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Steven A. Jennings
The pollen from five packrat middens from the White Mountains region of California were analyzed and compared to previously analyzed macrofossils from the same middens. The middens span the time from ca. 20,000 yr BP to the middle Holocene. While there are similarities in the pollen and macrofossil data, there are some subtle differences between the two types of data. The pollen data would support the macrofossil evidence that indicates the arrival of Pinus by the early Holocene. In spite of this general agreement, the pollen evidence suggests that Pinus was not common in the vicinity of the early Holocene midden sites. The results of this study would indicate the importance of using both the macrofossils and pollen evidence from packrat middens.
Sofie Lindström
Ninety-one samples from three sections at Fossilryggen in the Vestfjella mountain range of Antarctica have been investigated palynologically. Sixty-six taxa are recognized in forty-eight productive samples from two of these sections: the southern section at Fossilryggen and the NW Nunatak section. The palynomorphs have been subjected to contact metamorphosis and display various grades of thermal maturity, ranging in color from light brown to black. They also display various degrees of preservation. Among the spores found are Didecitriletes ericianus, D. uncinatus, Dictyotriletes labyrinthicus, (Anderson) comb. nov., Horriditriletes filiformis, Microbaculispora trisina, M. villosa, Osmundacidites wellmanii and Gondisporites raniganjensis. Taeniate and non-taeniate bisaccates are dominant and include Scheuringipollenites ovatus, S. maximus, Vitreisporites pallidus, Protohaploxypinus spp., Striatopodocarpidites spp. and Guttulapollenites hannonicus. Other pollen-grains present are Weylandites lucifer, Praecolpates sinuosus and Bascanisporites undosus. Althought the sections have been interpreted as being deposited in a near-shore marine environment, acritarchs and algae are rare in these assemblages and include the forms Peltacystia venosa, P. monile, Cymatiosphaera gondwanensis, Leiosphaeridia sp. B and Brazilea scissa.
These assemblages are regarded as being of Late Permian age, Kazanian to Tatarian, and are correlated with Upper Stage 5 palynofloras in Australia, and with similar assemblages in Africa and India. Correlations are also made with other Late Permian palynofloras within Antarctica.
Dennis Burger
This paper discusses the results of a palynological examination of thirty-three dredge samples from sediments exposed on the sea floor, offshore Western Australia. The samples are dated as latest Triassic to Early Cretaceous, and represent marine to coastal nonmarine environments. They are integrated with the geological framework of the Rowley Terrace, Wombat and Exmouth plateaus, and Carnarvon Terrace, on the basis of palynological evidence derived from regional petroleum exploration wells and deep sea (ODP) drilling. Biostratigraphic affinity of the dredge samples is given in terms of zonal schemes for spores, pollen grains, and dinoflagellate cysts, currently in use for the Mesozoic of the Australian region. The ages of certain zonations are reviewed on the basis of fresh evidence from ammonites, conodonts, ostracodes, foraminifera, and nannofossils. Details are given of the distribution of species, and several species are described and discussed. New spore-pollen species Clavifera deformans and Cycadopites dejersey, and a possible algal species, Bartenia helbyi, are proposed.
E. G. Ottone
A diverse and relatively well-preserved palynological assemblage has been recovered from the Los Monos Formation in the Quebrada Galarza well, northwestern Argentina. Ninety-eight species of palynomorphs are represented. Thirty-four are miospores (with two dubiously placed), fifty-one are acritarchs, eight are chitinozoans and five are scolecodonts. Two new genera of acritarchs, Crucidia and Hemiruptia, are proposed herein. Seven new species are described: one spore, Acinosporites ledundae; four acritarchs, Ammonidium garrasinoi, Cymatiosphaera apiaria, Hemiruptia legaultii and Polygonium barredae; and two chitinozoans, Angochitina galarzae and Belonechitina holfeltzii. Previously described species of palynomorphs suggest a late Givetian-early Frasnian age for the Los Monos Formation in the Quebrada Galarza well.
