Terrestrial Palaeoecology and Global Change

Chapter 5. Tectonic factors of global changes
163
By the mid-Cretaceous, the volcanic activity has spread over oceanic fault zones
forming plateaux and ridges in the Atlantic (the Rockall Plateau, J-anomaly Ridge,
Newfoundland Ridge, Walvis Ridge, Rio Grande Rise, etc: Hekinian, 1972; Humphris &
Thompson, 1983; Hanisch, 1984), eastern Indian Ocean (the Ninety East Ridge, Broken
Ridge, Kerguelen Plateau, etc.: Guilfy, 1973; Hekinian, 1974; Dosso & Vidal, 1979; Mutter
& Cande, 1983) and Pacific (the Emperor Ridge, Tuamotu – Line island chain, Neccer
Ridge, Shatsky Rise, Hess Rise, Magellan Rise, Manihiki Plateau, etc.: Jackson &
Schlanger, 1976; Jenkyns, 1976; Saito & Osima, 1977; Orwig & Kroenke, 1981; Vallier
et al., 1981; Thiede et al., 1981; Kogan et al., 1983; Neprochnov et al., 1984). Whatever
the position of these sutures relative to alleged plate boundaries, their igneous activity
was synchronous with the admittedly “intraplate” volcanism, e.g. of Nauru Basin in the
Pacific (Batiza et al., 1980).
The mid-Cretaceous oceanic events correlate with ophiolite emplacements in the
western Mediterranean, Lesser Caucasus and Tibetan thrust belts, as well as with initiation
(in the Albian) of the circum-Pacific terrestrial volcanic belt developing over the
allochtonous arc/trench complexes thrust upon continental margins (Krassilov, 1989b).
The circum-Pacific thrust belts were granitized by polyphase intrusions, with a distinct
Late Cretaceous phase also recorded in the Trans-Himalayan belt (Huang, 1984).
The Cretaceous/Tertiary phase is marked by a major intracratonic rifting/trap magmatism
event (in particular, by Deccan traps, about 65 Ma: Mahoney et al., 1982; Subbarao,
1999). Most vigorously in the Trans-Himalayan belt, but also in the circum-Pacific,
peri-Atlantic and peri-Arctic belts, the nappe piles were re-thrust, with the granitoid
basement of volcanic arcs emplaced upon the fore-arc flysch trough and melanges (as in
the Sierra Nevada Batholite/Great Valley turbidites/Franciscan melanges of California
or the Ladakh Batholite/Kokhistan Arc/Shyok melanges in the Himalayas: V.6.5). Thus
thickened, the fold belts were isostatically raised as mountain ranges, with a major orogenic
event in the Middle/Late Eocene recorded in the Himalayas, as well as over the
Caribbean, the Canary – Cape Verde belt of eastern Atlantic, the Brooks Range in
Alaska, and elsewhere (V.6.3 -V.6.5).
V.8. Summary of tectonic factors
Spatial distribution of tectonic processes is non-random, governed by the planetary
fault system comprising the orthogonal and diagonal subsystems. Regularities of the
fault network pertain to the rotation-induced stresses.
Distribution of the latter over the globe inflicts antithetic activity of the high-latitude
and low-latitude fault systems. Extension over the northern North Atlantic – Arctic
Ocean coincides with compression over the Tethys.
Although the presently active global lineaments, such as oceanic fracture zones,
are appreciably offset against their preceding Cretaceous and older structures, the