Fossil Leaf Research Articles

Latest Neogene monsoon of the Chotanagpur Plateau, eastern India, as revealed by fossil leaf architectural signatures

A fossil leaf assemblage from latest Neogene (Pliocene) sediments exposed in Jharkhand of Chotonagpur Plateau, eastern India, is subjected to a CLAMP (Climate Leaf Analysis Multivariate Program) analysis using a new high spatial resolution (~1 km2) WorldClim2 gridded climate data and PhysgAsia2 calibration. The CLAMP analysis of 80 different morphotypes of fossil leaves indicates a mean annual temperature (MAT) of 21.9 °C ± 2.3 °C; a cold month mean temperature (CMMT) of 16.7 °C ± 3.5 °C and a warm month mean temperature (WMMT) of 26.9 °C ± 2.9 °C. Precipitation estimates have high uncertainties but suggest a weak monsoon with a growing season (11.7 ± 1 months) precipitation (GSP) of 201.2 ± 64.3 cm. The new calibration also provides for the first time in India more detailed insights into the hydrological regime through the return of annual and seasonal vapour pressure deficit (VPD) and potential evapotranspiration (PET) estimates, as well as new thermal overviews through measures of thermicity and growing degree days. The new results confirm the overall warmth of the region. Although rainfall estimates have large uncertainties due to year-round wet soils, measures of VPD and PET show persistent high humidity, but with higher evaporative stress in the summer during late Neogene times than now.

New species of xeromorphic Banksia (Proteaceae) foliage and Banksia-like pollen from the late Eocene of Western Australia

Banksia microphylla leaf fossils and Banksieaeidites zanthus pollen are newly described from late Eocene lignite of the Zanthus-11 borehole, drilled east of Norseman in Western Australia. The leaf fossils are the first known in Banksia to show extreme narrowness (<1.5 mm wide) combined with the xeromorphic trait of margins rolled onto the lower surface so that the diffusely placed stomata are exposed to the outside environment only via grooves on each side of a thick, abaxial midrib. Both this Banksia leaf type and another with encrypted stomata evolved before the widespread initiation of severe climatic aridity in the late Neogene, likely in regions of edaphic infertility and periodic water stress. New interpretations of leaf morphology and foliar evolutionary pathways in Banksia are proposed. Banksia microphylla probably belongs to subgenus Spathulatae, where it strongly resembles many species in the large, wholly Western Australian clade that includes most species in section Oncostylis, series Abietinae. Banksieaeidites zanthus is morphologically consistent with Banksia pollen, and its extremely small size also suggests placement in Spathulatae. The new fossils and other evidence from Zanthus-11 indicate the local presence of quite open, sclerophyll vegetation with conifers, which was unlikely to have been frequently burnt.

The Cenozoic leaf morphotypes and palaeoclimate interpretation from the Doi Ton Formation, Mae Sot District, Tak Province, western Thailand

The Cenozoic palaeovegetation and palaeoclimate of Doi Ton, western Thailand, megaflora are reconstructed based on physiognomic climate analysis, including Leaf Margin Analysis (LMA), Leaf Area Analysis (LAA), Leaf Size Index (LSI), Climate Leaf Analysis Multivariate Program (CLAMP), and systematic descriptions of each leaf morphotype. The leaf fossils were divided into 23 dicotyledonous leaf morphotypes and two unknown leaf morphotypes. The mean annual temperature results from LMA indicate 32.3 ± 1.17 °C and CLAMP shows 21.2°C. CLAMP also provides temperature data of a warm month mean temperature (WMMT) of 27.4 °C and a CMMT of 14.2 °C, which is similar to the present climate. The mean annual precipitation is estimated by LAA to be ~ 125 cm. CLAMP suggests precipitation in the 11 months of growing period was 154.9 cm with the three wettest months having precipitation of 73 cm, widely contrasting with 15.5 cm for the three driest months. The precipitation shows the signal of the monsoon effect. The temperature, precipitation, and LSI mirrored the vegetation of the contemporary Doi Ton area which is a semi-evergreen forest in the tropical zone. The palaeoclimatic parameters of Doi Ton are in good agreement with those of south China and northwestIndia from the Eocene period and the present-day Mae Sot area. Moreover, the Doi Ton flora also closely matches the humid subtropical modern vegetation of south China. Palaeoclimate and vegetation analysis support an Eocene age estimate for the Doi Ton Formation however further independent age estimates are required to test this working hypothesis.

