Ian J. Glasspool

Charcoal in the Silurian as evidence for the earliest wildfire

Rare basal Pridoli plant fossils, which resemble the rhyniophytoid Hollandophyton colliculum and have exceptional three-dimensional cellular anatomy, are preserved as charcoal. As such, these fossils from Ludford Lane in the Welsh Borders are evidence of the earliest recorded wildfire and are the first documented from before the Devonian. The fossils represent the charred remains of a low-growing, low-diversity, in situ rhyniophytoid or cryptospore-bearing plant vegetation charred during a low-temperature fire.

Charcoal reflectance as a proxy for the emplacement temperature of pyroclastic flow deposits

Hot pyroclastic flow deposits often entomb and preserve vegetation as charcoal. When studied in polished section, this charcoal is highly reflective. Novel data from experimentally charred woods demonstrate that reflectance increases with both temperature and time. At temperatures above 250 °C, reflectance rises rapidly for the first hour, effectively stabilizing after 4 h for temperatures below 400 °C. However, for higher temperatures, reflectance only stabilizes after ∼24 h. Charcoalified woods from block and ash flow deposits generated by the Soufriere Hills volcano in Montserrat have yielded interpreted deposit temperatures, based on reflectance data, of 325–525 °C. These temperatures compare favorably with directly measured data (365–640 °C) from the same deposits, indicating that charcoal reflectance is useful as a temperature proxy for ancient pyroclastic flow deposits, particularly where magnetic or mineral data are absent for this purpose. However, caution should be exercised, as only a minimum temperature can be inferred where the heating duration of the deposit is unknown. Unlike magnetic or mineral data, temperature data from charcoalified woods can be obtained from reworked deposits, providing a valuable means of validating observations made about the style of eruption of volcanoes in ancient settings.

A major fire event recorded in the mesofossils and petrology of the Late Permian, Lower Whybrow coal seam, Sydney Basin, Australia

Abstract Petrographic and mesofossil analyses of plies from the Late Permian, Lower Whybrow coal, New South Wales, Australia have revealed a significant fire event in both the swamp setting and the hinterland. The fire event is characterised by a change in the maceral composition, the seam during this interval being dominated by inertinite, especially semifusinite. Following the fire event, the mineral matter content of the coal increases. This may be the result of increased run-off and erosion in the hinterland due to destruction of vegetation. This major fire event is also reflected in a change in the vegetation, as represented by the mesofossil content of the seam. Prior to the fire event the seam contains abundant bisaccate taeniate pollen sporangia and seed-like bodies of possible glossopterid affinity. These are lost at the ply in which the fire event is recorded; though seed-like bodies become important again later. The fire event also corresponds to a change in the megaspore content of the coal, a new species appearing, perhaps as a result of hydrological change. Following this major fire event, a mineral rich ply was deposited which contains miospore masses of spores from fern-like plants, possibly representing a re-colonisation event by rhizomorphs after vegetation death. This evidence for a major fire, and its implications for the origin of inertinites, leads to the conclusion that throughout this, and other Permian Gondwana coals, fire was an integral part of the temperate, mid–high latitude, southern hemisphere swamp ecosystem.

Episodic fire, runoff and deposition at the Palaeocene–Eocene boundary

Qualitative and quantitative coal petrological analyses have been undertaken on the laminated lignite at the base of the Cobham Lignite Bed, from Scalers Hill, Kent, England. The maximum negative carbon isotope excursion, which marks the beginning of the Palaeocene–Eocene thermal maximum (PETM), occurs near the top of the laminated lignite. The lignite contains inertinite, a petrographic term used to describe charcoal. The laminated lignite has inertinite-rich and inertinite-poor layers indicative of episodic fires and post-fire erosion. Charcoal clasts are derived from living or recently senesced plants and are dominated by the leaf stalks of herbaceous ferns and wood fragments from flowering plants. The charcoal assemblage reflects a low-diversity flora, possibly adapted to disturbance by fire, derived from a source vegetation subjected to seasonal surface wildfires. The environmental conditions leading up to and across the onset of the PETM are, therefore, interpreted as incorporating a persistent fire regime with episodic wildfires followed by rainfall and runoff events. Abundant charcoal indicates near-modern oxygen levels whereas the absence of charred peat in this area calls into question previous suggestions that burning of Palaeocene peats might have contributed to the short-lived negative carbon isotope excursion at the Palaeocene–Eocene boundary.

