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Palynology
Fredrick J. Rich and Gordon D. Wood

Researchers in the field of palynology, the study of pollen, fall into one of two general camps of {emdash} those using palynology as an exploration tool in the search for hydrocarbons, and those who use it for archaeological, paleoclimatic, forensic or related problems. American Association of Stratigraphic Palynologists (AASP) President Sharma Gaponoff described the evolution of biostratigraphy programs among major oil companies in the United States in the December 2003 AASP Newsletter. Emphasis in palynology in the United States, however, is shifting away from that decades-old application of the science, and into other areas.

At the last AASP annual meeting (held jointly with the Canadian Association of Palynologists and the North American Micropaleontological Section of SEPM in St. Catharines, Ontario), the keynote speaker was Jim Dickson, known for his work with Ötzi, the Alpine "Iceman" (Scientific American, May 2003; Geotimes, February 2004). That archeological spin continued with the Best Student Paper Award being presented to Matthew Peros of University of Toronto, whose presentation was entitled "Micropaleontological Research in North Central Cuba: Implications for Prehistoric Archeology." Using the pollen/plant record, Peros determined that, beginning about 1500 years before present, the native inhabitants of Laguna de la Leche apparently lived in a coastal settlement which is now land-locked.

The archaeological application of palynology is not new, but its growing visibility illustrates changing emphasis within the science. The Eleventh International Palynological Congress (Granada, July 4-9, 2004) will feature traditional topics in Paleozoic, Mesozoic and Cenozoic palynology, but sessions will include entomopalynology, melissopalynology, forensic palynology and pollen databases. The inquisitive palynologist must embrace these changes in needs and interests as opportuntunities for new direction.

Recent palynological research has focused on climate volatility, whether related to the thawing of Ötzi or ancient planktonic flora. Several papers have used dinoflagellate cysts and other organic-walled microphytoplankton as proxies for reconstruction of paleoproductivity, interpretation of climatic trends and identification of paleobiological provinces.

Francine McCarthy and colleagues (Review of Palaeobotany and Palynology, 2004, v. 128, no. 1-2, p. 81-95) studied the Late Pliocene-Recent palynological and terrigenous influx to the abyssal Atlantic and Pacific. They suggest that sequestration of organic and inorganic carbon had been a factor in past greenhouse events.

F. Eynaud and co-workers (Review of Palaeobotany and Palynology, 2004, v. 128, no. 1-2, p. 55-79) used dinoflagellate cysts as proxies for North Atlantic surface circulation. Hydrological changes in the northern Atlantic Ocean reflect mechanisms of climatic change and are represented in palynological assemblages. Dinocysts, in conjunction with magnetic susceptibility, stable isotopes and planktonic foraminifera revealed climatic instabilities. Changes in the abundances of Spiniferites mirabilis and Operculidinium centrocarpum were particularly important; maximum abundances might reflect sea-surface temperature peaks.

Fabienne Marret and Karin Zonneveld (Review of Palaeobotany and Palynology, 2003, v. 125, no. 1-2, p. 1-200) published an atlas of global distributions of modern organic-walled dinoflagellate cysts. They synthesized distribution patterns and surface-water parameters (temperature, salinity, phosphate and nitrate concentrations), which will assist hydrological and climatologic comparisons with fossil material. This database can be accessed online.

Thomas Servais and colleagues (Palaeogeography, Palaeoclimatology, Palaeoecology 2003, v. 195, no. 1-2; p.1-228) developed preliminary paleobiogeographical models for Ordovician organic-walled acritarchs and prasinophytes. They identified Late Tremadocian evidence of a warm-water assemblage limited to low-latitude localities (Laurentia and North China). From the Late Tremadoc throughout most of the Arenig there is a peri-Gondwanan assemblage on the southern margin of Gondwana. This distribution corresponds almost exactly with that of the Calymenacean-Dalmanitaccean trilobite fauna. The acritarchs of Balticia are comparable to a temperate-water "province." Some representatives exhibit a fairly wide distribution; temperate water elements are recorded at about the same latitude in South China and Argentina. By the Arenig, maximum separation of continents had occurred, as reflected in pronounced biogeographical differentiation and distinct acritarch provincialism. Distribution of Ordovician organic-walled microphytoplankton appears similar to that of modern dinoflagellate resting cysts that are controlled by latitude and follow contours of the continental margins.

Bucefalo Palliani and Jim Riding (Palynology, 2003, v. 27) found potential linkages between paleoenvironmental changes, dinoflagellate speciation events and diversity peaks. They proposed that Early Jurassic transgressions probably increased the number of ecological niches in neritic (shallow water) habitats and might define successions related to Boreal and Tethyan bioevents. Although these two regions exhibit marked provincialism (influenced by sea-water temperature, coastal oceanic settings and paleosalinity), the transitional region between the two realms was diffuse and characterized by a mixed biota.

Finally, petroleum exploration themes still do run through palynology. Albert Holba and colleagues (Organic Geochemistry, 2003, v. 34, p.601) furthered the development of molecular "fingerprinting" of microscopic algal types to their geochemical building blocks and degradation products. An apparent link was identified between freshwater chlorococcalean algae and C30 tetracyclic polprenoids. This information can be employed to type source facies for oils, assisting in identifying hydrocarbon systems.

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Rich is professor of geology at Georgia Southern University, and is AASP's representative to the AGI Member Society Council. Wood is a consulting paleontologist with the irf group inc., and is located in Katy, Texas.

Links:
Atlas of global distributions of modern organic-walled dinoflagellate cysts


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