Miocene flora from the Siwalik of Arjun Khola area, Nepal and its palaeoclimatic and phytogeographic implications

An extensive study on the plant fossils (leaf and fruit impressions/compressions) collected from the Miocene of Siwalik sediments, Arjun Khola area, western Nepal has been carried out. It revealed the existence of a variety of angiosperm plant taxa represented by 43 genera and 47 species belonging to 24 families. Of these, 34 species are reported for the first time from the studied area. Quite a number of fossils out of the entire lot, were described much prior to the present study from other represented by the Siwalik localities. Most of the leaf and fruit specimens are assignable to families of dicots but a single fossil leaf Clinogyne Salisb. has been assigned to the monocot family Marantaceae. The families which are highly represented in the assemblage are Fabaceae, Sapindaceae, Dipterocarpaceae and Annonaceae. Fabaceae which appeared in Upper Paleocene became a major component of the evergreen forest during middle Miocene. A majority of the families are generally represented by leaf forms but Sindora Miq. and Butea Roxb. ex Willd. of the Fabaceae and Terminalia L. of the Combretaceae are represented by fruits. Most of the fossil leaves in the assemblage showed large to medium size with drip tips, entire margins and apparent greater venation density. All the above characters collectively indicated the existence of tropical to sub–tropical type of vegetation during the Miocene all along the Himalayan foot hills of Nepal. Out of the identified specimens, the majority (more than 69%) resembled modern taxa, distributed in the tropical evergreen forests of different geographical regions of the world and recovery of similar looking fossil elements from the Arjun Khola area, indicated existence of similar forest types in and around the area at the time of Siwalik sedimentation. In contrast, the present day vegetation in and around the area is quite different from the past as it includes elements that generally constitute plants of dry deciduous forests. A number of plants migrated from south–east Asia to India via Myanmar and vice–versa. Consequently, many taxa, especially members of Dipterocarpaceae and Fabaceae, existing in south–east Asia in the Paleogene appeared on the Indian subcontinent and Nepal in the Neogene. Phytogeographical data also suggests that taxa flourishing in the Himalayan foot–hills during Siwalik sedimentation have migrated elsewhere in modern times possibly towards south and southeast in search of favourable conditions for luxuriant growth.Present day distribution of all the recovered species from the Siwalik Foreland Basins of Arjun Khola area shows that they are found today in the tropical forests of North–east India, Bangladesh, Myanmar and Malaysia where favourable climatic conditions exist and only little amount of taxa are found to grow presently in the Himalayan foothills. Thus, it may infer that a fair change in floral composition has taken since the Miocene. The nearest living relative (NLR) method of palaeoclimate construction suggests that the Arjun Khola area enjoyed a tropical climate having Mean Annual Temperature (MAT) 22–28ºC and Mean Annual Precipitation (MAP) 2200–3200 mm during the deposition of the sediments.

Fossil leaves from the Cullen Formation (Middle Miocene), Tierra Del Fuego Province, Argentina

Fossil plants in the Tierra del Fuego Province, Argentinean Patagonia, are known since the expedition of Charles Darwin to the Beagle channel. However, only a few fossil plants have been described. In this work, a new fossil leaf collection is studied. It was collected from outcrops of the Cullen Formation (middle Miocene) located in the Atlantic coast of Tierra del Fuego, Patagonia, Argentina. Over two hundred pieces were collected in three localities: Cabo Espiritu Santo, Arroyo Beta, and Canadon de los Mineros. The taxonomic studies reveal the presence of nine fossil species; six of them are related to Nothofagus Blume (Nothofagaceae), one to Myrtaceae, one to Gesneriaceae and the last one to the genus Podocarpus Labill. Our study agrees with previous ones, which suggested that the Nothofagaceae were dominant in the Cullen Formation area, and support the development of a cold temperate and humid forest in the area. The megafloral association studied result similar to others paleofloras developed in Patagonia during the Neogene, according to the cluster analysis performed. Finally, it was characterized like a Subantartic paleoflora sensu Troncoso & Romero.

