Pedogeomorphology, geochronology and paleobotany of soil profiles obtained in the Kyichu River catchment, sourthern Tibet

Results of pedogeomorphological, geochronological and paleobotanical investigations are presented covering the last ca. 4,000 years. The study sites are located in the heavily degraded Kyichu River catchment around Lhasa at 3,600-4,600 m a.s.l. Repeatedly, colluvial sediments have been recorded overlying paleosols. These deposits can be divided into i) coarse-grained sediments with a high proportion of stones and boulders originating from alluvial fans and debris flows, ii) matrix supported sediments with some stones and boulders originating from mudflows or combined colluvial processes such as hillwash plus rock fall, and iii) fine-grained sediments originating from hill wash. The IRSL multi-level dating of profile QUG 1 points to a short-time colluvial sedimentation between 1.0 ± 0.1 and 0.8 ± 0.1 ka. In contrast, dated paleosols of profile GAR 1 (7,908 ± 99 and 3,668 ± 57 BP) encompass a first colluvial episode. Here, the upper colluvial sedimentation took place during several periods between 2.6 ± 0.3 and 0.4 ± 0.1 ka. For the first time in Tibet, a systematic extraction, determination and dating of charcoals from buried paleosols was conducted. The charcoals confirm the Late Holocene presence of juniper forests or woodlands in a now treeless, barren environment. A pollen diagram from Lhasa shows a distinct decline of pollen of the Jumperus-type around 4,140 ± 50 BP, which is interpreted as indicating a clearing of forests on the adjacent slopes. It is assumed that the environmental changes from forests to desertic rangelands since ca. 4,000 BP have been at least reinforced by humans.

Pedogeomorphology, geochronology and paleobotany of soil profiles obtained in the Nagqu area, central Tibet

Vast areas on the Tibetan Plateau are covered by alpine sedge mats consisting of different species of the genus Kobresia. These mats have topsoil horizons rich in rhizogenic organic matter which creates turfs. As the turfs have recently been affected by a complex destruction process, knowledge concerning their soil properties, age and pedogenesis are needed. In the core area of Kobresia pygmaea mats around Nagqu (central Tibetan Plateau, ca. 4500 m a.s.l.), four profiles were subjected to pedological, paleobotanical and geochronological analyses concentrating on soil properties, phytogenic composition and dating of the turf. The turf of both dry K. pygmaea sites and wet Kobresia schoenoides sites is characterised by an enrichment of living (dominant portion) and dead root biomass. In terms of humus forms, K. pygmaea turfs can be classified as Rhizomulls mainly developed from Cambisols. Wet-site K. schoenoides turfs, however, can be classified as Rhizo-Hydromors developed from Histic Gleysols. At the dry sites studied, the turnover of soil organic matter is controlled by a non-permafrost cold thermal regime. Below-ground remains from sedges are the most frequent macroremains in the turf. Only a few pollen types of vascular plants occur, predominantly originating from sedges and grasses. Large amounts of microscopic charcoal (indeterminate) are present. Macroremains and pollen extracted from the turfs predominantly have negative AMS 14C ages, giving evidence of a modern turf genesis. Bulk-soil datings from the lowermost part of the turfs have a Late Holocene age comprising the last ca. 2000 years. The development of K. pygmaea turfs was most probably caused by an anthropo(zoo)-genetically initiated growth of sedge mats replacing former grass-dominated vegetation ('steppe'). Thus the turfs result from the transformation of pre-existing topsoils comprising a secondary penetration and accumulation of roots. K. schoenoides turfs, however, are characterised by a combined process of peat formation and penetration/accumulation of roots probably representing a (quasi) natural wetland vegetation.

Patterns in paleobotany : proceedings of a Czech-U.S. carboniferous paleobotany workshop /

Includes bibliographical references.

