Showing papers by "Margaret E. Collinson published in 2012"
TL;DR: In this article, a comprehensive compilation of literature on global Cretaceous charcoal occurrences shows that from the Valanginian on, terrestrial sedimentary systems frequently preserve charcoal in abundance, indicating that fires were widespread and frequent.
113 citations
25 Jul 2012
TL;DR: Fossil Fruits and Seeds of the Middle Eocene Messel biota, Germany, the authors, fossil fruits and seeds of the middle eocene Msel biota.
Abstract: Fossil Fruits and Seeds of the Middle Eocene Messel biota, Germany , Fossil Fruits and Seeds of the Middle Eocene Messel biota, Germany , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
110 citations
TL;DR: In this paper, two randomly sampled in situ coal pillars (seams 78 and 88) from the Late Permian Kuznetsk Basin, Siberia, were analysed using petrographic techniques to determine palaeowild fire histories (fire occurrence, type and return interval).
53 citations
TL;DR: For a short time interval (c. 1.2myr) during the early middle Eocene (~ 49 myr), the central Arctic Ocean was episodically densely covered by the freshwater fern Azolla, implying sustained freshening of surface waters as mentioned in this paper.
30 citations
TL;DR: The combination of strongly ornamented monocolpate pollen grains permanently united in tetrahedral tetrads is unusual and to the best of the authors' knowledge has not been reported previously in a gymnosperm.
Abstract: Ricciisporites tuberculatus Lundblad is a prominently sculptured palynomorph that is permanently united in tetrads. This palynomorph has a wide geographic distribution and reaches a stratigraphically important acme in the Late Triassic of Europe, Greenland, and Arctic Canada. This palynomorph has not yet been found in situ in a fossilized reproductive structure, and consequently its botanical affinity is unclear. Some authors have suggested that R. tuberculatus was produced by a seed plant, but others have suggested that this palynomorph was produced by a liverwort comparable to Riccia. In order to clarify the botanical affinity of R. tuberculatus, we have analyzed its morphology using SEM and TEM. Individual grains within the tetrad are equipped with a single distal colpus, and the ultrastructure of the palynomorph wall is characterized by a granular inner sexine and an electron-dense laminated nexine. These morphological features ally R. tuberculatus to the gymnosperms. The combination of strongly ornam...
29 citations
TL;DR: X-ray tomographic methods have revealed important features of Messel specimens, which have provided key taxonomic characters and supported recognition of new taxa, some of which are the earliest fossil representatives of modern genera.
Abstract: X-ray tomographic methods have been evaluated for their suitability to visualise morphology and anatomy of fossil fruits and seeds preserved in the oil shale of the Middle Eocene Messel Formation (former Lake Messel, near Darmstadt, Germany). Micro-computed tomography (microCT) is suitable for evaluation of gross morphology and tissue preservation. Synchrotron radiation X-ray tomographic microscopy (SRXTM) enables visualisation of gross morphology, tissues, and their detailed cellular structure. Of 30 taxa studied, only 4 exhibit good cellular detail. The reason for lack of detail in other taxa is unclear but may be related to subtle variations in chemical composition or physical structure of their tissues. X-ray tomographic data also permit structures, such as locule casts, to be visualised, giving additional features for comparison with other extinct and extant taxa. X-ray tomography has revealed important features of Messel specimens, which have (1) provided key taxonomic characters and supported recognition of new taxa, some of which are the earliest fossil representatives of modern genera (Pleiogynium, Anacardiaceae; Berchemia, Rhamnaceae), (2) demonstrated the absence of modifications for epizoochory in this flora, and (3) revealed aspects of exceptional preservation relevant to mammal and bird diet (e.g. soft tissue in fruits of Vitaceae).
17 citations
TL;DR: A wide array of purported impact proxies from a lacustrine paleo-record in Lake Cuitzeo, Mexico were outlined, extending the range of such markers to Mexico and allowing the proponents of the YD Impact Hypothesis to respond to the many critiques of theYDIH.
Abstract: The recent article by Israde-Alcantara et al (1) outlined a wide array of purported impact proxies from a lacustrine paleo-record in Lake Cuitzeo, Mexico These findings were used to support the suggestion of a Younger Dryas (YD) impact event/s Although most of the purported impact proxies have been described in previous publications (2, 3), this new work extended the range of such markers to Mexico The article also allowed the proponents of the YD Impact Hypothesis [YDIH] to respond to the many critiques of the YDIH
3 citations