The Evolution of Functional Traits in Plants: Is the Giant Still Sleeping?

The Evolution of Functional Traits in Plants: Is the Giant Still Sleeping?

Fossil Podocarpus (Podocarpaceae) from the lower Pliocene of Tengchong, Yunnan Province, China and its biogeographic significance

ABSTRACT Numerous pollens and a few wood fossils with probable affinity to Podocarpus L’Heritier ex Persoon have been discovered from China. However, the leaf fossils of Podocarpus were not well documented. In this study, we describe a new species, Podocarpus pliomacrophyllus sp. nov., from the lower Pliocene of Tengchong, western Yunnan, southwestern China, with detailed cuticular structures. According to gross morphology and cuticular structure of leaves, the present species mostly resembles extant P. macrophyllus (Thunberg) Sweet, which is attributed to the subgenus Foliolatus de Laubenfels. Molecular data support that the genus Podocarpus derived from Gondwana, and the subgenus Foliolatus diverged from the subgenus Podocarpus during the early Miocene. Therefore, the present fossils from Tengchong indicate that the subgenus Foliolatus had spread from India to western Yunnan before the early Pliocene, and then to southeastern China. The Pleistocene glacial events forced Podocarpus to retreat from western Yunnan and the uplifted Hengduan Mountains hindered its reconnection during the subsequent warm interglacials.

Constructing a time scale of biotic recovery across the Cretaceous–Paleogene boundary, Corral Bluffs, Denver Basin, Colorado, U.S.A.

ABSTRACT The Cretaceous–Paleogene (K–Pg) boundary interval represents one of the most significant mass extinctions and ensuing biotic recoveries in Earth history. Earliest Paleocene fossil mammal faunas corresponding to the Puercan North American Land Mammal Age (NALMA) are thought to be highly endemic and potentially diachronous, necessitating precise chronostratigraphic controls at key fossil localities to constrain recovery dynamics in continental biotas following the K–Pg mass extinction. The Laramide synorgenic sedimentary deposits within the Denver Basin in east-central Colorado preserve one of the most continuous and fossiliferous records of the K–Pg boundary interval in North America. Poor exposure in much of the Denver Basin, however, makes it difficult to correlate between outcrops. To constrain fossil localities in coeval strata across the basin, previous studies have relied upon chronostratigraphic methods such as magnetostratigraphy. Here, we present a new high-resolution magnetostratigraphy of 10 lithostratigraphic sections spanning the K–Pg boundary interval at Corral Bluffs located east of Colorado Springs in the southern part of the Denver Basin. Fossil localities from Corral Bluffs have yielded limited dinosaur remains, mammal fossils assigned to the Puercan NALMA, and numerous fossil leaf localities. Palynological analyses identifying the K–Pg boundary in three sections and two independent, but nearly identical, 206Pb/238U age estimates for the same volcanic ash, provide key temporal calibration points. Our paleomagnetic analyses have identified clear polarity reversal boundaries from chron C30n to chron C28r across the sections. It is now possible to place the fossil localities at Corral Bluffs within the broader basin-wide chronostratigraphic framework and evaluate them in the context of K–Pg boundary extinction and recovery.

