USGS Open-File Report 94-023
Landscape And Climate Of The Southwestern Russian Plain In The Pliocene
- Tanya V. Svetlitskaya
- Russian Academy of Sciences, Moscow, Russia
Along the northern coast of the Black sea on the southwestern Russian
Plain, interbedded continental and marine sediments cover the entire
Pliocene. The fossil floras and faunas of these deposits have been
studied in detail, providing the basis for paleoclimatic interpretations
and biostratigraphic correlations. This report discusses the most
complete sections from this region, concentrating on sites where there are
distinct boundaries between stages and horizons and where there are
abundant paleontological data from marine mollusks, gastropods, ostracodes
and terrestrial mammals and palynological data. The Pliocene of this
region is divided into three stages (based on paleontological assemblages)
which are (from older to younger) the Pontian, Kimmerian, Kuajlnician.
Nine sections were studied from fluvial terraces above the flood-plains of
the rivers Byk and, Kuajlnik; from the coastal terrace scarps above
Khadzibejsky bay and from the Kertch peninsula of Crimea (Fig. 1).
- Figure 1. Pliocene localities on the Southwestern Russian
Plain
- This figure is available as a
GIF,
PICT,
or
TIFF (line-art) image.
Paleomagnetic studies for each of these sections were carried out in
Laboratory of the Moscow University following the method of A. Khramov and
L. Cholpo (1967). Paleoclimatic reconstructions are based on
paleofloristic data from the above mentioned sections studied by S.V.
Siabraj and on published materials from adjacent regions (A. Negru (1986),
S. Medianik (1985), and N. Shchekina (1979) The methodology used to
estimate paleoclimatic conditions on the basis of fossil floras was
developed by V. Grichuk (1987), following the concepts of J. Iversen
(1941) and modified to be applied to Tertiary floras. In the following text
I present paleogeographical reconstructions developed from our
paleomagnetic and paleofloristic research, combined with previously
published information.
Pontian Stage (5.4-4.7 Ma)
During the Novorossijskoe substage, at the beginning of the Pontian age,
the Zanklian transgression united the Black and Caspian Seas with the
Mediterranean. By the end of early Pontian time (~5.0 to 4.9 Ma?) the sea
retreated southwestward and the greater part of the southwestern Russian
Plain was exposed.
Marine faunas indicate that the early Pontian sea was closed and
brackish. The mollusks assemblages from these deposits include Unio and
Anodonta, while the ostracode fauna includes Caspiella, Bakunella and
Leptocythere. From these data Ivchenko (1986) estimated that the mean
annual water temperature was near +12° to +15°C (today near the city of
Odessa the mean annual water temperature is +9.6°C). In the early Pontian
forest-steppe prevailed in the western part of the region under
investigation -- pine forests grew in the river valleys, and the northern
part was occupied by mixed conifer-broadleaved forests.
By the middle of Novorossijskoe time some aridification had taken place in
the east and the role of open vegetation communities increased.
Chenopodiaceae were important in these communities and possibly these
included halophytes, which may have occupied the recently exposed Black
Sea shelf.
In the west such changes of the climate were not registered and forest-
steppe vegetation continued to grow. By the end of this period forests
dominated in both the east and in the west. These were primarily broad-
leaved formations with Ulmus, Zelkova, and Fagus. The climate was similar
to the contemporary climate of the southern Crimea coast, but the presence
of exotic taxa suggest that it was something warmer than today (January
mean temperature ~ +5°C and July ~ +25°C)
The Pontian stage of the history of the Hipparion fauna is poorly
represented in the former USSR. Only scattered small occurrences of
mammals bones have been found in southern Ukraine. This "Tauric complex"
(Korotkevich, 1988) includes the first occurrence of Paracamelus, while
typical members of the Hipparion fauna were not present at this time. The
increased abundance of ostriches suggests greater availability of open dry
areas. However, the presence of certain water-swamp birds and tortoises
points to the development of marshlands and warm-water environments,
whereas the abundance of Cervus and Proboscidea indicate the presence of
wooded vegetation. On the whole, this faunal assemblage reflects
moderately warm and relatively dry climate.
Kimmerian Stage (4.7-3.4 Ma)
In the middle Pliocene more land was exposed and sea waters were confined
to within the limits of the modern Black Sea and Caspian Sea depressions.
The Kimmerian Black Sea basin was closed with brackish water. The marine
fauna of this period included Dreissenidae, Cardiidae, endemic gastropods,
Viviparus, Melanopsis, Planorbis and the freshwater ostracodes Caspiela
and Caspiocypris. The majority of the marine fauna had a boreal character
with few Mediterranean taxa. At this time the broad-leaved forests were
composed mostly of heat-loving and moderately heat-loving species: Acer,
Quercus, Juglans, and less common Castanea, Morus, Carya, Fraxinus, and
Tilia. By the end of this period the proportion of steppe elements
increased and steppe and forest-steppe landscapes appeared. Paleobotanic
data from middle Kimmerian sediments indicate a warmer and more humid
climate than previously. During the first half of the Kimmerian, the
percentage of subtropical genera in the flora (Pittosporum, Parrotia,
Nyssa, Aralia, Magnolia, Staphylea, Taxodium) increased over the levels
seen during late Pontian, suggesting that temperatures had increased. The
maximum temperature increase occurred during deposition of the sediments
of the Kamyshburun horizon (4.2 - 4.0 Ma). Mean January temperature rose
by almost 2°C (to 6°C) and mean July temperature rose from 22°C to 23°C.
