CLUSTER AND ORDINATION ANALYSES, EXPLORATORY TOOLS IN PROVENANCE AND TAPHONOMY STUDIES: A CASE STUDY USING THE BISSEKTY FORMATION IN THE KYZYLKUM DESERT OF UZBEKISTAN

The goal of many provenance and taphonomic studies is to determine the origin of clastic rocks or fossil assemblages by assessing the effects of physical sedimentary processes in different facies on sedimentary particles. Cluster and ordination analyses facilitate this goal by identifying spatial and temporal patterns among assemblages. This study uses these multivariate analyses to aid in reconstructing the taphonomy, paleoecology, and identifying a source for the faunal assemblage of the Late Cretaceous (90 m.y.) Bissekty Formation on the Dzharakuduk escarpment in the Kyzylkum Desert of Uzbekistan. The Bissekty Formation is 80 m thick, dominated by poorly-lithified, cross-bedded fluvial sandstone, with 4-8 laterally extensive, clast-supported, iron-oxidized intraformational conglomerates (IFCs). Cluster and ordination analyses were used to determine similarities among the IFCs based on their absolute taxonomic abundance and presence/absence of taxa. To determine the primary factor(s) driving the cluster patterns: taxonomic abundance, richness, environmental-restrictions (marine, brackish, freshwater, aquatic, semi-aquatic, and terrestrial), and size were examined. Relative Sorenson, Sorenson, and correlation distance measurements were used in the study, results were consistent across methodologies. Cluster and ordination patterns were driven by the aquatic taxa, which were dominated in abundance and richness by marine or brackish-tolerant taxa. By mapping the abundance of terrestrial, semi-aquatic, and aquatic taxa of individual IFCs onto ordination space, the relative position of the coastline with reference to the Dzharakuduk escarpment can be inferred during the deposition of the Bissekty and the source identified for the marine and brackish tolerant taxa of the taphonomically-transported local Bissekty faunal assemblage. The Bissekty represents an aggradational ‘lowstand' system and the IFCs represent flooding surfaces that resulted from regional changes in the depositional regime after a drop in eustatic sea-level. The local Bissekty fauna represents lowland floodplain, coastal communities. During the Turonian, Middle Asia was a warm semi-humid environment, making the local Bissekty fauna a better paleogeographic comparison to the Upper Cretaceous of western North America than the more arid settings of Mongolia and China.