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Re: Cretaceous forests mapped

From: Ben Creisler


The full paper can be viewed at the following link. You need an ID and
password to download it, however:


Another paper on a related topic  that might be of interest can be
downloaded for free. I can't remember if it's been mentioned on the
DML yet. It not yet officially published.

C. COIFFARD and B. GOMEZ (2012)

Influence of latitude and climate on spread, radiation and rise to
dominance of early angiosperms during the Cretaceous in the Northern
G e o l o g i c a   A c t a 1 0 (1):  1 - 8
D O I :   1 0 . 1 3 4 4 / 1 0 5 . 0 0 0 0 0 0 ? ? ?

Our aim is to evaluate the infuence of climate and latitude on the
rise to dominance of angiosperms in space and time during the
Cretaceous. The main objectives of the study are: 1) to determine
whether a relationship existed between  plant  biogeographical
distribution  and Cretaceous  climate  changes;  2)  to  explore
latitude-dependent forcing on early angiosperm ecology; 3) to propose
of a mechanism explaining the observed stages of radiation in early
angiosperms. The study focuses on 18 Cretaceous megafossil localities
and reviews on microfossils in the Northern Hemisphere.
A database has been compiled using literature and personal unpublished
data. The data document occurrences of micro- and megafossil plant
remains including spores, pollen grains, leaves and whole plants. They
are placed in context through the use of Cretaceous geographical maps
and temperature curves or values.
There  is  a  clear  correlation between  latitude  and  the
composition of Cretaceous foras. Latitudinal vegetation belts
fuctuated in concert with climate changes during the Cretaceous.
Differences in original plant associations may have driven the gradual
plant turnover that resulted in the rise to dominance of early
angiosperms during the Cretaceous. Cretaceous climate changes created
dispersal bottlenecks. Bottlenecks induced extinctions of some
plant groups and radiations of others. Those that successfully
radiated continued to spread.

>> 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