the Vardar ocean. The destruction of the Matorids, in conditions of convergence, began during the Aalenian and their main uplift occurred during the Bajocian and in the beginning and the middle of the Bathonian when olistolites of different size were transported into the basin. During the collisional stage, which began in the end of the Bathonian, the areas emerged above sea level – a phenomenon probably related to subduction of the Vardar ocean below the Pontids and their prolongation – the Zlatarski Ridge. At present, in the area of East Stara Planina, the Jurassic sediments form a long and narrow Austrian tectonic structure – Mator Mts. anticline, with preserved northern, southern or in rare cases – both limbs. The contribution is accompanied by 4 appendices which describe in detail the Early-Middle Jurassic dynocysts (Dodekova), miospores (Cernjavska) and foraminifers (Trifonova) in the Luda Kamčija Group. Correlations are also made between Kotel Formation and some Upper Cretaceous olistostrome formations in East Stara Planina and Elena-Tvârdica Stara Planina which were incorrectly referred in the past to the Kotel Formation (Sapunov).
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Ice age at the Middle–Late Jurassic transition?
Article
  • Aug 2003
  • EARTH PLANET SC LETT
A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (δ18O values of shark tooth enamel) indicates a severe cooling at the Middle–Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1–3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle–Late Callovian widespread deposition of organic-rich marine sediments (e.g. northwestern Europe, Central Atlantic, and Arabian Peninsula). This thermal deterioration can thus be ascribed to a downdraw in atmospheric CO2 via enhanced organic carbon burial which acted as a negative feedback effect (i.e. the inverse greenhouse effect). The glacial episode of the MLJT climaxed in the Late Callovian, lasted about 2.6 Myr, and had a pronounced asymmetrical pattern composed of an abrupt (∼0.8 Myr) temperature fall opposed to a long-term (∼1.8 Myr), stepwise recovery. The glacial conditions at the MLJT reveal that atmospheric CO2 levels could have dropped temporarily to values lower than 500 ppmv during Mesozoic times.
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F-69003, France e-mail: Marc
  • Umr Peps
  • France Cnrs
  • Université De Lyon
  • Lyon
UMR 5125 (PEPS) CNRS, France Université de Lyon Lyon, F-69003, France e-mail: Marc.Philippe@univ-lyon1.fr
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  • PALAEOGEOGR PALAEOCL
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  • I Zagorchev
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Zagorchev I. Mitt. Osterreich. Geol. Geselschaft, 86, 1994, 9-21.
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  • REV PALAEOBOT PALYNO
  • 184-207
  • M Bamford
Philippe M., M. Bamford. Review of Palaeobotany and Palynology, 148, 2008, 184-207.