Fossil Wood

This paper presents the results of the incisive geo-archaeological explorations carried out in parts of the Khowai, Hoara and Sonai river valleys in Tripura. This was undertaken as part of the Field Trip Project of the 36th International Geological Congress (IGC). Extensive and systematic Quaternary mapping in the 1980s by the Geological Survey of India, using a morphostratigraphic approach generated multi-disciplinary data on Quaternary geological history, besides establishing the presence of prehistoric human cultures in this part of Northeast India. After a gap of some three decades, the present research group with multi-disciplinary backgrounds undertook some extensive geological traverses and archaeological mapping across some of the well-mapped Quaternary fluvial sequences in the intermontane valleys of Khowai and in West Tripura districts to understand the context of the Stone Age sites. The Quaternary deposits significantly host stratified records of prehistoric artefacts made exclusively of petrified fossil woods of Neogene origin. The in-depth survey strengthens our understanding of the vertical and horizontal continuity of the Stone Age materials in certain areas of the Sonai Valley, which appears to be the most widespread prehistoric site covering an area of approx. 0.256 km2. The study opens up vistas for further research on the chronology and cultural affinities with the neighbouring regions of Myanmar and Bangladesh.

In this paper, a new species of fossil wood, Paraperseoxylon septatum sp. nov. (Lauraceae), from the
Cretaceous of Puerto Yeru
a Formation, is described. The fossil wood herein studied has features of the
Lauraceae family, and particularly resembles the extant genus Persea Mill. The possible climatic conditions
of the Puerto Yerúa Formation were inferred using the Vulnerability Index, Mesomorphy ratios and
the Taxon Independent Approach of the anatomical features present in the fossil wood described, suggesting
a warm and humid to seasonally dry context. This material is the first record known from the
Cretaceous of Northeastern Argentina and the earliest occurrence in the Southern Hemisphere of a fossil
taxon with feature closest to Persea, and clearly establishes the presence of Lauraceae in Northeastern
Argentina during the Cretaceous. Nowadays the genus Persea has a tropical and subtropical disjunct
distribution in the Americas, Asia, and the Canary Islands. The present study provides information
pertinent to understanding its phylogenetic context and biogeographic history.

AMS dating of the two wooden objects (a pot and a bracelet) from Early Neolithic contexts from Măgura and Grădinile settlements gave astonishing results corresponding to the Interpleniglacial period. Further analyses and research indicates that the Early Neolithic Starcevo Culture groups from South Romania intentionally searched and used mineralized fossil wood available in river valleys beds from South Carpathian slopes.

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact,
fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah. The Morrison  Formation in northeastern Utah consists of four members. In ascending chronostratigraphic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The lithology (including the presence of glauconite grains) and fossil assemblage of the lower two members (Windy Hill and Tidwell) indicate a marine to marginal marine (coastal plain) depositional environment,  whereas the lithology, fossil flora and fauna assemblage of the upper two members (Salt Wash and Brushy
Basin) indicate a fluvial–lacustrine depositional environment.
At least 10 fossil log sites in Rainbow Draw have been documented so far, and geologic mapping indicates that the logs and wood all occur in the same stratigraphic interval within the Salt Wash Member, approximately 17 to 27 m above the base of the member. The unit containing the logs and wood is about 11 m thick and consists of very fine to fine-grained sandstone and siltstone with indistinct bedding and no discernible sedimentary features. The logs are siliceous, some have a
coaly exterior, and they range in exposed length from 0.5 to 11 m and reach diameters up to 1.1 m. In the Miners Draw area, a single siliceous log is documented in the upper part of the Salt Wash Member within a silty sandstone unit that is 4 m thick; its exposed length is about 6 m. Although the correlation of the Miners Draw log-bearing interval to the interval in Rainbow Draw is uncertain, both units are lithologically similar and both occur in the upper part of the Salt Wash Member. The logs have been identified as araucariaceous conifers that pertain to the same taxon originally described as "Araucarioxylon hoodii" Tidwell et Medlyn 1993 from Mt. Ellen in the Henry Mountains of southern Utah. Concurrent systematic work will prompt a nomenclatural transfer of this
species to the genus "Agathoxylon."
Based on the abundance of large fossil logs and wood in the same stratigraphic interval in Rainbow Draw, we hypothesize that the area was covered by stands of moderately large trees of araucariaceous conifers. The sedimentological evidence suggests that the trees were not transported far from their original site of growth before they were deposited in a low-energy floodplain environment.

—In this contribution, four species of Agathoxylon are described from the La Matilde Formation, Gran Bajo de San Julián and central and southwestern sectors of Santa Cruz Province, Argentina. Agathoxylon agathioides (Kräusel and Jain) n. comb., Agathoxylon santalense (Sah and Jain) n. comb., Agathoxylon termieri (Attims) Gnaedinger and Herbst, and the new species Agathoxylon santacruzense n. sp. are described based on a detailed description of the secondary xylem. In this work, it was possible to construct scatter plots to elucidate the anatomical differences between the fossil species described on quantitative anatomical data. Comparisons are made with other Agathoxylon species from Gondwana. These parameters can be used to discriminate genera and species of wood found in the same formation, as well as to establish differences/similarities between other taxa described in other formations. Some localities contain innumerable " in situ " petrified trees, which allowed us to infer that these taxa formed small forests, or local forests, or small forests within a dense forest, which is a habitat coincident with the extant Araucariaceae.