NEW ARTICLE PUBLISHED ONLINE!
Lycopsid megaspores from the Upper Triassic of Svalbard and their relationship to the floras
and palaeoenvironments of northern Pangaea
Niall W. Paterson, Peter H. Morris & Gunn Mangerud
Abstract: Triassic megaspore assemblages from Svalbard, Arctic Norway, are described for the first time based on the analysis of the Upper Triassic (Carnian–Norian/Rhaetian) Kapp Toscana Group on the island of Hopen. Two megaspore zones are described: the late Carnian ‘Dijkstraisporites beutleri Zone’ (undifferentiated De Geerdalen Formation), and the Norian/Rhaetian ‘D. beutleri – Verrutriletes preutilis Zone’ (Svenskøya Formation). The megaspores are attributed to heterosporous lycopsids, and likely correspond to the microspore Aratrisporites, which was observed in palynological preparations. Megaspore occurrence was highest in delta-plain and associated with lake-mire deposits. However, their co-occurrence with marine microfossils suggests episodic marine influence, and is consistent with previous interpretations of Triassic lycopsids as coastal plants, with a palaeoecological preference for brackish mangrove-type or marginal deltaic environments. The absence of megaspores in the overlying Hopen Member and Flatsalen Formation is likely related to a marine transgression during the early Norian, as indicated by previous studies, and by the recovery of low diversity assemblages of agglutinated foraminifera. The transition to ostracod-dominated microfaunas in the middle part of the formation is consistent with a regionally extensive maximum flooding surface, prior to a return to megaspore-dominated assemblages in the fluvio-deltaic deposits of the Svenskøya Formation. Despite the abundance of their mega- and microspores, lycopsid fossils are almost entirely absent within palaeobotanical collections from the island, which we ascribe to their herbaceous habit and consequent low preservation potential. The results of this study show lycopsids to be an important component of the local ecosystem and thus contribute to a more complete understanding of the Late Triassic floras of the northern Pangaean coast.
Papers in Palaeontology (2019)
https://doi.org/10.5061/dryad.1mn51s6
NEW ARTICLE PUBLISHED!
Palynology vs. model simulation: oceanographic reconstruction of incomplete data from the
Cretaceous Greenland–Norwegian Seaway
Wiesława Radmacher, Igor Niezgodzki, JarosławTyszka, Gunn Mangerud and Martin A. Pearce
Abstract. Dinoflagellate cyst-based analyses of the upper Albian to upper Maastrichtian successions in the Greenland–Norwegian Seaway (GNS), cores 6711/4-U-1 and 6707/10-1, show significant changes in assemblage composition. Palaeoenvironmental reconstructions from the early Late Cretaceous are in general agreement with actual reconstructions indicating the highest eustatic sea-level and warmest sea surface temperatures near the Cenomanian–Turonian transition, with sea-level regression and cooling towards the end of the Cretaceous. The study of an incomplete Maastrichtian interval indicates short warming episodes that were superimposed on the global long-term cooling trend during the Late Cretaceous. The presence of Maastrichtian dinoflagellate cysts indicative of oceanic conditions reflects coeval deepening of the GNS. The region was also influenced by pre-rifting processes, resulting in palaeogeographical reconfigurations. Comparable late Campanian dinoflagellate cyst assemblages from the Western Interior and Greenland–Norwegian seaways suggest a marine connection between these regions despite an enhanced global marine regression during the Late Cretaceous. To better understand our palynological signal we use numerical climate model simulations examining the local current regime for the latest Cretaceous (winter and summer seasons) assuming an atmospheric carbon dioxide level of 4x pre-industrial (1120 ppm) and applying various palaeogeographical reconfigurations: 1) Western Interior Seaway (WIS) and Hudson Seaway (HUD) closed; 2) WIS opened and HUD closed; 3) WIS and HUD opened. The results demonstrate that GNS currents are dominated by warmer water-masses from the southwest during times when the GNS and WIS are connected. In addition, HUD surface currents show a tendency to drive WIS water eastward, i.e. towards GNS that most likely facilitated biogeographic species exchange. These findings support the palynological data suggesting that the WIS and GNS could have been connected through the HUD at least during the late Campanian. In this case, the seaway must have played a significant role in the exchange of water-masses and heat transport. Further restrictions between the Arctic Basin and the global ocean influenced by lowering sea- and salinity-levels could consequently be an important factor contributing to the latest Mesozoic global cooling.
