Distribution of organic-rich sediments through the Phanerozoic

It is commonly assumed that rates of accumulation of organic-rich strata have varied through geologic time with some periods that were particularly favorable for accumulation of petroleum source rocks or coals. A rigorous analysis of the validity of such an assumption requires consideration of the basic fact that although sedimentary rocks have been lost through geologic time to erosion and metamorphism. Consequently, their present-day global abundance decreases with their geologic age. Measurements of the global abundance of coal-bearing strata suggest that conditions for coal accumulation were exceptionally favorable during the late Carboniferous. Strata of this age constitute 21% of the world's coal-bearing strata. Global rates of coal accumulation appear to have been relatively constant since the end of the Carboniferous, with the exception of the Triassic which contains only 1.75% of the world's coal-bearing strata. Estimation of the global amount of discovered oil by age of the source rock show that 58% of the world's oil has been sourced from Cretaceous or younger strata and 99% from Silurian or younger strata. Although most geologic periods were favourable for oil source-rock accumulation the mid-Permian to mid-Jurassic appears to have been particularly unfavourable accounting for less than 2% of the world's oil. Estimation of the global amount of discovered natural gas by age of the source rock show that 48% of the world's oil has been sourced from Cretaceous or younger strata and 99% from Silurian or younger strata. The Silurian and Late Carboniferous were particularly favourable for gas source-rock accumulation respectively accounting for 12.9% and 6.9% of the world's gas. By contrast, Permian and Triassic source rocks account for only 1.7% of the world's natural gas. Rather than invoking global climatic or oceanic events to explain the relative abundance of organic rich sediments through time, examination of the data suggests the more critical control is tectonic. The majority of coals are associated with foreland basins and the majority of oil-prone source rocks are associated with rifting. The relative abundance of these types of basin through time determines the abundance and location of coals and petroleum source rocks.

Reconstruction of a multi-vent kimberlite eruption from deposit and host rock characteristics: Jericho kimberlite, Nunavut, Canada

The Jericho kimberlite (173.1. ±. 1.3. Ma) is a small (~. 130. ×. 70. m), multi-vent system that preserves products from deep (>. 1. km?) portions of kimberlite vents. Pit mapping, drill core examination, petrographic study, image analysis of olivine crystals (grain size distributions and shape studies), and compositional and mineralogical studies, are used to reconstruct processes from near-surface magma ascent to kimberlite emplacement and alteration. The Jericho kimberlite formed by multiple eruptions through an Archean granodiorite batholith that was overlain by mid-Devonian limestones ~. 1. km in thickness. Kimberlite magma ascended through granodiorite basement by dyke propagation but ascended through limestone, at least in part, by locally brecciating the host rocks. After the first explosive breakthrough to surface, vent deepening and widening occurred by the erosive forces of the waxing phase of the eruption, by gravitationally induced failures as portions of the vent margins slid into the vent and, in the deeper portions of the vent (>. 1. km), by scaling, as thin slabs burst from the walls into the vent. At currently exposed levels, coherent kimberlite (CK) dykes (<. 40. cm thick) are found to the north and south of the vent complex and represent the earliest preserved in-situ products of Jericho magmatism. Timing of CK emplacement on the eastern side of the vent complex is unclear; some thick CK (15-20. m) may have been emplaced after the central vent was formed. Explosive eruptive products are preserved in four partially overlapping vents that are roughly aligned along strike with the coherent kimberlite dyke. The volcaniclastic kimberlite (VK) facies are massive and poorly sorted, with matrix- to clast-supported textures. The VK facies fragmented by dry, volatile-driven processes and were emplaced by eruption column collapse back into the volcanic vents. The first explosive products, poorly preserved because of partial destruction by later eruptions, are found in the central-east vent and were formed by eruption column collapse after the vent was largely cleared of country rock debris. The next active vent was either the north or south vent. Collapse of the eruption column, linked to a vent widening episode, resulted in coeval avalanching of pipe margin walls into the north vent, forming interstratified lenses of country rock-rich boulder breccias in finer-grained volcaniclastic kimberlite. South vent kimberlite has similar characteristics to kimberlite of the north vent and likely formed by similar processes. The final eruptive phase formed olivine-rich and moderately sorted deposits of the central vent. Better sorting is attributed to recycling of kimberlite debris by multiple eruptions through the unconsolidated volcaniclastic pile and associated collapse events. Post-emplacement alteration varies in intensity, but in all cases, has overprinted the primary groundmass and matrix, in CK and VK, respectively. Erosion has since removed all limestone cover.

