Abstract: The Late Devonian - Early Carboniferous paleobiogeographic pattern is characterized by the immlgration-emim'ation events of Tethyan ...
LATE
DEVONIAN
- EARLY
PALEOBIOGEOGRAPHY FERA
AND
CLIMATIC
OF
CARBONIFEROUS BENTHIC
FORAMINI-
dT
Acont Projeribc!ution
to
GLOBAL BIO
OSCILLATIONS
-
EVENTS
KaLVODa, Jiri *)
Abstract: The Late Devonian - Early Carboniferous paleobiogeographic pattern is characterized by the immlgration-emim'ation events of Tethyan tropic-subtropic foraminiferal fauna which are believed to reflect the major c~matic oscillations. A certain regularity of the outlined oscillations raises the question of the periodicity of the initial events. The extinctions at the Frasnian-Famennian and Devonian-Carboniferous boundary appear to be stepwise affecting preferentially tropic-subtropic fauna which is gradually replaced by the temperate one. They are thus in general similar to the Cretaceous-Tertiary or Eocene-Oligocene extinction.
INTRODUCTION
Recently the major role of climatic change as a prominent cause of marine mass extinction seems to gain a broad acceptance not only in the studied Late Devonian interval (Copper, 1977, 1986; McGhee, 1982; Kalvoda, 1986) but also generally as an important factor in most of the mass extinctions (Stanley, 1984;
Kauffman,1986). The climatic oscillations on the one hand cause a chain of events in the oceanic system (Wilde & Berry, 1986); on the other hand, they are comaeeted with the initial cause (Walliser, 1986). In ore' contribution we shall concentrate on the direct influence of temperature changes on the biogeographie distribution of benthle foraminifera and shall then try to discuss the broader implications of the outlined pattern.
THE
PALEOBIOGEOORAPHICAL
THE
LATE
DEVONIAN-
LOWER
DEVELOPMENT
OF BENTHIC
FORAMINIFERA
IN
CARBONIFEROUS
The composition of benthic foraminiferal assemblages is a very sensitive indicator of the water temperature (Saidova, 1975; Murray, 1987") and the study of the dispersal of benthic foraminifera thus represents a very useful tool for the deciphering of climatic oscillations in the past. Following the differences in the composition between the recent shelf benthic foraminiferal assemblages of the tropic-subtropic belt and of the temperate and boreal higher latitudes (Saidova, 1975; Lukina, 1975; Yuferev, 1978; Murray, 1987) we can broadly distinguish in the studied interval the tropic-subtropic Tethyan Realm and the temperate-boreal North American and Siberian Realm. The Late Devonian-Early Carboniferous paleobiogeographic pattern is characterizcd by emigration-imm@'ation events of the Tethyan fauna as well as by periods of the worldwide predominance of taxa with temperate and/or euryfacial ranges. The Upper Frasnian was characterized by a worldwide distribution of the Tethyan fauna that parallelled the worldwide distribution of reef ecosystems. The deellne of this fauna in the Lower Fameanian was stepwise (Kalvoda, 1986) and was marked by the preferential survival of taxa with temperate affinity. The concentrated impact in the tropics thus seems to indicate some kind of refridgeration (Stanley, 1984).
*) Mikropaleontologick6 odd~lent, Moravsk6 naftov6 doly, 695 30 Hodonfa, Czechoslovakia
184 The first Famennian diversification can be traced only in the Tethyan Realm in the beginning of the Middle Famennian. It was followed by a period of further cooling (Kalvoda, 1986). The greatest Famennian diversification of the Tethyan fauna accompanied by the migration into the temperate Siberian Realm can be traced in the late Upper Famennian. It seems to indicate the climatic optimum for this period. The stepwise worldwide decline of the Upper Famennian Tethyan fauna was again characterized by the preferential survival of taxa with temperate to boreal affinity and seems to represent a second refridgeration event. The radiation and the restoration of the high diversity assemblages in the Middle Tournaisian was recorded mainly in the Tethyan Realm and is compatible with climatic warming in this realm. The Middle/Upper Tournaisian boundary interval is characterized by the considerable decline in the diversity of foramlnlferal fauna and the extinction of the ChernyshineUa fauna. The Upper Tournalsian with the widespread migration of the Tethyan elements both in the Siberian and the North American Realm seems to represent the Tournaisian warming climax.
THE
NATURE
OF
FAMENNIAN
AND
THE
EXTINCTIONS
OF
FORAMINIFERA
DEVONIAN-CARBONIFEROUS
AT
THE
F R A S N I A N -
BOUNDARY
The most important data from the Famennian-Frasnian boundary seems to be from Eastern Europe. The Frasnian benthic foraminifera as well as other benthic forms are found in the Askyn and Evlano-Liven Horizon which are correlated by Ovnanatova and Kononova (1984) with the conodont triangularis Zone and by Rzhonsnitskaya (1986) with the lower part of the triangularis Zone, thus being Famennian in age. However, it should be emphasized that the detailed data about the relation of conodont occurrences and of benthic fauna occurrences has not yet been published.
NORTH AMER. TETHYAN REALM REALM
SIBERIAN REALM
The Upper Frasnian was characterized by the occurrence of advanced forms of benthic foraminifera as
Multiseptida, Eogeinitzina, Eonodosaria, NaniceUa• These Tethyan elements ° ' . ' °0°°. ' .°' o0 ' ° ,°0° ° o° tp.. , ' 0~
z
E
. . . . . . . . . . .
z
,oO.Oo,
z