Foliar herbivory in Late Palaeozoic Cathaysian gigantopterids

Foliar feeding traces as evidence of plant^animal interaction are reported for the first time on gigantopterid plants from the Late Palaeozoic Cathaysian flora. Frequently occurring marginal, non-marginal and apical leaffeeding traces have been identified in two gigantopterid species, Gigantonoclea lagrelii and Gigantonoclea hallei, from the late Early to early Late Permian Shihhotse Formation in northern China. However, foliar herbivory is not recorded on the third gigantopterid present in the same formation, Cathaysiopteris whitei, indicating selective feeding strategies within Cathaysian gigantopterids and the preferential targeting of leaves of Gigantonoclea. Abundant foliar herbivory within Gigantonoclea from the Shihhotse Formation is in stark contrast with many other elements of the same floral assemblages, including plants such as marattialean ferns, sphenophytes and certain other seed-ferns in which foliar herbivory has not been observed. The occurrence of herbivory within gigantopterids from the Cathaysian realm is discussed, and other kinds of plant^animal interactions from Cathaysian floras are summarised in order to present a synthesis to compliment similar data collected for the Late Palaeozoic floras of Euramerica. These new data on foliar herbivory, combined with other evidence of plant^animal interactions in Cathaysian floras, indicate unusually high levels of herbivory on certain gigantopterids compared to previous ideas of foliar herbivory in the Palaeozoic. In combination with evidence previously reported from Euramerica, our results testify to the widespread nature of foliar herbivory on Late Palaeozoic gigantopterids.

Pennsylvanian paleokarst and cave fills from northern Illinois, USA: A window into late Carboniferous environments and landscapes

Abstract A new fault-associated paleokarst and cave fill has been discovered in north-central Illinois, emplaced in Ordovician limestones. The paleokarst preserves many original solution features, such as oriented grooves, pendants, and half tubes. Many of the ancient cave passages have rounded bottoms and flat roofs. Together these suggest that the original elliptical, phreatic cave passages grew upward by paragenesis, in which the floor of the cave is protected from dissolution by the presence of sediment, while the ceiling of the cave grows upward by dissolution. The fill is dated as Moscovian (Middle Pennsylvanian) based on palynological data and can be correlated with the Tradewater Formation. The fills are composed of a fining-upward sequence of relatively unindurated clastic sediments that contain well-preserved plant fossils, most notably voltzialean conifer and cordaite remains, representative of vegetation living in well-drained areas. Many of the macrofossils are fragmentary but charcoalified and, along with the megaspores, are uncompressed and preserve exceptional morphological and anatomical data. The presence of abundant charcoal in the fills, as well as diagnostic polycyclic aromatic hydrocarbons, indicates significant wildfire activity in this area during this interval.

Palynological evidence of vegetation dynamics in response to palaeoenvironmental change across the onset of the Paleocene‐Eocene Thermal Maximum at Cobham, Southern England

A high‐resolution palynological study is undertaken through the Cobham Lignite Bed (Cobham, Kent, UK) to investigate vegetation response to the rapid climate warming at the onset of the Paleocene‐Eocene thermal maximum (PETM). The lower laminated lignite records negative carbon isotope (δ 13C) excursions (CIE) (marking the PETM onset) in bulk organic material, n‐alkanes and, uniquely, also in hopanes. The upper blocky lignite represents an estimated 4–12 kya after PETM onset. Raw and rarefied palynomorph species richness measures are higher in the PETM but the difference is not statistically significant. Only five (of 24) common taxa have last appearance or major shifts in percentage occurrence close to the PETM onset. One of these, a triporate eudicot, occurs only in the maximum negative CIE sample and the immediately underlying sample, the former at very high percentages, an interesting feature of PETM onset. The palynomorph composition of Late Paleocene samples is significantly different from PETM samples. In the late Paleocene there is a close association of high abundances of Cicatricosisporites (Schizaeaceae) fern spores with microscopic and mesoscopic charcoal representing a low diversity fire prone fern and woody angiosperm community. By contrast, the PETM vegetation is characterised by the loss of ferns and cessation of fires, an increase in wetland plants (including cupressaceous conifers) and a more varied flowering plant community with palms and eudicots. These palynofloras thus indicate little response in plant species across the PETM onset but a major change in vegetation composition, linked to a switch in fire regime.