Geochronological (U–Pb, U–Th–total Pb, Sm–Nd) and geochemical (REE, 87Sr/86Sr, δ18O, δ13C) tracing of intraplate tectonism and associated fluid flow in the Warburton Basin, Australia

The Warburton Basin of central Australia has experienced a complex tectonic and fluid-flow history, resulting in the formation of various authigenic minerals. Geochemical and geochronological analyses were undertaken on vein carbonates from core samples of clastic sediments. Results were then integrated with zircon U–Pb dating and uraninite U–Th–total Pb dating from the underlying granite. Stable and radiogenic isotopes (δ18O, Sr and εNd), as well as trace element data of carbonate veins indicate that >200 °C basinal fluids of evolved meteoric origin circulated through the Warburton Basin. Almost coincidental ages of these carbonates (Sm–Nd; 432 ± 12 Ma) with primary zircon (421 ± 3.8 Ma) and uraninite (407 ± 16 Ma) ages from the granitic intrusion point towards a substantial period of active tectonism and an elevated thermal regime during the mid Silurian. We hypothesise that such a thermal regime may have resulted from extensional tectonism and concomitant magmatic activity following regional orogenesis. This study shows that the combined application of geochemical and geochronological analyses of both primary and secondary species may constrain the timing of tectonomagmatic events and associated fluid flow in intraplate sedimentary basins. Furthermore, this work suggests that the Sm–Nd-isotopic system is surprisingly robust and can record geologically meaningful age data from hydrothermal mineral species.

Triassic eclogite from northern Vietnam: inferences and geological significance

The first finding of low-temperature eclogites from the Indochina region is reported. The eclogites occur along the Song Ma Suture zone in northern Vietnam, which is widely regarded as the boundary between the South China and Indochina cratons. The major lithology of the area is pelitic schist that contains garnet and phengite with or without biotite, chloritoid, staurolite and kyanite, and which encloses blocks and lenses of eclogite and amphibolite. The eclogites commonly consist of garnet, omphacite, phengite, rutile, quartz and/or epidote with secondary barroisite. Omphacite is commonly surrounded by a symplectite of Na-poor omphacite and Na-rich plagioclase. In highly retrograded domains, diopside + tremolite + plagioclase symplectites replace the primary phases. Estimated peak-pressure metamorphic conditions based on isochemical phase diagrams for the eclogites are 2.1-2.2 GPa and 600-620 degrees C, even though thermobarometric results yield higher pressure and temperature conditions (2.6-2.8 GPa and 620-680 degrees C). The eclogites underwent a clockwise P-T trajectory with a post-peak-pressure increase of temperature to a maximum of > 750 degrees C at 1.7 GPa and a subsequent cooling during decompression to 650 degrees C and 1.3 GPa, which was followed by additional cooling before close-to-isothermal decompression to similar to 530 degrees C at 0.5 GPa. The surrounding pelitic schist (garnet-chloritoid-phengite) records similar metamorphic conditions (580-600 degrees C at 1.9-2.3 GPa) and a monazite chemical age of 243 +/- 4 Ma. A few monazite inclusions within garnet and the cores of some zoned monazite in garnet-phengite schist record an older thermal event (424 +/- 15 Ma). The present results indicate that the Indochina craton was deeply (> 70 km) subducted beneath the South China craton in the Triassic. The Silurian cores of monazite grains may relate to an older non-collisional event in the Indochina craton.