On geologic timescales, plant carbon isotope fractionation responds to precipitation similarly to modern plants and has a small negative correlation with pCO2

Leaf carbon isotope fractionation (Δleaf) is sensitive to environmental conditions and can provide insights into the state and evolution of leaf gas-exchange in response to climate and environment factors. In modern plants, water availability is the strongest environmental predictor of Δleaf across sites that experience relatively uniform and low concentrations of CO2 in the atmosphere (pCO2). Growth chamber experiments show Δleaf of modern plants can also be sensitive to changing pCO2. However, over geologic time, it is uncertain how Δleaf has responded to shifts in pCO2 and precipitation. To address this problem, we collected sediment (rock) samples from fossil leaf sites that represent a range of pCO2 values from ∼200 to 900 ppmV, over 40 degrees of latitude from New Mexico to the High Arctic, and 40 million years spanning the Late Cretaceous to the Oligocene. For each site, the carbon isotope composition of atmospheric CO2 (δ13Catm), pCO2, mean annual precipitation, and mean annual temperature were constrained from independent proxies. From sediment samples, we extracted long-chain n-alkanes (biomarkers derived from plant wax). We then measured the carbon isotope ratios of sediment-derived n-C29 and n-C31 alkanes to calculate Δleaf. Results show a negative correlation between Δleaf and pCO2 even after controlling for mean annual precipitation. The Δleaf response to pCO2 is small (−0.3 ± 0.09‰/100 ppmV), suggesting plants are adjusting internal leaf CO2 concentrations to atmospheric pCO2 concentrations, likely by optimizing leaf gas-exchange to maximize carbon intake and minimize water loss in response to environmental conditions. Similar to previous studies of geologic sediments and living plants, Δleaf was also positively correlated with water availability and, to a lesser extent, sensitive to plant type and possibly altitude. As a result, the Δleaf – pCO2 relationship in the geologic past may be more complex than observed in modern studies and therefore, precludes its use as a pCO2 proxy.

The Pliocene flora of Frankfurt am Main, Germany: taxonomy, palaeoenvironments and biogeographic affinities

The Pliocene flora of Frankfurt am Main described by Karl Mädler during the first half of the twentieth century is a key flora for the European Pliocene. In the present study, we revised the leaf fossil taxa described by Mädler and investigated plant material collected after Mädler’s publication. The revised and augmented floral list comprises seven new species and some new combinations of taxa described by Mädler. In total, 16 gymnosperm species in 15 genera and 73 angiosperm species (of which 15 could not be assigned to a genus) in 40 genera are recognised in the leaf record. Main characteristics of the flora are the high diversity of conifers, the diverse assemblage of exclusively deciduous Fagaceae, including six species of oaks, and the high diversity of Rosaceae. These features indicate cool temperate climatic conditions (comparable to Lugano in southern Switzerland). Angiosperm genera that are today confined to North America and/or East Asia (Eucommia, Magnolia and Sassafras) also are deciduous, whereas evergreen taxa are shrubs typical of the understorey (Buxus, Ilex, Pachysandra, Prunus lusitanica type) and Viscum. Eighteen taxa recorded in the Pliocene of Frankfurt am Main are today absent from western Eurasia and eastern North America, and 25 taxa are absent from western North America. This shows (i) a strong biogeographic link of the Pliocene flora of Frankfurt am Main with East Asia, (ii) surprisingly high levels of speciation (Pliocene endemisms) and (iii) that the European flora was more diverse in woody species shortly before the onset of major Pleistocene glaciations than today.

Late Cretaceous domatia reveal the antiquity of plant-mite mutualisms in flowering plants.

Mite houses, or acarodomatia, are found on the leaves of over 2000 living species of flowering plants today. These structures facilitate tri-trophic interactions between the host plant, its fungi or herbivore adversaries, and fungivorous or predaceous mites by providing shelter for the mite consumers. Previously, the oldest acarodomatia were described on a Cenozoic Era fossil leaf dating to 49 Myr in age. Here, we report the first occurrence of Mesozoic Era acarodomatia in the fossil record from leaves discovered in the Upper Cretaceous Kaiparowits Formation (76.6-74.5 Ma) in southern UT, USA. This discovery extends the origin of acarodomatia by greater than 25 Myr, and the antiquity of this plant-mite mutualism provides important constraints for the evolutionary history of acarodomatia on angiosperms.

