Fossil Wood Assemblages Research Articles

Morphometric analysis of some Cretaceous angiosperm woods and their extant structural and phylogenetic analogues: Implications for systematics

Cretaceous fossil wood assemblages provide important evidence about the early evolution of angiosperms. However, the utility of these fossils is limited by two systematic problems: morphotaxa are generally over-split and in many cases cannot be securely assigned to extant families or orders. To address these problems we employed a 16-character Principal Component Analysis (PCA) to critically assess fossil wood systematics and investigate family/order affinity. In the first part of our study, we analyzed a large dataset of woods from extant trees. This served as a test of the PCA method, demonstrating a capability for clustering specimens into natural groups at species, genus, and to a more limited extent, family/order level. Having confirmed the validity of our approach, we then applied it to mid-Cretaceous fossil woods of icacinoid/platanoid and phyllanthoid types. Our PCAs support the distinctiveness of these groups, and most morphogeneric concepts contained therein, but raise significant questions about the uniqueness of many morphospecies. In particular, analyses highlight intra-specific variability as a major problem in delineating morphospecies and confirm suspicions that many taxa are over-split. Comparison of fossil specimens with extant structural and phylogenetic analogues also allows the probable affinity of morphotaxa to be assessed. Among the taxa analyzed, Cretaceous icacinoid/platanoid woods are similar to members of the Icacinaceae and Platanaceae, respectively, but an affinity with the Chloranthaceae or some other basal groups cannot be ruled out. In contrast, phyllanthoid fossil woods may be associated with magnoliid stem of the Laurales and Magnoliales. We argue that our PCA methodology offers a more rigorous and repeatable approach to fossil angiosperm wood systematics compared to those used in earlier studies.

A multi-proxy approach to determine Antarctic terrestrial palaeoclimate during the Late Cretaceous and Early Tertiary

Fossil wood is abundant throughout the Cretaceous and Tertiary sequences of the northern Antarctic Peninsula region. The fossil wood represents the remains of the vegetation that once grew at the southern high palaeolatitudes at 59–62°S through the general decline in climate, from the Late Cretaceous global warmth through to the mid-Eocene cool period prior to the onset of glaciation. This study draws on the largest dataset ever compiled of Antarctic conifer and angiosperm woods in order to derive clearer insights into the palaeoclimate. Parameters including mean annual temperature, mean annual range in temperature, cold month mean, warm month mean, mean annual precipitation are recorded. The fossil wood assemblages have been analysed using anatomical (physiognomic) characteristics to determine the palaeoclimate variables from the Coniacian–Campanian to the middle Eocene. These results are compared with data derived from Coexistence Analysis of the fossil floras (composed of leaves, wood and palynomorphs) and published data based on leaf physiognomic characters. These studies indicate a relatively warm and wet Late Cretaceous that becomes drier and cooler in the Early Paleocene and subsequently returns to warmer, wetter conditions by the latest Early Paleocene. During the Eocene the climate becomes relatively cool and dry once again. The discrepancies obtained from these two methods coupled with other published data are discussed in the context of the fluctuations in the temperatures of the surrounding oceans and global patterns of climate change.

Late Triassic climate in southernmost Parana Basin (Brazil): evidence from dendrochronological data

Dendrochronological methods were used to study a fossil wood assemblage identified as Sommerxylon spiralosus Pires et Guerra-Sommer from outcropping sandstone fluvial sequences (Late Triassic of southernmost Parana Basin, Brazil). The climate signal from fossil woods, supported by sedimentary evidence, indicates a seasonal climate. Analysis of preserved growth rings has yielded information about the peridiodicity of growth related to seasonal cycles. The growth phase in each cycle developed at a slow rate, and the growing period was relatively uniform; in contrast, the periodic phases of growth restriction were not very extensive. These seasonal cycles were interrupted by occasional droughts during the growth season, reflected by the presence of false growth rings. These data match recent global climate patterns from the Late Triassic.

Wheeler, E.A. and Manchester, S.R. Woods of the Eocene nut beds flora, Clarno Formation, Oregon, USA. IAWA Journal, Supplement 3

Wheeler, E.A. and Manchester, S.R. Woods of the Eocene nut beds flora, Clarno Formation, Oregon, USA. IAWA Journal, Supplement 3

Early Last Glacial forest vegetation reconstructed from fossil wood assemblages around Lake Toya, southern Hokkaido, Japan

Early Last Glacial forest vegetation reconstructed from fossil wood assemblages around Lake Toya, southern Hokkaido, Japan

