Anatomically preserved cordaitalean trees from the Pennsylvanian of Yangquan City,Shanxi Province,and their implication for a perhumid climate in North China Block

Fifty-six cordaitalean trunks with anatomical features are discovered and described from the Moscovian (Pennsylvanian) Benxi Formation in Yangquan City, Shanxi Province, North China. They are allochthonously preserved in fluvial channel deposits and classified into two types based on the anatomy. The first type is characterized by a solid and heterocellular pith, endarch primary xylem and pycnoxylic secondary xylem with araucarian radial tracheidal pits and araucarioid cross-field pitting. The second type contains a septate pith and a pycnoxylic secondary xylem which is comparable to that of the first type. Primary xylem is absent in the second type. The diameter of these trunks ranges from 0.11 m to 0.55 m. The largest tree is estimated to be 29.96 m high using an allometric approach. The trunks represent the oldest and largest trees from the North China Block during the Pennsylvanian due to the absence of Silurian, Devonian, and Mississippian there. The fossil evidence shows that cordaitaleans were large arborescent trees growing on clastic substrates in the Cathaysia during the Pennsylvanian. Their occurrence from the upper Pennsylvanian in North China Block suggests that the previously reported diversity of cordaitaleans, which were estimated based on impressions, is a gross underestimate. The absence of growth rings in the trunks and co-occurrence of arborescent lycopsids in the same interval, together with coal seams and bauxite around the fossil-bearing horizons, indicate that the trees grew under perhumid tropical conditions.     

Coralline algae as depth indicators in the Miocene carbonates of the Eratosthenes Seamount (ODP Leg 160, Hole 966F)

The abundance of the major coralline algal groups has been investigated and quantified in the coralline-rich facies of the Miocene shallow-water carbonates of the Eratosthenes Seamount (eastern Mediterranean, off-shore Cyprus). The analysis is based on the quantification of the most easily-recognizable groups of coralline algae in order to provide a user-friendly approach for palaeobathymetric reconstructions. Coralline algal distribution through the core suggests water depth estimates generally similar to those based on the composition of the skeletal assemblage and the benthic foraminiferal association in particular. The only noticeable difference occurs in the rhodolith and coral facies, where algal distribution suggests deeper waters than those indicated by benthic foraminifera. The distribution pattern of the major groups suggests that the ratio between Hapalidiales and Corallinales is the most reliable indicator of water-depth. The comparison with other models available in literature highlights a general zonation useful for the study of tropical, middle to late Miocene oligotrophic carbonates. Very shallow settings (0–20 m) are overwhelmingly dominated by Corallinales; in slightly deeper settings (20–40 m) Hapalidiales are more abundant, especially if the sea-floor is shaded (for example by a macrophyte canopy). Between 40 and 60 m, Hapalidiales dominate but Corallinales are still common, while below 60 m Corallinales are very rare. In non-oligotrophic environments this zonation is not reliable and, due to the reduced water clarity related to the high primary productivity, Hapalidiales clearly dominate even in very shallow settings.