John H. Wrenn

Maceral, Total Organic Carbon, and Palynological Analyses of Ross Ice Shelf Project Site J9 Cores

Analyses of macerals and total organic carbon indicate that the low organic content of core sediments from Ross Ice Shelf Project site J9 has been selectively reduced further, probably by postdepositional submarine oxidation. Palynological analysis revealed a reworked Paleogene dinocyst flora of low diversity (the transantarctic flora). This constitutes the most southerly dinocyst flora reported thus far. The antarctic distribution of the transantarctic flora supports the existence of a transantarctic strait during the Paleogene. The J9 sporomorph assemblage also is reworked and Paleogene in age.

Integrated taphonomy of an avian death assemblage in marine sediments from the late Pliocene of Florida

We integrate taphonomic data on vertebrate and invertebrate paleontology, micropaleontology and palynology to explain the formation of a late Pliocene death assemblage of marine birds and fish in the “Pinecrest Sand”, Gulf Coastal Florida. Stereonet plots of orientation data on over 1500 cormorant (Phalacrocoracidae: Phalacrocorax) bones indicate that this fossil assemblage formed first from gradual accumulation of bone, shell and sediments on a barrier island beach, and second by rapid sedimentation in a quiet, back-beach setting associated with multiple episodes of breaching of the barrier. This latter event resulted in the preservation of 137 partial and complete cormorant skeletons and thousands of isolated bones that show a high angle of dip and a preferred orientation to the northeast. Invertebrate fossils exhibit taphonomic signatures characteristic of high-energy reworking with a large percentage of abraded shell fragments similar to beach deposits. Moreover, these data indicate that more than a single depositional episode caused the formation of the deposits referred to as the bird layers. Palynological evidence supports this conclusion. The pollen recovered from the deposits is highly abraded and broken and does not represent an in situ vegetational environment as compared to other deposits of this age in Florida and Georgia. The large number of cormorant and other seabird and fish remains in the bird layers appears to have been caused by a series of toxic red tides that occurred on the Gulf Coast of Florida. These events today cause die offs of large flocks of cormorants and bottom-dwelling fish similar to those recovered from the site. Palynological analysis of the sediments revealed abundant cysts of a dinoflagellate species known to produce toxic red tides. The most likely cause of the death of the cormorants and other vertebrates at this site is a toxic bloom of a variety of Pyrodinium bahamense, the thecate form of the dinoflagellate cyst Polysphaeridium zoharyi, which has a stratigraphic range from the lower Eocene to the Holocene.

Restudy of the holotype of Operculodinium centrocarpum (Deflandre & Cookson) wall (Dinophyceae) from the Miocene of Australia, and the taxonomy of related species

Abstract Operculodinium centrocarpum (Deflandre & Cookson) Wall 1967 is one of the most commonly reported dinoflagellate cysts (dinocysts) in samples from Tertiary and Quaternary deposits. However, at least two distinct dinocyst morphologies are assigned to this species in the literature at the present time. In addition, two separate species have been erected for one of these distinct morphologies. In order to define criteria with which to differentiate these morphologies, holotype and topotype material of O. centrocarpum (Deflandre & Cookson) Wall 1967 and O. echigoense Matsuoka 1983 were restudied and compared with dinocysts of Protoceratium reticulation (Claparede & Lachmann) Butschli 1885. Re‐investigation of the holotype and topotype specimens of O. centrocarpum (Deflandre & Cookson) Wall 1967 (=Hystrichosphaeridium centrocarpum Deflandre & Cookson 1955) and O. echigoense Matsuoka 1983 demonstrated that O. echigoense Matsuoka 1983 is a junior synonym of the former. This restudy also confirmed that O....

New species of dinoflagellate cysts from the Bou Regreg Core: A Miocene-Pliocene boundary section on the Atlantic Coast of Morocco

The Bou Regreg borehole section is situated a few kilometers north of Rabat, in northwestern Morocco, at the western end of the Rifian Corridor. The Bou Regreg core penetrates 185 m of Late Miocene to Pliocene marls (chrones 7 to Gilbert). Palynological study of 180 samples from the core revealed extremely abundant and diverse dinocyst assemblages. In contrast, spore and pollen assemblages were sparse. The purpose of this paper is to document one new genus and seven new species of dinocysts, including: Capisocysta wallii Warny et Wrenn, gen. et sp. nov., Hystrichosphaeropsis somphosa Warny et Wrenn, sp. nov., Impletospheridum acropora Warny et Wrenn, sp. nov., Operculodinium floridium Warny et Wrenn, sp. nov., O. oriensum sp. nov., Spiniferites falcipedius Warny et Wrenn, sp. nov. and Barssidinium olymposa Warny et Wrenn, sp. nov. The occurrence of some of these taxa in correlative sections (in the Gulf of Mexico, in the Caribbean Sea etc.) suggest that they are biostratigraphically useful for correlation (Warny and Wrenn, 1996).

