Primary production, isotopes, extinctions and the atmosphere

Triassic palynology of the Carnarvon Basin, Western Australia

Portrait of a Gondwanan ecosystem: A new late Permian fossil locality from KwaZulu-Natal, South Africa

Dinoflagellates are a major component of the marine microplankton and, from fossil evidence, appear to have been so for the past 200 million years. In contrast, the pre-Triassic record contains only equivocal occurrences of dinoflagellates, despite the fact that comparative ultrastructural and molecular phylogenetic evidence indicates a Precambrian origin for the lineage. Thus, it has often been assumed that the dearth of Paleozoic fossil dinoflagellates was due to a lack of preservation or recognition and that the relatively sudden appearance of dinoflagellates in the Mesozoic is an artifact of the record. However, new evidence from a detailed analysis of the fossil record and from the biogeochemical record indicates that dinoflagellates did indeed undergo a major evolutionary radiation in the early Mesozoic.

The early Mesozoic radiation of dinoflagellates

Recent discoveries of palynoflorules at numerous localities in the Newark Group basins of the eastern United States provide new evidence for correlation of deposits in these basins. Floras from the Shuttle Meadow and Portland Formations of the Newark Group rocks in the Hartford Basin of Connecticut and Massachusetts indicate that the Triassic‐Jurassic boundary is located within the rocks of this basin: a shift of Corollina from more than 90% C. meyeriana to more than 90% C. torosus occurs somewhere between the Shuttle Meadow and Portland Formations and generally indicates a Rhaeto‐Liassic age. In the Shuttle Meadow Formation, the overall shape of the palynoflora (particularly the presence of Convolutispora klukiforma), associated fish, paleomagnetic data, and radiometric dates, as well as megafossil evidence of Brachyphyllum scotii and Clathropteris menis‐coides, support a basal Liassic age for this formation. Reptilean evidence in older strata of the Hartford Basin suggests that the Triassic‐Jur...

J. Jansonius

Papers

Palynology of permian and triassic sediments, Peace River area, Western Canada