. Bulletins of American paleontology. Pollen Zonation: O'Neal et al. 115 Environment Mangrove Swamp Freshwater Marsh Headwater Marsh Brackish Marsh Upland Cluster. Text-figure 4.—Dendrogram illustrating association of surface sample cluster groups to environments. Ten clusters are designated based on a Chi-squared distance of ~2 (dashed line). mocks and freshwater marsh with cypress hammocks vegetation communities, while those in cluster 5 are mainly from the freshwater marsh slough vegetation community. The dominant pollen types associated with freshwater marshes are chenopods. triporates. Ny
. Bulletins of American paleontology. Pollen Zonation: O'Neal et al. 115 Environment Mangrove Swamp Freshwater Marsh Headwater Marsh Brackish Marsh Upland Cluster. Text-figure 4.—Dendrogram illustrating association of surface sample cluster groups to environments. Ten clusters are designated based on a Chi-squared distance of ~2 (dashed line). mocks and freshwater marsh with cypress hammocks vegetation communities, while those in cluster 5 are mainly from the freshwater marsh slough vegetation community. The dominant pollen types associated with freshwater marshes are chenopods. triporates. Nym- phaeci, Sagittaria. cf. Ovoidites, Compositae, and Cy- peraceae (sedge family). Both of these clusters contain a wide variety of freshwater-dependent species, but chenopod abundances are approximately 33% higher in cluster 5 (Table 1). Samples from clusters 6 and 7 are from sites located near the transition between the Everglades Depression and the mangrove swamp (Text-fig. 1). Although this area is designated as part of the brackish marsh veg- etation community by Riegel (1965) (Text-fig. 2), Rie- gel (1965) also describes this area as a unique zone called the headwater marsh. The assignment of head- water marsh will be used to designate this area in this study as well. Cluster 6 is comprised of samples 64- 33. SR-25. SR-26. SR-28. and SR-29. whereas cluster 7 is comprised of samples 62-24. SR-17 to SR-24, and SR-30. Samples in cluster 6 were obtained from lo- cations along the margin between the freshwater marshes and brackish marsh, while samples in cluster 7 were selected from a more seaward position within the brackish marsh vegetation community (Text-fig. 2). The dominant pollen types associated with the head- water marsh are Rhizophora, chenopods. triporates, Conocarpus, and Osmunda (ferns). Cluster 6 samples have more than twice the average frequency of che- nopods of cluster 7. whereas cluster 7 samples display a marked increase in Rliizophora and triporates (Tabl
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