Re: Cretaceous forests mapped

[Clair Ossian <clastic@verizon.net>]

If a copy is available, I'd appreciate it.  Thanks


Clair Russell Ossian, Ph.D.
Professor Emeritus, Geology
Tarrant County College
2805 Raintree Drive
Carrollton, TX 75006




On 2/28/12 2:00 AM, "Ben Creisler" <bcreisler@gmail.com> wrote:

> From: Ben Creisler
> bcreisler@gmail.com
> 
> An article in Geology that might interest some DML members:
> 
> Emiliano Peralta-Medina and Howard J. Falcon-Lang (2012)
> Cretaceous forest composition and productivity inferred from a global
> fossil wood database.
> Geology 40 (3): 219-222
> doi: 10.1130/G32733.1
> http://geology.gsapubs.org/content/40/3/219.abstract
> 
> Abstract
> 
> Global patterns of Cretaceous forest composition and productivity are
> analyzed using a comprehensive fossil wood database (n = 2238). To
> ascertain forest composition, records were classified by botanical
> affinity, plotted on georeferenced paleomaps, and analyzed with ArcGIS
> tools. Results confirm previous conjecture that araucarioid and
> podocarpoid conifers were globally codominant in Early Cretaceous
> time, especially in humid tropical and paratropical biomes, but
> drastically reduced in numbers and range during the Late Cretaceous.
> Cupressoid conifers, which were most common in seasonally dry
> mid-latitudes, and pinoid conifers, which were associated with
> temperate conditions at higher northern latitudes, also declined at
> the same time, though less markedly. Spatial analysis suggests that
> the loss of conifer forests (especially araucarioids) was linked to
> the rise of co-occurring angiosperms. Our data also show that while
> angiosperms explosively diversified in mid-Cretaceous time, they did
> not become forest dominants until the latest Cretaceous (25 m.y.
> later), by which time the modern relictual pattern of conifer
> distribution had been established. To ascertain forest productivity,
> mean tree-ring width data were obtained from direct measurements and
> literature reviews (n = 284) and plotted by paleolatitude. Comparison
> with modern data shows that Cretaceous forest productivity was
> significantly elevated (×2) in mid- and high paleolatitudes, implying
> a poleward displacement of the temperate zone by >15°. Our data
> provide quantitative verification of Cretaceous climate-vegetation
> models and improve the understanding of the long-term effects of
> future global warming.
> 
> For a news story:
> http://planetearth.nerc.ac.uk/news/story.aspx?id=1170