Third (equatorial) desert belt during Mesozoic era?

[onomatomanic]

Hi board,

I've just been reading up on the basics of meteorology, and http://en.wikipedia.org/wiki/Atmospheric_circulation" this claim:

In the extremely hot climates of the Mesozoic, indications of a third desert belt at the Equator has [sic] been found; it was perhaps caused by convection.

Unfortunately, no further information or references are provided, and the only google hits for "third desert belt" point right back to the article.

I can't make sense of it on my own; naively, the mechanism that is responsible for today's equatorial rainforests (maximum insolation -> air is heated -> air rises -> condensation -> precipitation) should function irrespective of whether the climate is, globally, extremely hot or extremely cold, no?

Any elucidation (including "it's nonsense") would be appreciated!

 

[Evo]

Don't forget that during periods of the mesozoic the continenets were inm much different places. What exactly are you asking about?

Maps of Earth's mesozoic period.

http://www.dinosauria.com/dml/maps.htm

 

[onomatomanic]

What exactly are you asking about?

That's just it, I can't give you any context for that claim, I'd just like to understand it. To me, "third desert belt at the equator" sounds like they are referring to the simultaneous existence of three desert belts at some point during the Mesozoic, one centered on 0 degrees latitude, and the other two (presumably) in the familiar places, i.e. stretching from the http://en.wikipedia.org/wiki/Subtropical_ridge" towards the equator.

One would assume that they corrected for continental drift, otherwise, the claim becomes trivial. *shrug*

So, I'm mainly hoping that someone has heard of something like this before and can supply me with the missing context, so that I can then answer your question.

 

[Ophiolite]

According to http://www.ldeo.columbia.edu/~polsen/nbcp/modeldis.html" "virtually all of the models depict a "Hot House" Pangea with a dry equatorial zone, except were large mountain ranges and plateaus are specified." For example:

Allen. J. R. L., Hoskins . B . J., Sellwood. B. W., Spicer, R. A., Valdes, P. J. (eds.), 1994, Palaeoclimates and their modeling; with special reference to the Mesozoic era. Chapman & Hall. London, 140 p.


Parrish, J. T., 1993, Climate of the supercontinent Pangea. Journal of Geology. 101: 215-233.

Chandler, M. A., 1994, Depiction of modern and Pangean deserts: evaluation of GCM hydrological diagnostics for paleoclimate studies. GSA Spec. Pap. 288, 117-138

etc.

However, as the aforementioned article points out "in fact, this [equatorial desert]is in direct conflict with the recent "discovery" that Late Triassic Pangea had tropical precipitation and evaporation gradients were not especially different than today's with a distinct wet equatorial region, even deep within Pangea."

Olsen, P.E. and D.V. Kent, 2000, High resolution early Mesozoic Pangean climatic transect in lacustrine environments, in Bachmann, G. and Lerche, I. (eds.), Epicontinental Triassic, Volume 3, Zentralblatt fur Geologie und Palaontologie, VIII: 1475-1496.

Kent, D. V. and Olsen, P. E., 2000, Magnetic polarity stratigraphy and paleolatitude of the Triassic--Jurassic Blomidon Formation in the Fundy basin (Canada): implications for early Mesozoic tropical climate gradients. Earth And Planetary Science Letters, v. 179, no. 2. p. 311-324.


You might want to search Google Scholar for "Mezozoic equatorial desert climate" for a further 2,130 hits.

 

[onomatomanic]

Excellent, I thought it might just be a matter of getting the search terms right. Thanks!

Without having looked at the papers, the excerpt you posted sounds more like there would have been a single vast desert belt, stretching from ~30 degrees North to ~30 degrees South. Will read up and report back.