OJG  Vol.9 No.10 , September 2019
The Cretaceous Period of Weather Similar to the Present One and Its Diverse “Conchostracan” Fauna
Abstract: Cretaceous System is widely represented in South America from northeast Brazil to southern Patagonia Argentina. It is characterized by having been a relatively warm climate, with rainfall and marked seasonality which allowed the development of the “conchostracan” populations.

1. Introduction

The Cretaceous Period was a period with warm climate [1] , with increasingly high sea levels in the epicontinental seas. The average global temperature was near to 18˚C [2] . Despite the greenhouse character of the period, the cooling trend towards the Maastrichtian and the 116 Ma “cold snap” triggered the interest in possible continental Cretaceous glaciations [3] .

2. Cretaceous Climate and Bearing “Conchostracan” Faunas

In the Lower Cretaceous, the monsoon circulation of the Pangea culminated, due to the opening of the Atlantic Ocean [4] . The cool interval in the Early Cretaceous is followed by warming lasting until the late Albian [5] . In the continental regions there were changes in atmospheric circulation. Wetter conditions developed and paleoprecipitations increased in tropical areas [6] . Oceanic and continental data suggest equatorial paleotemperatures similar to the present-day [7] . This time was characterized by the presence of areas with prevailing microclimates. In intracratonic basins (e.g. northeast Brazil), the climate was arid with warm-hot temperatures. This type of arid climate, with heavy rainfall, generated favorable seasonal conditions for the development of a diverse “conchostracan” fauna. Wind patterns shew seasonality leading to more extreme climates over the continents. During the Upper Cretaceous warm weather prevailed, with greenhouse periods, globally averaged temperatures were 6˚C - 14˚C higher than today [8] . The paleoprecipitations increased as a result of the end of the monsoon circulation [9] . In Argentina, the conchostracan bearing units as the Lagarcito Fm. (Lower Cretaceous) was interpreted as a deposit of a shallow and perennial freshwater lake in a semi-arid climate [10] . The Cañadón Calcáreo Fm. (Upper Jurassic - Lower Cretaceous) was referred by [11] to sequences represented swampy areas, with a rich and diverse conchostracan fauna in subtropical seasonal dry climate. In Brazil-Uruguay the units are, the Botucatu Fm = Tacuarembó Fm (Late Jurassic - Early Cretaceous), indicating desert climate [12] . The Santana Fm. (Lower Cretaceous) represent tropical climate with highly dependent on the rainfall in the mating epoch [13] was, favorable to establish “conchostracan” populations. The Bauru Basin (San Carlos Fm) the climate was hot and arid [14] . The climate was warm and very dry, probably desert [14] .

3. Conclusion

Finally, the climatic characterization for the Cretaceous of South America, summarized as a warm climate with rainfall and marked seasonality, allowed the development of the “conchostracan” populations so far recorded.


This is a contribution to UNESCO-IUGS IGCP Project 679.

Cite this paper: Gallego, O. , Monferran, M. , Jiménez, V. , Zacarías, I. , Armella, C. , Nieto, D. and Cabaleri, N. (2019) The Cretaceous Period of Weather Similar to the Present One and Its Diverse “Conchostracan” Fauna. Open Journal of Geology, 9, 704-706. doi: 10.4236/ojg.2019.910080.

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