Stratigraphic and phytogeographic implications of the palynological assemblage are discussed. The presence of several terrestrial species previously recognized in northern Gondwana and in the Northern Hemisphere reinforces currently accepted paleogeographical reconstructions of the upper Middle through lower Upper Devonian. Acritarch data corroborate the existence of important phytoplanktonic links between Gondwana and the Northern Hemisphere via a relatively temperate marine realm.
Raffaella Bucefalo Palliani, James B. Riding and Stefano Torricelli
The acritarch Polygonium jurassicum sp. nov. is proposed for polygonomorph acritarchs with a surface ornament of hollow spines. It is the second species of Polygonium described from Jurassic sediments. Polygonium jurassicum sp. nov. is reported from lower Toarcian sediments from central Italy and northwest Greece; the stratigraphic range is compared with the ammonite and calcareous nannofossil zonations.
Axel Munnecke and Thomas Servais
Scanning electron microscopy of polished, slightly etched rock surfaces provides excellent observation conditions for palynomorphs. In the present study, samples from micritic limestone-marl alternations in the Silurian of Gotland, Sweden, and from Pliocene limestones of the Bahamas are used.
The Silurian limestones contain three-dimensionally preserved acritarchs, chitinozoans, and prasinophytes, allowing the study of the outer and inner wall surfaces. In contrast, siltstones and marls provide slightly to strongly deformed, partly damaged specimens, which become completely flattened and crushed when the sediment is highly compacted.
The observation of palynomorphs in polished surfaces can be considered as a complementary method to the standard preparation technique of hydrofluoric and hydrochloric digestion of rock samples, where it is possible that parts of the palynological spectrum may be lost during heavy-liquid separation, filtering, centrifugation, or bleaching procedures. The detailed observation of the polished rock surface covers the complete spectrum of organic-walled microfossils, including very small specimens (smaller than 10 µm). In addition, the method allows a view on the palynomorphs within the sediment (in situ) and provides information on the compaction and diagenetic alteration.
Gordon D. Wood
Beromia rexroadii gen. emend. et sp. nov. (algae incertae sedis) is described and illustrated from the Red Mountain Formation of Alabama and Georgia, the Lulbegrud Shale Member of the Noland Formation (Crab Orchard Group) of Kentucky, and the Lower Sodus Shale of New York. The wide geographic distribution and apparent short stratigraphic range of this new acritarch suggests it may be significant index fossil for correlation of Upper Llandovery strata of the eastern North American Platform. B. rexroadii gen. emend. et sp. nov. occurs with a diverse and abundant acritarch assemblage suggesting deposition in normal marine, nearshore to open-shelf environments.
The genus Beromia is emended here to incorporate morphologies having more than three processes and a new type of combination excystment structure. This new structure has an epityche on the epiderm, here termed an endodermal epityche. The periderm, in contrast, has a simple lateral split immediately adjacent to the endodermal epityche.
John J. Skvarla, John R. Rowley and William F. Chissoe
Representative types of exine corrosion, seen on scanning electron micrographs, are illustrated from a leaf mold sample from the corrosion experiment of Havinga (1964). This work complements earlier transmission electron microscopy of the same sample (Rowley et al., 1990). Corroded areas are among the most dramatic indicators and products of exine destruction in samples of pollen and spores from Havinga's leaf mold material. Severely corroded regions, as seen using the secondary emission mode of the SEM, were most often found on exines with a continuous tectum (Myrica, Betulaceae, Corylaceae, Ulmus), but they also occurred to some degree in Fagus and on spores of Lycopodium. In taxa having pollen with a more or less continuous tectum the surface of the tectum was not destroyed but instead became depressed to the level of the floor of corroded areas. This "sunken tectum" aspect of corrosion results from tunneling within the tectum without destruction of the surface. Muri of reticulated exines showed little indication of corrosion. Muri of Lycopodium, considered by Havinga as the most resistant exine in his experiment, were, however, often seen to be somewhat corroded and in some spores severely so. Fractures or tears, common to exines of many of the 19 taxa in Havinga's material, are illustrated for Fraxinus, Fagus, Quercus, Tilia, Pinus, and Lycopodium. Isolated sectors fractured from some taxa, e.g., Pinus and Tilia, are identifiable, but others are difficult to identify. In Pinus, where a portion of a sacculus was broken off, the surface of the foot layer showed hemispheroidal unit-structures. Examples of folding and collapse were especially prominent in Taxus, Juniperus, Salix and Acer. Exines of these taxa were extremely difficult to recognize as pollen grain exines under oil immersion or with moderate SEM magnifications, although at higher magnifications exine structural details were seen to be intact. Small pit-like circular holes were frequent on exines of Myrica and other betuloid grains, Fagus, Acer, Polypodium, and Lycopodium. These small holes may be of special interest since in Lycopodium they have been reported following abiological experiments.