PALYNOLOGY OF THE NBP03-01A TRANSECT IN THE NORTHERN BASIN, WESTERN ROSS SEA, ANTARCTICA: A LATE PLIOCENE RECORD

Abstract Fifty-seven samples taken from ten piston cores collected along a transect off the continental margin of the Northern Basin, Ross Sea, Antarctica were analyzed for palynomorphs. Moderately diverse assemblages of marine microplankton and terrestrial palynomorphs were recovered. The palynomorph assemblages have been subdivided into two main groups: the in-situ flora (including acritarchs, dinoflagellate cysts, leiospheres and prasinophyte algae mainly composed of cymatiosphaerids), and the reworked flora (including dinoflagellate cysts, pollen and spores). The leiospheres are the most abundant palynomorphs. This prominence in the relative abundance of leiospheres has been reported as typical of assemblages found today at the limit between seasonal and pack ice in the Arctic. In-situ dinoflagellate cysts are sparse. They are mainly represented by Lejeunecysta, which, based on species similarities to those from Cape Roberts, are believed to be of Oligocene to Pliocene age. All other dinoflagellate cysts recovered are the result of reworking from Eocene to Oligocene sediments. Reworked spores and pollen comprise the second most abundant group. They are of moderate diversity and include an Eocene or older assemblage of Nothofagidites, Podocarpaceae and Proteaceae. Other taxa are representative of warmer rainforest vegetation, with Oligocene and Neogene taxa that include representatives of woodland to herbaceous/low shrubby tundra vegetation growing in colder subpolar climates. These assemblages indicate either different periods of deposition or reworking from diverse sources. Through seismic correlation and diatom analysis, the sediments are believed to be Late Pliocene in age. On this basis, it is postulated that the major glacial advance, RSU 2 of Brancolini et al. (1995) or Unconformity 10 (U10) of Bart et al. (2000), occurred before 2.3 Ma, which is the oldest age of in-situ species recovered in units above U10. As both terrestrial and marine reworked taxa include assemblages of Eocene to Oligocene age, it is assumed that those reworked components were yielded from a single source; most probably Eocene to Oligocene shallow marine strata eroded and transported from the area of Ross Island to the shelf margin through ice streams located in the Drygalsky and Joides basins.

Middle Wisconsinan and recent wet site mummified wood, humus, peat, and pollen, Santa Rosa Island, Florida

Abstract Macrobotanical samples obtained from submerged, previously buried, tree stumps in growth position and peat and humus/humate layers from the surf zone of Santa Rosa Island were identified and dated by 14C analysis. Dates obtained clustered in two time spans, 45 440 yr BP. These subfossil macrobotanicals are well preserved in spite of submergence. Conifers of the family Cupressaceae (cf. Juniperus virginiana) and Pinaceae and a dicotyledon of the family Lauraceae (cf. Persea) are the principal tree species identified. Presence of these species in the current surf zone in conjunction with modern vegetation distribution indicates sea level was lower during the Middle Wisconsin and Late Holocene. Microbial decay patterns in a Pleistocene wood sample suggest basidiomycete infestation by brown-rot fungi prior to burial and successional decay by actinomycete bacteria during its waterlogged state. Extensive destruction of S2 microfibrils of the secondary cell wall that left a residual skeleton of lignin and presence of pyrite framboids in Pleistocene wood inform on its depositional history. Pollen/spore assemblages from Holocene humus/humate suggest a former maritime forest habitat with back-barrier freshwater basins. Macrobotanical identification, radiocarbon dates, and palynological indicators suggest Santa Rosa Island is an unstable barrier island at a critical point of degradation due to marine intrusion coincident with global sea-level rise, storm overwash burial of existing maritime plant communities, and accelerated erosion of former vegetational foci by sand aggradation. The 14C date and location of stump sub-samples SRI 1b and SRI 1f in conjunction with previously reported regional 14C dates indicate that SRI 1 occupied a topographic high during marine oxygen isotope chronozone (OIC) 3 rather than being near sea level. Holocene samples spanning the last two millennia verify the occurrence of maritime forest and high dune habitat taxa in the present surf zone.

COASTAL DYNAMICS AND CULTURAL OCCUPATIONS ON CHOCTAWHATCHEE BAY, FLORIDA, U.S.A.