The Loss of a Unique Palaeobotanical Site in Terceira Island Within the Azores UNESCO Global Geopark (Portugal)

Terceira Island (Azores archipelago, central Atlantic Ocean) presents a unique but poorly studied Quaternary palaeobotanical record. Among the sites referenced in the literature, Fanal Bay, within Angra do Heroismo city, is known at least since the 1940s. Field prospection in the summer of 2016 revealed two layers of leaf fossils with an unexpected fossil abundance. The preliminary results showed that these represented autochthonous or para-autochthonous (T0) fossil assemblages, preserved by the emplacement of ash or lapilli layers by volcanic events, in a leaf litter of a laurel palaeoforest. Unfortunately, in 2018, the site was destroyed due to development works to consolidate and requalify the Fanal Bay cliff from further sea erosion. This prevented a detailed study and the ex situ preservation of an important palaeontological site, within the Azores UNESCO Global Geopark. With this work, we hope to call the attention to the need of implementing geoconservation strategies in order to prevent the destruction of important geoheritage within the Azores Islands and to transpose this warning to other geoconservationists in oceanic islands worldwide.

How diverse were ferns in the Baltic amber forest?

AbstractDiverse temperate forest types and a high atmospheric humidity have recently been suggested for the Eocene source area of Baltic amber. However, ferns are astonishingly rare as inclusions in this amber, which is in contrast to other seed‐free land plants, fungi, and lichens. Moreover, the identities of some of the few described putative fern taxa are dubious, and some fossils were even assigned to the Paleozoic seed fern genera Alethopteris, Pecopteris and to the form genus Sphenopteris containing Paleozoic and Mesozoic fern‐like leaf fossils. Here, we review previously described fern inclusions from Baltic amber and identify further fern‐like leaf inclusions as belonging to the extant angiosperm genus Comptonia (sweet ferns, Myricaceae). We conclude that only one taxon, Matonia striata (Matoniaceae), can with confidence be identified as a Polypodiopsida representative. Although “Pecopteris” humboldtiana is so far only known as sterile foliage, its leaf morphology strongly suggests that also this taxon belongs to the Polypodiopsida rather than to any other tracheophyte lineage. We propose accommodating “Pecopteris” humboldtiana in the new genus Berendtiopteris. “Alethopteris” serrata and “Sphenopteris” phyllocladoides are not to be regarded as evidence of ferns from Baltic amber. Reinvestigation of the holotypes of these two taxa did not reveal to which tracheophyte lineages these fossils belong. We suggest that the scarcity of fern remains from Baltic amber may reflect both a relatively low fern diversity in the source area of the fossil resin, and an absence or rarity of epiphytic and climbing ferns as observed in modern temperate forest ecosystems.

A new foliicolous melioloid fungus from the Pliocene of eastern Himalaya

We report the in situ occurrence of a new species of Meliolinites (fossil Meliolaceae, Ascomycota), Meliolinites pliocenicus, on the lower epidermal surface of fossilized angiosperm leaf of Shorea siwalika (Dipterocarpaceae) recovered from the middle Siwalik stratum (Subansiri Formation: Pliocene) of Arunachal sub-Himalaya. This fungal morph is characterized by well-preserved unique mycelia consisting of superficial, dark brown, thick-walled, branching hyphae with appressoria as well as phialides and dispersed ellipsoidal, 3-septate, 4-celled, dark brown ascospores. The in situ evidence of the fungus on the fossil leaf cuticle indicates the prevalence of a warm, humid, tropical climate in Arunachal sub-Himalaya during the deposition and further suggests that a possible host-ectoparasite relationship existed in the ancient forest of this area during the Pliocene time.