Paleotemperature Estimation from Dicotyledonous Wood Anatomical Characters

Following an earlier study documenting the relationships between wood anatomical features and climate, we examine the utility of dicotyledonous wood assemblages in assessing paleoclimate. The wood anatomy of dicotyledons from modern forest sites in North, Central, and South America, England, Africa, Malaysia, and the Pacific islands was used to derive equations to predict site mean annual temperature. The best equations gave estimates within 5 degrees C at validation sites. Because trees are physiologically active over a wide range in temperature throughout the year, it would be surprising if wood anatomical characters were more finely tuned to temperature. Mean annual temperature (MAT) was estimated from five fossil wood assemblages: Yellow-stone, Wyoming (early Eocene); Clarno Nut Beds, Oregon (middle Eocene); Post, Oregon (late Eocene); Vantage, Washington (middle Miocene); and Fejej, Ethiopia (Miocene). We used the two best equations to estimate paleotemperature at each site; the MAT estimates differed by 0.1 degrees C at Fejej and 5.7 degrees C at Yellowstone, with differences intermediate to these at the other fossil sites. Compared to present-day values, the paleotemperature estimates indicate that, at middle latitudes of the Northern Hemisphere, mean annual temperatures were warmer in the Eocene and Miocene, whereas the near-equatorial Fejej site was the same temperature in the Miocene as it is today. Where possible, we compared the MAT estimates obtained using fossil woods with those obtained using fossil leaves, and found discrepancies of up to 13 degrees C. These differences may, in part, reflect the complicating effect of evolutionary trends in wood anatomical characters that may have been independent of climate change.

Dicotyledonous wood anatomical characters as predictors of climate

Abstract The relationships among wood anatomical characters and climate are examined for 50 wood anatomical features in floras from 37 regions in North America, South America, Africa and Malaysia. Correlations, simple regressions and multiple regressions, were used to develop models for the prediction of climate from wood anatomy. The climate variables considered were: mean annual temperature, mean annual range in temperature, cold month mean temperature, mean annual precipitation, precipitation of the driest month and length of the dry season. Good correlations were found with temperature; poorer correlations with precipitation. The climate variables, especially the temperature-related ones, were best predicted by two or more wood anatomical characters considered together. Characters that we selected to calculate climate variables are: vessels with multiple perforations; spiral thickenings present in the vessels; vessel mean tangential diameter less than 100 μm; fibers septate; rays commonly more than 10 cells wide; rays heterocellular with four or more rows of upright cells; rays storied; axial parenchyma absent or rare; marginal parenchyma present; and wood ring-porous. Models were validated on seven temperate and six tropical sites. Based on these results, a method for determining paleoclimate from fossil wood assemblages is suggested.

Forest development during 6,300–3,000 yBP (Early to Late Jomon Periods) at the Akayama Site, central Japan

Fossil wood assemblages deposited during 6.300–3.000 yBP, are studied at the Akayama Site, central Japan. Layer III containing fossil woods was divided into three subunits according to intercalating tephras, and total 3618 fossil woods were studied. In the composition, deciduous broad-leaved trees dominated, accompanied by some evergreen conifers. In the diameter distribution, nine taxa accounted for nearly 90% of individuals exceeding 10 cm in diameter. Spatial distribution of nine major and three minor taxa and that of thick individuals clarified the following points: 1)Fraxinus established a lowland forest during 5,000–4,500 yBP, accompanied byAlnus sect.Gymnothyrsus, Acer andAesculus turbinata; 2) small trees ofAlnus sect.Gymnothyrsus extensively intermingled in the lowlandFraxinus forest during 4,500–3,000 yBP; 3)Quercus sect.Prinus and Castanea crenata constituted escarpment forests during 6,300–3,000 yBP; 4)Carpinus sect.Eucarpinus became a major component during 5,000–4,500 yBP, andOstrya japonica replacedCastanea crenata during 4,500–3,000 yBP. Comparison with the other five contemporaneous fossil wood assemblages shows prevalence ofFraxinus-dominant forests during the Late to Latest Jomon Periods in the southern part of the Kanto Plain.

Un déterminisme architectural pour les bois de conifères à ponctuation mixte (Protopinaceae Kraüsel, 1917)?

The Mesozoic fossil wood assemblage, the Protopinaceae, have a type of pitting on the radial walls of their tracheids that is now almost extinct. Until now, the proposed explanations for this type of pitting were unsatisfactory. New observations show a connection with tree architecture, and a new hypothesis is proposed. Key words: Protopinaceae, Gymnosperms, Mesozoic, anatomy, architecture, morphology.

