Palaeoenvironment and ecology of the middle Cretaceous Grebenka £ora of northeastern Asia

• Main Authors: Robert A. Spicer A, Anders Ahlberg B, Alexei B. Herman A C, Simon P. Kelley A, Mikhail I. Raikevich D, Peter M. Rees A E
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2000
• Subjects: Cretaceous; northeastern Russia; palaeobotany; palaeoenvironment; palaeoecology; palaeoclimat; Grebenka; North Pole; Ora
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.521.7099; http://www.geo.arizona.edu/~rees/2002-5.pdf

The Grebenka flora, from the main exposure of the Albian^Cenomanian Krivorechenskaya Formation in northeastern Russia, represents a range of plant communities from pioneer to mature forest that grew close to the mid-Cretaceous North Pole (s 72‡N). The diversity of this flora is dominated by angiosperms followed by conifers, ferns and other plant groups. The age is constrained by 40Ar/39Ar analyses of associated volcaniclastics (V96.5 Ma), coupled with biostratigraphic correlation of the plant-bearing non-marine beds with marine units of the Krivorechenskaya Formation and the overlying Dugovskaya Formation. Limited palaeosol development and pronounced episodic floodplain aggradation indicate that the 100-m-thick plant-bearing volcaniclastic floodplain succession was deposited rapidly, resulting in excellent trapping and preservation of the plant communities, but dilution of the palynoflora. Analysis of the megaflora (s 100 foliage taxa, plus woods and fructifications) provides a ‘snapshot ’ of the mid-Cretaceous climate, and offers reliable quantitative climatic signals of conditions near the mid-Cretaceous North Pole. Multivariate analysis of leaf physiognomy (Climate Leaf Analysis Multivariate Program) on the whole flora suggests that the plants experienced a mean annual temperature of 13.0> 1.8‡C and a cold month mean temperature of 5.5> 3.3‡C. However, analyses of individual florules yield slightly different results that help