Terrestrial Palaeoecology and Global Change

Chapter 5. Tectonic factors of global changes
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have been owing to juxtaposition of terrains from different latitudinal zones. However, this
explanation does not hold for Primorye, where the early Neocomian flora was of a Tetori
aspect, with Dictyozamites kawasakii and D. falcatus prominent among the bennettites,
while the subsequent Aptian to Albian assemblages varied across the incipient Sikhote Alin
Ranges. The lee side assemblages were rich in bennettites and brachyphyllous conifers
representing open xeromorphic vegetation. Those of the see-facing slope were of a conifer
rainforest type fringed by the coastal fern marshes. Coal accumulation was much
thicker in the foredeep than in the inland basins, with resinites characteristic of the latter.
The late Albian redbeds are also confined to the inner zone.
Thus, both the vegetational and sedimentary features indicate rain shadow over the lee
side of the coastal ranges. In the early Neocomian, the rain shadow covered the inner zone
of Japan as well as the eastern Primorye. Uplifts that cast this shadow might have developed
over the midline fault zone of Japanese Islands that were then part of the continent.
A radical change has occurred since the Late Neocomian tectonism, a major thrusting
phase of Pacific margin. The Permian to Jurassic reefal limestones and cherts were
emplaced over the axial fault zone of the incipient Sikhote Aline ranges (Krassilov &
Parnyakov, 1987; Kemkin & Filippov., 2001). The overethrusts might have been rooted
in the uplifted landmass east of Primorye, including the Yamato Rise (emergent in the
Cretaceous, with Classopollis pollen assemblages coming from an inner zone vegetation:
Markevich, 1994) and the cratonic foreland of Honshu. Before the thrusting event,
the rain shadow over eastern Primorye was conceivably cast by this landmass. It was
removed with a displacement of the Yamato – Honshu landmass over the NNE striking
dextral strike-slip fault system. A series of heterochronous pull-apart basins has developed
in between, with a stepwise oroclinal bend of Japan arc commencing in the Early
Cretaceous, 120 Ma (Uyeda & Miyashiro, 1974) and intermittently continuing until the
Miocene (Ito, 2001). Rainforest and wetlands spread over the coastal plains of the arising
backarc basin, while the rain shadow was displaced to the inland basins west of the
rising orogenic structure over the Neocomian overthrusts (Fig. 75).
V.9.2. Land connections and gateways
Floristic similarity is evidence of a nascent or recent land connection. The Angarian
lepidophytes occur in the Carboniferous of Brooks Range, Alaska (Thomas & Spicer,
1986). The Cathaysian elements are found in the Permian flora of western North America
(IV.3). The Cretaceous – Palaeocene floras of eastern Asia and western North
America share virtually all their dominant species of conifers and angiosperms, both
terrestrial and aquatic (Taxodium olrikii, Metasequoia occidentalis, Trochodendroides
arctica, Nordenskioldia borealis, Platanites raynoldsii, Viburniphyllum finale,
Limnobiophyllum scutatum, Quereuxia angulata, etc., see Krassilov, 1976a, 1979;
Tiffney, 1985; Manchester, 1999). These floristic data confirm at least intermittent trans-