云南吕合中新世木贼属草问荆比较种及其古生态学研究

位于我国西南边陲的云南省今天以丰富的植物种类、复杂的植被类型，被誉为“绿色明珠”和“植物王国”，其现今格局的形成无疑是长期历史演化的结晶。探讨其植物区系成分的由来、植被演替的规律及其与环境的关系已经成为研究的热点问题。 新生代是云南植物王国形成和环境演变过程中的关键地质时期。本论文以新生代晚第三纪中新世吕合地区植物群为研究的切入点，对其中的木贼属（Equisetum L.）化石做了深入研究。 木贼属为早期陆地维管植物楔叶类唯一的现存代表，过去报道和研究的化石记录多集中在古生代和中生代，新生代的较少。 本文首次报道云南吕合中新世地层中发现的以地下根状茎和块茎形式保存的木贼属草问荆比较种（E. cf. pratense Ehrhart）。化石根状茎分明显的节和节间， 节部簇生1-4 串串珠状的块茎（每串块茎数目2-4 个），单个块茎椭圆形、圆球形、卵形或纺锤形，通常位于串珠末端的块茎顶端较尖。 木贼属现存两亚属：问荆亚属（8 个种，气孔与表皮齐平，地上茎一年生， 通常分枝，孢子囊穗顶端钝）和木贼亚属（7 个种，气孔凹陷于表皮，地上茎宿存，通常不分枝，孢子囊穗顶端尖）。问荆亚属中，除溪木贼（E. fluviatile L.） 和E. bogotense Kunth 外，其余6 个种都有块茎，而从未在木贼亚属中发现过块茎。具块茎的问荆亚属6 个种中，仅发现草问荆有2-3 个串联的块茎，其余种均为单个块茎。鉴于吕合发现的化石根状茎上着生块茎之特征和现代草问荆的情形一致，表明二者之间亲缘相近，故将吕合化石标本鉴定为草问荆比较种。 前人在北美、欧洲和亚洲的早白垩世到第三纪地层中，报道过14 种具根状茎和块茎的木贼类化石，其中具串珠状块茎的仅5 种。这些化石种与吕合标本有明显区别，如美国怀俄明州始新世的E. haydenii Lesquereux 根状茎的节部收缩，块茎有分枝。美国蒙大纳州渐新世至中新世的E. cf. arcticum Heer 和中国吉林始新世的E. hunchunense Guo 块茎在根状茎节上轮生。尽管据报道加拿大白垩纪E. perlaevigatum Cockerell 和辽宁北票早白垩世Equisetites longevaginatus Wu 有串珠状块茎结构，但原文提供的照片显示却只有单个块茎。 根据将今论古的原理，似可将化石的现存最近亲缘种草问荆的生境和物候调查结论，推演到发现草问荆比较种的云南吕合中新世地点及相应层位上。这样，不仅可以推测当时环境湿润，而且化石沉积的时间应为块茎形成的秋冬季节。结合前人在该产地发现喜热的亚热带成分壳斗科青冈属、栲属、金缕梅科枫香属等花粉和喜湿的桦木科桤木属花粉、杉科落羽杉型木以及红杉属的枝叶和球果，表明云南吕合中新世植被类型为常绿落叶阔叶混交林，气候类型为温暖湿润的亚热带气候。

Reconstitution paléo-écologique et contexte magnéto-stratigraphique de la forêt fossile de l'île Bylot (Nunavut)

Ce projet porte sur la reconstitution paléo-écologique d'un environnement forestier fossile retrouvé sur un plateau au sud-ouest de l'île Bylot. Il a comme objectifs 1) de préciser la chrono-stratigraphie du site; 2) d’établir une liste et une succession des différents taxons polliniques retrouvés dans les différentes unités stratigraphiques du site; 3) d’estimer leur âge et 4) d’en inférer des conditions climatiques (température et précipitations). Plusieurs coupes stratigraphiques ont été excavées puis échantillonnées afin de réaliser des analyses stratigraphiques, paléomagnétiques et polliniques. Un GPS différentiel fut également utilisé afin de caractériser à petite et grande échelle les unités stratigraphiques associées aux unités organiques fossiles. Les résultats des analyses granulométriques indiquent la séquence de dépôt suivante au sein d’une dépression dans la roche en place (schiste tertiaire) : 1) un diamicton glaciaire local ; 2) un sédiment limoneux d’origine glacio-lacustre ; 3) une unité organique tourbeuse; 4) une unité de type alluvial ; 5) un sédiment fluvio-glaciaire et 6) un diamicton glaciaire d’origine allochtone. Les analyses polliniques suggèrent une végétation similaire à celle présente près de la limite des arbres actuelle, environ 2000 km plus au sud. Les conditions climatiques plus humides et plus chaudes permettaient notamment la croissance du pin (Pinus type strobus et banksiana), de l’épinette (Picea cf. mariana), de l’aulne (type crispa et incana) et du mélèze (Larix, indifférencié). Enfin, les études paléomagnétiques et la présence d’espèces éteintes suggèrent un âge pour les dépôts organiques fossiles situé entre 2,14 et 2,15 Ma ou entre 2,581 et 3,040 Ma.