John H. Wrenn
Specimens of Pseudorhombodinium lisbonense gen. et sp. nov., the type species of the new fossil dinoflagellate genus Pseudorhombodinium gen. nov., were recovered from an outcrop of the lower part of the Lisbon Formation (middle Eocene) in Little Stave Creek, Clarke County, Alabama. The sample containing P. lisbonense gen. et sp. nov. is a calcareous glauconitic sand bed located approximately 104 ft above the Jackson Fault, the reference datum for the base of the Paleogene section exposed in Little Stave Creek.
Whether Pseudorhombodinium gen. nov. is a dinoflagellate cyst (dinocyst) or the remains of a thecate, motile dinoflagellate is uncertain. However, for convenience it will be treated as a dinocyst in this paper.
Pseudorhombodinium is established to accommodate organic-walled, subrhombic to subpentagonal shaped, circumcavate dinocysts with a hexa paratabulation style and 2a intercalary archeopyle, Type Ia/Ia. The periarcheopyle is iso-deltaform, the endoarcheopyle is eury-deltaform, and the operculum of each is adcingularly adnate. In addition to its shape and unusual archeopyle, P. lisbonense is characterized by its large size, complex flagellar pore structure, an incised paracingulum and parasulcus, the absence of lateral horns and by the presence of closely spaced, very diminutive antapical horns.
Associated dinocysts, foraminifers and calcareous nannofossils indicate that the sample containing P. lisbonense is early middle Eocene in age. The depositional paleoenvironment was characterized by water temperatures close to those of the modern northern Gulf of Mexico (mean annual surface temperature is approximately 26°C/77°F), a hard sandy bottom and water depths of less then 50 m (164 ft). No specimens of P. lisbonense were observed in 87 other samples studied from the Little Stave Creek section (middle Eocene-late Oligocene).
Gary A. Olmstead, William C. Cornell and Gerald L. Waanders
Upper Jurassic strata exposed within the northeastern Chiricahua Mountains, southeastern Arizona, contain a transitional to open marine facies consisting of supratidal sediments, intrabasinal turbidites, pelagic sediments, and submarine volcaniclastics. This sequence is underlain unconformably by the Permian Concha Limestone and is thrust to the southwest over the Cretaceous Bisbee Group. These marine strata were deposited during a period of active rifting accompanied by a northwest transgressive incursion into a half-graben depositional depression known as the Bisbee Basin. Progressive infilling of Cretaceous Bisbee Group sediments resulted in a succession of Upper Mesozoic strata that is unique to this region of the southwestern cordillera.
Fifteen genera and thirteen species of dinoflagellate cysts date this sequence from middle Oxfordian to early Kimmeridgian. Ammonites Idoceras striatum (Imlay), Perisphinctes ("Disco-sphintes"), and Dichotomosphinctes cf. D. wartae (Bukowski) substantiate this age, as well as questionably establishing the Oxfordian-Kimmeridgian boundary within this section.
The presence of dinoflagellate cysts, in conjunction with Tethyan ammonites, indicates a time of normal-open marine conditions within this region and documents the northernmost incursion of the Tethyan Seaway into this region of southeastern Arizona.