Features of the geomagnetic field during the Holocene and Proterozoic

The geomagnetic field is one of the most fundamental geophysical properties of the Earth and has significantly contributed to our understanding of the internal structure of the Earth and its evolution. Paleomagnetic and paleointensity data have been crucial in shaping concepts like continental drift, magnetic reversals, as well as estimating the time when the Earth's core and associated geodynamo processes begun. The work of this dissertation is based on reliable Proterozoic and Holocene geomagnetic field intensity data obtained from rocks and archeological artifacts. New archeomagnetic field intensity results are presented for Finland, Estonia, Bulgaria, Italy and Switzerland. The data were obtained using sophisticated laboratory setups as well as various reliability checks and corrections. Inter-laboratory comparisons between three laboratories (Helsinki, Sofia and Liverpool) were performed in order to check the reliability of different paleointensity methods. The new intensity results fill up considerable gaps in the master curves for each region investigated. In order to interpret the paleointensity data of the Holocene period, a novel and user-friendly database (GEOMAGIA50) was constructed. This provided a new tool to independently test the reliability of various techniques and materials used in paleointensity determinations. The results show that archeological artifacts, if well fired, are the most suitable materials. Also lavas yield reliable paleointensity results, although they appear more scattered. This study also shows that reliable estimates are obtained using the Thellier methodology (and its modifications) with reliability checks. Global paleointensity curves during Paleozoic and Proterozoic have several time gaps with few or no intensity data. To define the global intensity behavior of the Earth's magnetic field during these times new rock types (meteorite impact rocks) were investigated. Two case histories are presented. The Ilyinets (Ukraine) impact melt rocks yielded a reliable paleointensity value at 440 Ma (Silurian), whereas the results from Jänisjärvi impact melts (Russian Karelia, ca. 700 Ma) might be biased towards high intensity values because of non-ideal magnetic mineralogy. The features of the geomagnetic field at 1.1 Ga are not well defined due to problems related to reversal asymmetries observed in Keweenawan data of the Lake Superior region. In this work new paleomagnetic, paleosecular variation and paleointensity results are reported from coeval diabases from Central Arizona and help understanding the asymmetry. The results confirm the earlier preliminary observations that the asymmetry is larger in Arizona than in Lake Superior area. Two of the mechanisms proposed to explain the asymmetry remain plausible: the plate motion and the non-dipole influence.

The geochronology of the plutonic and metamorphic rocks of New Zealand

Extensive Rubidium-Strontium age determinations on both mineral and total rock samples of the crystalline rocks of New Zealand, which almost solely crop out in the South Island, indicate widespread plutonic and metamorphic activity occurred during two periods, one about 100-118 million years ago and the other about 340-370 million years ago. The former results date the Rangitata Orogeny as Cretaceous. They associate extensive plutonic activity with this orogeny which uplifted and metamorphosed the rocks of the New Zealand Geosyncline, although no field association between the metamorphosed geosynclinal rocks and plutonic rocks has been found. The Cretaceous plutonic rocks occur to the west in the Foreland Province in Fiordland, Nelson, and Westland, geographically separated from the Geosynclinal Province. Because of this synchronous timing of plutonic and high pressure metamorphic activity in spatially separated belts, the Rangitata Orogeny in New Zealand is very similar to late Mesozoic orogenic activity in many other areas of the circum-Pacific margin (Miyashiro, 1961).

The 340-370 million year rocks, both plutonic and metamorphic, have been found only in that part of the Foreland Province north of the Alpine Fault. There, they are concentrated along the west coast over a distance of 500 km, and appear scattered inland from the coast. Probably this activity marks the outstanding Phanerozoic stratigraphic gap in New Zealand which occurred after the Lower Devonian.

A few crystalline rocks in the Foreland Province north of the Alpine Fault with measured ages intermediate between 340 and 120 million years have been found. Of these, those with more than one mineral examined give discordant results. All of these rocks are tentatively regarded as 340-370 million year old rocks that have been variously disturbed during the Rangitata Orogeny, 100-120 million years ago.