A new meliolaceos foliicolous fungus from the Plio-Pleistocene of Arunachal Pradesh, eastern Himalaya

We report in this article, the in situ occurrence of a new species of Meliolinites (fossil Meliolaceae), Meliolinites neogenicus sp. nov. on the abaxial cuticular surface of fossilized leaf cuticle fragments of the angiosperm Litsea cf. salicifolia Khan et al. (Lauraceae) recovered from the upper part of the Siwalik succession of Neogene sediments (Kimin Formation: late Pliocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya, India. This Plio-Pleistocene melioloid foliicolous fungal morph features a well-preserved unique mycelium consisting of superficial, dark brown, thick-walled and branching hyphae with bicellular appresoria and unicellular phialides. The fungal colonies also include globose, dark brown perithecia, as well as one ellipsoidal, 5-celled, 4-septate, dark brown ascospore. The fossil leaf of Litsea, together with the foliicolous fungal remains indicates the prevalence of a warm, humid, climate in the Arunachal sub-Himalaya during the Plio-Pleistocene. The in situ evidence of Meliolinites on host leaf cuticle indicates the possible existence of a host–ectoparasite relationship in the ancient warm and humid tropical evergreen forest of this area during the Plio-Pleistocene. Based on present and earlier records it is suggested that Lauraceae has been a common host for meliolaceous fungi since the early Cenozoic. Meliolinites neogenicus sp. nov. might have thrived under a warm and humid climate with a mean annual temperature (MAT) from 21 to 26 °C and a mean annual precipitation (MAP) from 1000 to 2000 mm in the Plio-Pleistocene of Arunachal sub-Himalaya which is in conformity with our earlier published qualitative and quantitative climatic data.

The Miocene flora of Alum Bluff, Liberty County, Florida

Abstract The plant fossils of Alum Bluff, northwestern Florida, provide a unique insight into the rarely preserved Miocene flora of the eastern United States. A century has passed since the introductory treatment on the fossil leaf flora of Alum Bluff. More specimens have accumulated over the past two decades, allowing for an updated evaluation of the megafossil flora following a recent study of the palynoflora. The strata consisting of poorly consolidated sand and siltstones with intervening clay layers, here recognized as the Fort Preston Formation of the Alum Bluff Group, are considered to be of Barstovian age (16.3–13.6 Ma), based on co-occurring mammalian remains. Here we recognize 36 kinds of leaves and 10 kinds of fruits and seeds, giving a minimum estimate of at least one fungus, one fern, one gymnosperm, 38 angiosperms and 7 unknowns. We also report one new species and two new combinations. These taxa augment those already reported based on pollen from the same strata, allowing us to portray the vegetation as elm-hickory-cabbage palm forest occurring near the coastline in a deltaic, pro-deltaic, or intertidal shore face environment. The results of a climate analysis of the Alum Bluff flora, using leaf margin and leaf area, give estimates of 19.0°C mean annual temperature and 116.0 cm mean annual precipitation.

Early Miocene climate and biomes of Turkey: Evidence from leaf fossils, dispersed pollen, and petrified wood

The early Miocene was a period of major palaeogeographic reorganization in the eastern Mediterranean region, during which time the Anatolian Plateau became subaerial and several intracontinental basins intermittently became connected to the Paratethys and Mediterranean seas. In this paper, we analyse early Miocene vegetation and climate using leaf records, palynological assemblages, and fossil wood at 36 localities from western and central Turkey, most of which have precise age control based on radiometric dating and mammal faunal ages. Using the leaf flora of Güvem (Beş Konak, Keseköy), Climate Leaf-Analysis Multivariate Program (CLAMP) analyses and Köppen signatures were employed to infer a palaeoclimate typical of modern laurel forest regions. Based on the palynological records, abundance of various pollen-taxa was used as a measure of openness of vegetation and regional presence of major tree taxa. Most pollen floras are dominated by tree pollen (ranging from 85 to 98%) and indicated widespread afforestation. In the pollen diagrams, shifts in dominance from swamp forest elements (Taxodioideae) to well-drained forests (Pinaceae) indicate changes in lake levels or phases of basin development. Such shifts may have been associated with the development of more xeric forest vegetation. Wood anatomical features such as false tree rings further may indicate seasonal climate. Pollen diagrams and macrofossils reflect zonal and azonal broadleaf and needleleaf forest and extrazonal open vegetation. The latter occurred in areas with shallow soils on volcanic rocks or limestone (e.g. cycads, Dracaena), or coastal areas (herb dominance). Taxonomic composition and biogeographic affinities suggest laurel forest as a major forest biome on well-drained soils and ecotones between laurel forest and broadleaf deciduous forest biomes. A comparison with younger floras shows that these are neither more diverse nor more warmth-loving despite an increase in global temperature (Mid-Miocene Climatic Optimum) suggesting bottlenecks during previous (Oligocene) cooler times for warmth-loving taxa.