Newsletters on Stratigraphy, 53/1, 93-120, 2020
https://doi.org/10.1127/nos/2019/0527
NEW ARTICLE PUBLISHED ONLINE!
A dinoflagellate cyst zonation of the Cenomanian and Turonian (Upper Cretaceous) in the Western Interior, United States
Paul Dodsworth and James Eldrett
Abstract. This study documents the detailed palynology of the Bridge Creek Member, Greenhorn Limestone Formation, at the Rock Canyon anticline outcrop, west of Pueblo, Colorado, USA. The section is the formally ratified Global Boundary Stratotype Section and Point (GSSP) for the base of Turonian Stage and corresponding Lower Turonian Substage, and the only proposed GSSP for the base of the Middle Turonian Substage. The authors’ previously published palynological data from the underlying Cenomanian strata in the nearby US Geological Survey (USGS) Portland-1 core, and from cores and an outcrop of Cenomanian, Turonian and earliest Coniacian age in SW Texas, are reviewed for biostratigraphy. Dinoflagellate cyst ranges and events in both areas are calibrated against other published bio- and chemostratigraphical (carbon isotope) data and an astronomical age model. A regional dinoflagellate cyst zonation is proposed, adapted from a Central and Northern European scheme, comprising three zones and four subzones. Comparison with vintage published palynological data from other states, including Arizona, Kansas, Utah, Wyoming and Montana, indicates that the zonation is probably applicable to marine sections throughout the Cretaceous Western Interior Seaway of the USA. The new palynological data from around the Lower–Middle Turonian boundary at Pueblo support its proposal as a GSSP.
PALYNOLOGY, online 2019
https://doi.org/10.1080/01916122.2018.1477851
NEW ARTICLE PUBLISHED!
A new marine palynomorph from the Turonian (Upper Cretaceous) in the USA
Paul Dodsworth and James Eldrett
Abstract. This paper documents a previously undescribed marine palynomorph, Doricodinium obscurum gen. et sp. nov., from Upper Cretaceous sections in the central and southern Western Interior of the USA. Although an archaeopyle has not been confirmed, a case is made here for a probable dinoflagellate cyst, possible peridinioid affinity. The type locality of D. obscurum is the Global boundary Stratotype Section and Point (GSSP) for the base of Turonian Stage, at Pueblo, Colorado, where it consistently occurs in intra-Lower to middle Turonian deposits. The taxon also occurs consistently in intra-Lower Turonian strata from the Iona-1 core, SW Texas, where astronomical age modelling gives an age range of 93.92–93.25 ± 0.12 Ma in that section. Outside the USA, it has until now only been recorded from the Cenomanian–Turonian boundary interval in Pakistan.
Review of Palaeobotany and Palynology, 262, 10–16, 2019
https://doi.org/10.1016/j.revpalbo.2018.12.003
NEW ARTICLE PUBLISHED!
Fetchamium prolixispinosum gen. et comb. nov. (division Dinoflagellata)
Martin A. Pearce and Graham L. Williams
Abstract. Oligosphaeridium is a gonyaulacacean dinocyst lacking cingular processes and possessing a distinctive process centred on the antapical plate indicating a sexiform hyposomal tabulation. However, specimens referable to the description of Oligosphaeridium prolixispinosum Davey and Williams, 1966, although lacking cingular processes, are clearly not sexiform. As an additional complication, the holotype of Oligosphaeridium prolixispinosum possesses cingular processes. In this brief contribution, we describe the new genus Fetchamium to accommodate the new transfer Fetchamium prolixispinosum gen. et comb. nov. and provide a discussion and emended diagnosis of the species.
J. Micropalaeontology, 37, 17–20, 2018
https://doi.org/10.5194/jm-37-17-2018
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