Abstract A multidisciplinary project on an archaeological site on the Mitchell River, which feeds into Choctawhatchee Bay on the Florida panhandle, was designed to understand human adaptations to a dynamic hydrological environment during the Middle and Late Archaic period (ca. 8000–3000 B.P.). Now in a freshwater environment, on a sandy terrace above the Mitchell River floodplain, the Mitchell River 1 archaeological site contains an oyster-shell midden and other features indicating human exploitation of an estuarine environment. Estuarine exploitation at the site occurred over a long span of time, from around 7300 to 3400 2cal B.P., although the site was abandoned two or three times over the millennia. The site was more permanently abandoned after 3400 B.P. Because estuarine shellfish, such as oysters, are low trophic level species, they have been considered marginal resources, and archaeologists modeling collector strategies assume that people will not travel far to obtain them. Under an optimal foraging model, estuarine resources should have been closer to the site than at present. A multidisciplinary team was assembled to address whether a mid-Holocene sea-level highstand had produced estuarine conditions in the Mitchell River floodplain during the Archaic. Using microfossils and stratigraphy from a dated core taken in the floodplain due south of the site, the project members attempted to correlate the changing paleoenvironment with human occupation and abandonment of the area. Results indicate that, at ca. 7300 cal B.P., when the Mitchell River 1 site was first inhabited, the floodplain was a shallow, open, sedge marsh. The site inhabitants must have traveled some distance to gather the oysters and other estuarine species that were discarded on the site. The earliest occupation was brief, but the site was reoccupied between 5900 and 5300 cal B.P., when the floodplain had become a Taxodium/Nyssa swamp. Site deposits indicate intensive exploitation of oyster and to a lesser extent Rangia, which may have been closer to the site than at 7300 B.P. but still would have required some travel. At some point, the mouth of the Mitchell River was forced eastward, and the bayhead delta, recognized as a 2-meter-deep wedge of sand in the core, was located adjacent to the site. By 4700 cal B.P., brackish water conditions prevailed, although direct evidence of oyster beds in the immediate area is lacking. Unfortunately, scouring of the core sediments sometime after 4700 cal B.P. destroyed the paleoenvironmental record for the last part of the Archaic occupation of the site. However, some evidence in Core 1, along with research elsewhere on the Florida panhandle, suggests that catastrophic storms may have played a part in the more permanent abandonment of the site after 3400 B.P.

Palynomorph distribution in modern tropical deltaic and shelf sediments– mahakam delta, Borneo, Indonesia

Abstract The Mahakam Delta is a tropical, fluvio—tidally dominated delta prograding onto a mixed siliciclastic—carbonate shelf. Surface sediments were collected from 12 distinctive depositional environments extending from the head of the Mahakam Delta to the shelf edge. Organic matter was extracted from 200 samples by acid digestion, and seven palynomorph types (pollen, embryophyte spores, fungal spores, foraminiferal linings, copepod eggs, tintinnomorphs, and dinocysts) were identified and counted, and their percentages and concentrations calculated. Total organic carbon (TOC), lithology, and depositional environments were recorded for each sediment sample. The amounts of terrestrial palynomorphs in sediments can be explained by transport and depositional processes, and four groups of environments are identified (tidally influenced, detrital peat beach, lowland rain forest, and marine shelf). Because of tidal flushing of the delta plain, pollen, embryophyte spores, fungal spores and soft plant debris from the soil litter are deposited together with clastic mud at slack-water periods. As a result, all tidally-influenced environments exhibit constant numbers of pollen, embryophyte spores, and fungal spores per unit of TOC. In lowland rain forest sediments, there is minor clastic dilution and the numbers of pollen and spores are three to 10 times higher per unit TOC than in tidally-influenced sediments. In detrital peat beach and marine shelf sediments, the number of sporomorphs per unit TOC is lower than expected because of the selective removal of sporomorph-sized particles by wave action and of dilution with autochthonous marine organic matter respectively. In contrast, the amounts of marine palynomorphs in sediments are related to the depositional environments. Relative amounts of marine palynomorphs increase gradually offshore, as both the sporomorph percentages and concentrations decrease simultaneously. Once in fully marine conditions, concentrations of marine palynomorphs are comparable in all shelf environments. The marine assemblages are mainly represented by Zooplankton (copepod eggs) and benthic protists (foraminiferal linings), the phytoplanktonic constituent (dinocyst) playing a subordinate role.

Pseudorhombodinium lisbonense gen. et sp. nov., a new dinoflagellate fossil from the Lisbon formation (middle Eocene), Little Stave Creek, Alabama

Abstract 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 o...