The Kuchurganian and Moldavian faunal complexes that developed during the
Kimmerian time indicate the progressive aridification. The earlier
(Kuchurganian) included in its composition the main elements of the
Hipparion fauna: Deinotherium, Zygolophodon, Hipparion, and Tapirus, and
is largely dominated by forest and forest-steppe species. The Moldavian
faunal assemblage reflects the progressive drying of the climate: taxa
characteristic of humid environments disappear and inhabitants of open
areas such as Paracamelus and Equus (which makes the first appearance
here) and more moderate climate appear (Korotkevich, 1986). The climate
was apparently humid and moderately warm (January - above +4°C; July ~+22°C).
Kuajlnician Stage (3.4-2.3 Ma)
In the late Pliocene this region was an elevated plain on which the modern
river network was formed. the sea basin remained only at the south of the
area. It was a closed basin with brackish water , but its salinity was
less than in Kimmerian time. The marine fauna was inherited the main
features of Kimmerian fauna, but was less diverse. The mollusks
Limnocardium, and Dreissena appeared during the Kuajlnician, and
gastropods were represented primarily by the fresh-water forms Planorbis,
Valvata, and Melanopsis. Ostracodes include the typically fresh-water and
brackish-water taxa Cypria kurlaevi and Cyprideis.
Mixed conifer/broad-leaved forests grew along the northern Black Sea coast
at the beginning of this time, suggesting more humid conditions than
earlier. Acer, Tilia, Fagus, and Quercus grew with more thermophilous
trees such as Pterocarya, Zelkova, Fraxinus, Morus, and Juglans. To the
east relatively moist steppe vegetation was present. Compared with that of
the Kimmerian, the terrestrial vegetation of Kuajlnik time had lower
representations of broad-leaved trees and higher levels of steppe taxa.
The climate was rather warm and humid, with mean January temperature near
+4°C and July mean temperature near +22°C.
A substantial reduction of the forest area occurred at the end of the
Kuajlnik time, and among the remaining trees pine and dark-coniferous
types (Picea, Abies, Tsuga, etc.) prevailed. The diversity and number of
broad-leaved trees and other warmth-loving species decreased. Pollen
spectra of Kuajlnik deposits are close in composition to those of the
early Pleistocene and only rare pollen grains of Myricaceae, Moraceae,
Rutaceae and Taxodium allow us to assign these deposits to the Pliocene.
Collectively, these data point to an intensification of aridification and
a decrease in temperature.
This is the time of the appearance of the Chaperon faunal assemblage which
includes many modern elements. Warmth-loving animals (giraffes, Tapirus,
Deinotherium) disappeared by this time and the warm-moderate types (apart
from Archidiscodon, Equus, Cervus, Dicerorinus etruscus, etc.) occured
more widely (Korotkevich,1988). Fauna data indicate arid climatic
conditions and small mammal assemblages indicate steppe vegetation. The
climate was apparently dry with moderately warm temperatures (January
about +4°C; July +22°C).
Conclusions
In the beginning of the Pliocene forest-steppe vegetation covered most of
the southern Russian Plain. By middle Pliocene time temperate broad-leaved
forests begin to prevail, and by the late Pliocene increasingly arid and
cold conditions led to more open landscapes with steppe and forest-steppe
vegetation. The warmest climates of the Pliocene occurred in middle
Kimmerian time (~4.2 to 4.0 Ma), but warmer than modern conditions
continued until approximately 2.5 Ma.
References
- Grichuk, V.P., Zelikson, E.M., and Borisova, O.K., 1987, Reconstrukcia klimaticheskich pokozatelej rannego Kajnozoja po paleofloristicheskim dannym (The reconstruction of the climatic parameters of early Cenozoic by paleofloristic data), in Klimaty Zemli v geologiceskom proschlom (Climates of the Earth on the geological past): Nauka, Moscow, p. 69-78.
- Iversen, J., 1944, Viscum, Hedera, and Ilex as climate indicators: Geol. fören. Stockh., förh., v. 66, p. 463-483.
- Khramov, A.N., and Cholpo, L.E., 1967, Paleomagnetism, Nedra, Leningrad, 252 p.
- Korotkevich, E.L., 1988, Istoria formirovania hipparionovoj fauny Vostochnoj Evropy (The history of Hipparion fauna formation in the East Europe): Naukova Dumka, Kiev, 160 p.
- Medianik, S.I., 1985, Palynologicheskaya harakteristika ponticheskich otlozenij u s. Vinogradovka, Moldavoskoj SSR (The palynology characteristics of Pontian sediments near village Vinogradovka, Moldavskaya SSR): Proceedings of the Academy of Science of Modvava, v. 10, p. 55-58.
- Negru, A.G., 1986, Poznemiocenovaya flora jugozapada evropejskoj tchasti SSSR (po paleocarpologicheskim dannym) (The floras of the late Miocene of the Southwestern European part of the USSR (on the paleocarpological data)) [abs.]: Doctor's Thesis of Biology, Kischinev, 49 p.
- Shekina, N.A., 1979, Istoria flory i rastitelnosti juga evropeiskoj chasti SSSR v pozdnem miocene-rannem pliocene (The history of flora and vegetation of the South European of the USSR in late Miocene-early Pliocene): Naukova Dumka, Kiev, 197 p.
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