The Pleistocene flora of Bezhan, southeast Albania: early appearance of extant tree species

ABSTRACT The piggyback basin of Bezhan, southeastern Albania, was formed during the late Neogene and contains Pliocene/Pleistocene deposits. These continental deposits consist of marls, siltstones and clays separated by a thin series of lignite-seams alternating with clays (Bezhan formation). We investigated leaf fossils and dispersed pollen from marls of the upper portion of this formation. Fifty-two plant taxa comprising algae, gymnosperms, and angiosperms were recovered. Of these, at least 19% belong to extant species and less than 16% belong to taxa today extinct in western Eurasia. Tsuga is represented by three pollen taxa with affinities to modern Chinese, Japanese, and North American species. Herbaceous taxa indicative of steppe (Artemisia, Amaranthaceae) occur in low quantities (≤1%) suggesting an interglacial setting. Four vegetation units are recognised: Wet riparian and aquatic vegetation, mesic oak forest, dry sub-Mediterranean woodland, and montane conifer forest. A comparison of the Bezhan flora with well-dated Pliocene and Pleistocene floras of Italy suggests a Calabrian (late early Pleistocene) age for the upper unit. This estimate is based on the abundance of extant taxa, the absence of subtropical taxa, and threshold values of particular taxa (Tsuga, Carya). The findings are in agreement with age estimates for extant tree species from molecular studies.

A novel approach for predicting the probability of ignition of palaeofires using fossil leaf assemblages

AbstractMany metrics are used to predict and manage wildfires today but it is difficult to directly apply these to past wildfires histories. Developing an approach that enables estimation of these fire metrics in the past would provide significant power in our ability to compare past fire risk with that of the modern day. We use the Climate Leaf Analysis Multivariate Program (CLAMP) to estimate warm month mean temperature and annual mean relative humidity for a modern day leaf dataset and establish a novel methodology by which we can generate ‘pseudo‐daily’ meteorological parameters to calculate the probability of ignition (p(I)), an aspect of the North American Fire Danger Rating System. We test this methodology on Tortonian aged fossil leaves (11.62–7.25 Ma) from five sites across California, which reveal that the Tortonian was cooler and considerably more humid and that p(I) was lower during this time than in the region today.

An Oligocene microthermal forest dominated by Nothofagus in Sierra Baguales, Chilean Patagonia: Response to global cooling and tectonic events

A large fossil leaf assemblage (>3700 specimens) is reported from the Oligocene Río Leona Formation in the Sierra Baguales of Chilean Patagonia. The association comprises 29 species but is dominated by Nothofagus genera, which constitutes 65% of specimens. The collection can be classified as a Mixed Palaeoflora of the Austral-Antarctic association. Stratigraphic analysis of the assemblage indicates a decrease in species diversity and richness over time, which was accompanied by species turnover. Quantitative studies of foliar morphology (CLAMP, Leaf Margin Analysis) indicates cool-to-cold and dry climatic conditions, with a Mean Annual Temperature of 9.2 °C, a relatively high seasonality in temperature and precipitation, and a Mean Annual Precipitation of 931 mm. Nothofagus only became dominant in southeastern Patagonia during the Rupelian, coinciding with a marked global cooling period linked to the initiation of glaciation in Antarctica about 34 Ma. The decrease in precipitation following this event is attributed to the development of a rain shadow to the east of the rising Southern Patagonian Andes, which must have been of the order of 1000 m or more for topographic climate forcing to take effect. This contrasts with the rain shadow development east of the Andes at lower latitudes, which was mainly manifested after the middle Miocene.