Radiation and extinction patterns in Permian floras from North China as indicators for environmental and climate change

Abstract: Permian continental sequences from North China contain previously unrecognized episodes of plant radiation and elevated extinction. The earliest extinction, in the Lower Shihhotse Formation (Roadian, Guadalupian), records a 45% floral species loss and is tentatively correlated with global extinctions amongst dinocephalian reptiles. Two younger extinctions are dated by correlating the Illawara Reversal and palaeomagnetic polarity sequences from Shanxi Province against global palaeomagnetic history. Missing data from the Shanxi sequence are evaluated using a novel approach estimating likely maximum and minimum sequence changes that provide age estimates for post-Illawara events in North China. The second extinction in the middle Upper Shihhotse Formation is more significant and is dated to the mid-Capitanian, with a loss of 56% of plant species coinciding with two phases of volcanism of the Emeishan Large Igneous Province in South China, previously linked to the mid-Capitanian marine mass extinction. The youngest extinction in the upper Upper Shihhotse Formation (late Capitanian to mid-Wuchapingian) is catastrophic and represents the end of range in the sequence. Changes in sedimentary facies suggest it to be related to global climatic warming and drying. Other viable causal mechanisms for the extinction episodes include plate motion and collision, global climate change, volcanism and biological competition.

An Upper Permian permineralized plant assemblage in volcaniclastic tuff from the Xuanwei Formation, Guizhou Province, southern China, and its palaeofloristic significance

A new permineralized fossil plant assemblage is described from volcaniclastic tuff collected in the Upper Permian (Wuchiapigian to Changhsingian) Xuanwei Formation at Shanjiaoshu mine, Guizhou Province, China. The assemblage is fragmentary but contains a small sphenopsid strobilus, a partial strobilus of a lepidodendralean lycopsid, pinnae of the filicalean fern Anachoropteris and a filicalean non-laminate fertile pinna rachis, the marattialean ferns Eoangiopteris , Scolecopteris and Psaronius , hooked stems of probable gigantopterid affinity, and two kinds of cardiocarpalean ovules. This represents the first indisputable evidence of Anachoropteris from the Permian of China, and contrasts with previous evidence from Europe and North America that indicates this genus became extinct during earliest Permian times. The assemblage highlights the persistence of plants from wetland communities and mire ecosystems into the Upper Permian of southern China, and adds further support to the presence of the Ameriosinian phytogeographical realm. This represents the first record of a plant assemblage preserved in volcaniclastic sediments from the Upper Permian of southern China, and in combination with other recently discovered plant assemblages in similar deposits in southern China, suggests volcanism to be an important factor in facilitating permineralized plant preservation in this realm. Although the source of the volcanism that produced the tuff is unknown, its age and location are consistent with the Emishan Large Igneous Province (LIP) of southwest China.

Hypautochthonous–allochthonous coal deposition in the Permian, South African, Witbank Basin No. 2 seam; a combined approach using sedimentology, coal petrology and palaeontology

Abstract A suite of techniques, including coal petrology, micropalynology, mesofossil analysis, and macroscopic appearance has been used to examine the Early Permian, South African, Witbank Basin No. 2 seam from a sample locality near Ogies. This coal appears to be similar in its palynological and petrographic composition to other coals of this interval from this basin. However, its accumulation appears to have been largely hypautochthonous or allochthonous evidenced by, erosive contacts, small scale cross-laminations, and fine lenticular bodies being recognised within the coal seam profile. This ex situ deposition probably, in part, relates to frequent wildfire activity, which may have promoted subsequent run-off and erosion, and led to the numerous mineral-rich horizons observed in the sample seam profile. In addition to the sedimentological characters described above, the petrology of the seam and its mesofossils, most particularly megaspores from a lycopsid parent vegetation, indicate saturated peat-forming conditions. However, examination of charred mesofossil fragments indicates periods of low humidity and even drying of the peat itself rendering it liable to combustion. These contradictory characters may indicate seasonality and suggest a coldness of the climate, at least for part of the year, that could account for the retardation of peat decay during these drier intervals. These characters can be reconciled with deposition during an interglacial phase as the Dwyka glaciation terminates, as has previously been proposed for the Witbank Basin No. 2 seam.