Terrestrial Palaeoecology and Global Change

Chapter 4. Palaeoecogeography
119
VI.3.3. Mid-Cretaceous biomes
Phoenicopsetea dominated the Arcto-Mesozoic realm from the mid-Triassic to mid-
Cretaceous (although Phoenicopsis itself locally survived until the Maastrichtian) and
was then replaced by the conifer forests with Parataxodium and platanophyllous angiosperms
(the major localities of northern Siberia, Kolymo-Chukotskian region, northern
Canada and Alaska). Wood anatomy, with wide growth rings, few false rings, narrow
late wood increments suggest a temperate climate with a light seasonality along the
northern border (Parrish & Spicer, 1988). The thermophilic producers of Classopollis
and, later, Proteacidites pollen types scarcely penetrated this northern zone. However,
dinosaur localities from Svalbard, the Koryak Highlands (Nessov & Golovneva, 1990),
Arctic Canada and Alaska (Davies, 1987) attest to a circum-polar distribution of this
group. Siliceous Cretaceous sediments of the Arctic Ocean indicate an essentially icefree
climate.
To the south, the deciduous forest type gave way to the semi-deciduous Lauro-Sequoietum
with platanophylls as riparian/seral elements (Sakhalin, Amurland, southern
Siberia, northern Kazakhstan, northern Europe, northern Rocky Mountains, South Greenland).
Within this broad zone, fossil plant localities of the circum-Pacific belt, Atlantic coast
of North America and northern Europe are distinctive on account of exceptionally high
conifer diversities: 15 genera in the Aptian to early Albian flora of Primorye (Krassilov,
1967a) and a comparable number in the Potomac (Berry, 1911) and Scandinavia (Srinivasan
& Friis, 1993), perhaps representing an analogue of the present-day montane
coniferous rainforest. In the phytogeographic scheme of Cretaceous biomes that is further
considered in VII.2.3, this submeridional zone is extended to southeastern Asia on
account of Sequoia finds in Khorat Series of Thailand (Kon’no, 1963).
The compound palmato-pinnate Sapindopsis–Debeya leaf morphotypes are common
over the warm-temperate zone, gradually increasing to dominance, in parallel with
the narrow-leaved laurophylls (“Proteoides”), in the adjacent xerothermic zone extending
over central Europe (Kvaèek & Knobloch, 1967), northern Africa (Lebanon: Krassilov
& Baccia, 2000) and Caspian region to northern China (Guo, 1985, 1996). The Cretaceous
palm records associated with xerothermic zone extend to Vancouver and northern
Japan Islands. Notably, the northern limits of warm-water foraminifera reach to
Vancouver in the Pacific (McGugan, 1982) and to Orphan Knoll in the Atlantic (Berggren
& Hollister, 1977), and that of rudist mollusks (Philip, 1972) nearly coincides with
the temperate/subtropical phytogeographic boundary.
The mid-Cretaceous floras of Crimea (Krassilov, 1984), Central Asia (Samsonov,
1970), northern Africa, India (Barkar & Chiplonkar, 1973), central China, southeastern
Asia (Kon’no, 1963) and southern North America fall into the xerothermic zone but
differ in an absolute preponderance of scale-leaved coniferoids. Occasional records of
scale-leaved assemblages (single-species, of shed leaves, as described in Krassilov, 1978a)