Granes per a l' arqueologia [Ressenya de l'article de Buxó i Capdevila, Ramón. Metodología y técnicas para la recuperación de restos vegetales (en especial referéncia a semillas y frutos) en yacimientos arqueológicos. Cahier Noir, núm. 5, 63 p. Girona, 1990]

Ressenya de l'article de Ramón Buxó i Capdevila,'Metodología y técnicas para la recuperación de restos vegetales (en especial referéncia a semillas y frutos) en yacimientos arqueológicos', publicat al número 5 de 'Cahier Noir' l'any 1991. Es reflexiona sobre les disciplines auxiliars de l' Arqueologia

Lower Permian Sphenopsids from Cerquilho, Northeastern Paraná Basin, Brazil

The Lower Permian sphenopsids Phyllotheca australis Brongniart, 1828, Stephanophyllites sanpaulensis Millan & Dolianiti, 1980a and Paracalamites australis Rigby, 1966b, from the Toca do Índio outcrop in Cerquilho Municipality (northeastern Paraná Basin, Tubarō Supergroup) are redescribed on the basis of newly collected specimens. Some aspects, such as the leafsheath opening angles of the whorls and the foliar transverse to oblique striae or wrinkles, are discussed in detail. Phyllotheca australis and Paracalamites australis are widespread in Gondwana and have no particular stratigraphic or phylogenetic value. Otherwise, the genus Stephanophyllites, although only found in the Paraná Basin and probably in Argentina (Bajo de Véliz Formation, close to the Carboniferous-Permian limit), can have a greater importance on account of some Raniganjia-like characters superimposed to a gross Phyllotheca-like morphology.

Esfenóitas do monumento natural das árvores fossilizadas do Tocantins, Bacia do Parnaíba (Permiano, Brasil)

Pós-graduação em Geologia Regional - IGCE

Estudo de marattiales da Floresta Petrificada do Tocantins Setentrional (Permiano, Bacia do Parnaíba)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Paleoecologia e tafonomia da floresta petrificada do Tocantins setentrional (Bacia do Parnaíba, Permiano)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Paleoenvironment and Paleoecology of a Late Paleocene High-Latitude Terrestrial Succession, Arkose Ridge Formation at Box Canyon, Southern Talkeetna Mountains, Alaska

Paleogene sedimentary rocks of the Arkose Ridge Formation (Talkeetna Mountains, Alaska) preserve a record of a fluvial-lacustrine depositional environment and its forested ecosystem in an active basin among the convergent margin tectonic processes that shaped southern Alaska. An -800 m measured succession at Box Canyon indicates braid-plain deposition with predominantly gravelly deposits low in the exposure to sandy and muddy facies associations below an overlying lava flow sequence. U-Pb geochronology on zircons from a tuff and a sandstone within the measured section, as well as an Ar/Ar date from the overlying lava constrain the age of the sedimentary succession to between similar to 59 Ma and 48 Ma Fossil plant remains occur throughout the Arkose Ridge Formation as poorly-preserved coalified woody debris and fragmentary leaf impressions. At Box Canyon, however, a thin la-custrine depositional lens of rhythmically laminated mudrocks yielded fish fossils and a well-preserved floral assemblage including foliage and reproductive organs representing conifers, sphenopsids, monocots, and dicots. Leaf physiognomic methods to estimate paleoclimate were applied to the dicot leaf collection and indicate warm temperate paleotemperatures (-11-15 +/- -4 degrees C MAT) and elevated paleoprecipitation (-120 cm/yr MAP) estimates as compared to modem conditions; results that are parallel with previously published estimates from the partly coeval Chickaloon Formation deposited in more distal depositional environments in the same basin. The low abundance of leaf herbivory in the Box Canyon dicot assemblage (-9% of leaves damaged) is also similar to the results from assemblages in the meander-plain depositional systems of the Chickaloon. This new suite of data informs models of the tectonostratigraphic evolution of southern Alaska and the developing understanding of terrestrial paleoecology and paleoclimate at high latitudes during the Late Paleocene-Early Eocene greenhouse climate phase. (c) 2014 Elsevier B.V. All rights reserved.