開析谷の遺跡とそれをとりまく古環境復元 関東平野中央部の川口市赤山陣屋跡遺跡における完新世の古環境

Paleoenvironmental reconstruction of the Holocene since 8, 000 years ago, based on detailed archaeological excavation and geological and paleobotanical studies, including fossil pollen assemblage, plant macrofossil assemblage, and fossil wood assemblage, has been performed on the sediments in the dissected valley at the Akayama Site (35°50′55″N, 139°45′10″E), about 15km north of Tokyo, in the southeastern part of the Ohmiya Upland, central Kanto Plain. From the results, 5 epoch-making events (E-1 to E-5) and 6 paleoenvironmental stages (I to VI, divided based on their events) were identified. An event is characterized by an erosion and a subsequent drastic change of the sedimentary environment in the valley.Both Stage I(ca 8, 000-6, 500y.B.P.) and Stage II (ca 6, 500-5, 300y.B.P.), corresponding to the Earliest and Early Jomon Ages in archaeology, are characterized by a landslide or collapse of the precipice along the marginal upland ridge, and the reclamation by them or their secondary sediments in a valley under a marine or brackish environment. The sea reached a level 3m above its present level in late Stage I. During both stages, a warm-temperate deciduous broad-leaved forest composed of mainly Quercus subgen. Lepidobalanus stood on the upland to scarp, and Polygonum thunbergii, Chrisoplenium, and Carex communities covered the ridge at the edge of the water, in the valley.Stage III(ca 5, 300-4, 000y.B.P.) corresponds to the Middle Jomon Age, and is distinguished by a standing of Alnus japonica forest in the valley and an invasion of Aphananthe and Celtis in the upland to scarp forest. The deposition of clayey soil containing many Castanea-Castanoposis and Mallotus plant fossils is evidence of the destruction of the forest and the cultivation or semicultivation of Castanea on the scarp to upland.Stage IV (ca 4, 000-2, 200y.B.P.) corresponding to the Late and Later Jomon Ages is defined as an invasion of Fraxinus mandshurica, Aesculus turbinata and Acer to the Alnus forest in the valley, and the beginning of a wide expansion of Cryptomeria, Chamaecyparis group and Quercus subgen. Cyclobalanopsis on the upland. These facts testify to a cooler and wetter climate than that in previous stages. During this stage, part of the bottom forest was destroyed by man, and then manufacturing of Aesculus products was begun.Stage V (ca 2, 200-500y.B.P.) and Stage VI (since 500y.B.P.), later than the Yayoi Age in terms of archaeology, were characterized by a strong impact of man on vegetation and by a swampy valley bottom in which Cyperaceae and Gramineae communities stand. Almost all of the scarp and bottom forests have disappeared mainly as a result of human activities.

Forest reconstruction from fossil wood assemblages in prehistory.

To clarify processes relevant to the formation and deposition of fossil wood assemblages, depositional pattern of fossil woods within a peat bed was studied at the Nakazato Site and the Fukuro-Teichi Site in eastern Tokyo. From the distribution of individual specimens, two different types of fossil wood assemblage have been recognized: one is a buried forest which is discovered in situ, and another is a group of trees that have fallen down into a channel from riverside banks to be deposited there. At the Nakazato Site a Fraxinus-dominant buried forest of the Late to Latest Jomon Period was discovered, and a past community was reconstructed from the distribution of individual specimens. Within the same peat bed, habitat preference of taxa was deduced from difference in composition between blocks farther away from the terrace scarp and those nearer to it. At the same site, two other assemblages of the Kofun Period and Kodai were also detected, and their composition showed strong human impact upon vegetation. At the Fukuro-Teichi Site, the latter type of assemblage was unearthed in a channel of the Late Jomon Period, and its composition strongly reflected very local vegetation beside the channel. With the recognition of processes concerning the formation of fossil wood assemblages, one can estimate the extent of information obtainable from respective assemblages.

Methodological problems in the analysis of fossil non-artifactual wood assemblages from archaeological sites

The analysis of fossil wood fragments is often undertaken in relation to the archaeological excavation of a site. However, such analysis does not yet appear to have the strong methodological foundation that the investigation of many other classes of palaeoenvironmental evidence (e.g. seeds and pollen) have. Consequently, it is difficult to evaluate the value of fossil wood analysis at an archaeological site. Using data regarding non-artifactual wood assemblages at one site in southern Scotland, the relative merits of possible analysis are described and discussed. The results from such analyses tend to fall into two broad groups: (I) those of relatively high reliability, and (2) those of relatively low reliability. The results in the former group are often based on moderately secure methodology and tend to provide relatively non-interpretative information (e.g. species lists). On the other hand, those in the latter group are more often based on insecure interpretive methodology and provide relatively more stimulating information, such as evidence for prehistoric woodland management. There are many reasons for this situation, and these are discussed. In conclusion, it is argued that to increase the reliability of results in the second group (in particular), a full understanding of the taphonomy of non-artifactual fossil wood assemblages is needed, and that once this is available attention can then be paid, as elsewhere in environmental archaeology, to the problems of providing statistically valid samples for analysis.

What Do the Fossil Wood Assemblages Tell us?

What Do the Fossil Wood Assemblages Tell us?