EARLY CRETACEOUS ICE AGES FROM WEATHERING AND BIOMASS OF MIGRATING ANGIOSPERMS

The Early Cretaceous, Wonthaggi and Eumeralla Formations of Victoria, Australia, include frigid paleosols (Gelisols) with clastic dikes (ice wedges), load casts of mud (periglacial convolutions), and coal-mantled stone-rolls (aapamires), at the same early Hauterivian and late Barremian levels as dropped pebbles and glendonites in marine rocks of South Australia, New South Wales, Svalbard, Nunavut, and Barents Sea. These permafrost paleosols represent fern-lycopsid tundra and coniferous taiga vegetation, but alternate with non-calcareous Histosols and Ultisols, indicative of humid temperate ecosystems at times of Early Cretaceous greenhouse spikes, revealed by stomatal index of fossil ginkgo leaves, by black shales of oceanic anoxic events, marine transgressions, and both marine and non-marine carbon isotopic anomalies. The greenhouse spikes are widely attributed to massive volcanic eruptions, causing volatility in global carbon dioxide levels, rather than a protracted supergreenhouse, but what caused the ice ages? A key biological innovation of early angiosperms enabling their spread to high latitudes, including Victoria during the Early Cretaceous, was their abbreviated life cycle without extended megagametophyte development within the seed, thus enabling rapid colonization of coastal regions disturbed by large sea level changes and greenhouse warm spikes. Silicate substrates more quickly colonized by plants than before, especially in polar regions with abundant fresh minerals, rapidly built biomass and consumed atmospheric carbon dioxide during weathering from feldspathic sandstone to clay and coal seen in Early Cretaceous paleosols of Victoria.