Alternative global Cretaceous paleogeography

Abstract

Plate tectonic reconstructions for the Cretaceous have assumed that the major continental blocks-Eurasia,

Dispersals of Hyoscyameae and Mandragoreae (Solanaceae) from the New World to Eurasia in the early Miocene and their biogeographic diversification within Eurasia

“…The ages of Nicotiana and Nolana estimated in different studies suggest that our data are generally comparable with previous findings. The ages of Hyoscyameae and Mandragoreae (17.96 mya and 20.48 mya, respectively) are much younger than the breakup of the Gondwanaland (100-120 mya) (Bauer, 1993;Hay et al, 1999) and thus reject the hypothesis of the Gondwanaland vicariance, which assumes that their ancestors occurred in habitable areas of Gondwanaland and migrated to Eurasia from Africa in the late Cretaceous or in the early Tertiary (Hoare and Knapp, 1997;Symon, 1991;Tu et al, 2005). Instead, the ages of the two tribes and their affinities to the tropical or subtropical American elements support the hypothesis of two independent dispersals of the two tribes from the New World to Eurasia as postulated by Olmstead et al (2008).…”

“…For example, the classical trans-Atlantic distributions of many plants have been considered associated with the breakup of Africa and South America (Raven and Axelrod, 1974;Wu et al, 2003). However, these two landmasses separated from each other 100-120 million years ago (mya) (Bauer, 1993;Hay et al, 1999), and vicariance may be appropriate only to interpret the distributions of some anciently diverged plant taxa, such as Annonaceae and Alstroemeriaceae -Luzuriagaceae, that were dated to Cretaceous (Doyle et al, 2004;Vinnersten and Bremer, 2001). Many plant taxa disjunct between Eurasia and North America may represent elements of the once continuous Arcto-Tertiary or boreal floras in the Tertiary (Li, 1952;Tiffney, 1985;Tiffney and Manchester, 2001).…”

Biogeography and divergence times in the mulberry family (Moraceae)

“…The prevailing view is that the Madagascar-India-Seychelles land mass rifted northward from Antarctica »132 mya, that Madagascar separated from India 84-95 mya, and that India drifted northward to collide with Asia approximately 43-50 mya (McLoughlin, 2001;Sanmartín and Ronquist, 2004). An alternate view proposes a land connection between Madagascar-India-Seychelles and Antarctica until as late as 80 mya (Hay et al, 1999). Dates for the separation of Australia from Antarctica range from 35 to 50 mya (McLoughlin, 2001;Woodburne and Case, 1996), followed by the split between South America and Antarctica (»35 mya).…”

Thermal, hydrous, and mechanical states of the mantle transition zone beneath southern Africa

“…For a moving plate, the downwelling is expected to leave a track of cold mantle within the transition zone in the direction of plate motion (Fig. 6a) [53,54]. Thus, if the downwelling mantle has temperature and compositional anomalies large enough to cause the variations in the depth to the 660-km discontinuity, it would produce a swath of anomalously thick transition zone that runs parallel to the track of plate motion.…”