In addition to these two periods, plutonic activity, dominantly basic and ultrabasic, but including the development of some rocks of intermediate and acidic composition, occurred along the margin of the Geosynclinal Province at its border with the Foreland Province during Permian times about 245 million years ago, and this activity possibly extended into the Mesozoic.

Evidence from rubidium-strontium analyses of minerals and a total rock, and from uranium, thorium, and lead analyses of uniform euhedral zircons from a meta-igneous portion of the Charleston Gneiss, previously mapped as Precambrian, indicate that this rock is a 350-370 million year old plutonic rock metamorphosed 100 million yea rs ago during the Rangitata Orogeny. No crystalline rocks with primary Precambrian ages have been found in New Zealand. However, Pb²⁰⁷/Pb₂₀₆ ages of 1360 million years and 1370 million years have been determined for rounded detrital zircons separated from each of two hornfels samples of one of New Zealand's olde st sedimentary units, the Greenland Series. These two samples were metamorphosed 345- 370 million years ago. They occur along the west coast, north of the Alpine Fault, at Waitaha River and Moeraki River, separated by 135 km. The Precambrian measured ages are most likely minimum ages for the oldest source area which provided the detrital zircons because the uranium, thorium and lead data are highly discordant. These results are of fundamental importance for the tectonic picture of the Southwest Pacific margin and demonstrate the existence of relatively old continental crust of some lateral extent in the neighborhood of New Zealand.

Mapeamento sísmico de intrusões ígneas na bacia do Amazonas e suas implicações para um modelo não-convencional de geração de hidrocarbonetos

A maioria das bacias paleozóicas brasileiras apresenta matéria orgânica termicamente pouco evoluída nos intervalos correspondentes ao Devoniano. O modelo mais adequado para se entender a geração, migração e acumulação de HC estaria relacionado às fases de intrusão de diabásio. No caso da Bacia do Amazonas, embora tenha havido condições de soterramento suficientes para a geração de hidrocarbonetos, não se deve descartar o modelo não convencional de geração como uma das formas possíveis de dar origem as acumulações comerciais de óleo e gás. Acredita-se que o intervalo mais apropriado para a geração de hidrocarbonetos (HC) inclua apenas as rochas depositadas no intervalo Frasniano, embora as rochas associadas ao intervalo Llandoveriano, também, devam ser observadas com atenção. Com o intuito de compreender melhor o papel da atividade magmática na evolução da Bacia do Amazonas, foi realizado o mapeamento sísmico de soleiras de diabásio e análise de dados geoquímicos de pirólise Rock-Eval e COT. Assim, foi possível avaliar a geração/migração de hidrocarbonetos e a variação dos parâmetros geotérmicos na Bacia do Amazonas, causados pela intrusão das soleiras de diabásio. A análise sismoestratigráfica baseou-se na interpretação de 20 linhas sísmicas 2D pós-stack, na qual foram reconhecidos e mapeados horizontes sísmicos (topos de formações e corpos ígneos intrusivos), utilizando dados de poços e dados da literatura para correlação. As intrusões de soleiras estão presentes nas sucessões de folhelhos/siltitos e anidritas das formações Andirá e Nova Olinda, respectivamente. Observou-se que as soleiras de diabásio podem estar intimamente relacionadas a diques sistematicamente orientados, tendo estes diques a função de alimentadores das soleiras. Extensas soleiras planares com segmentos transgressivos ocorrem nos níveis estratigráficos mais rasos da Bacia do Amazonas, e em maiores volumes nas formações Andirá e Nova Olinda. Em algumas regiões as soleiras desenvolvem morfologias marcantes em forma de pires. Esses corpos possuem espessuras que podem chegar a 500m. Comumente, a geometria em lençol denotada pelo paralelismo dos refletores está presente em toda extensão do mapeamento da bacia. Também foram observadas estruturas em domo. O efeito térmico imposto pelas intrusões dos corpos ígneos, diques e soleiras foi de grande importância, pois sem ele não haveria calor para a transformação da matéria orgânica. Através da análise de pirólise Rock-Eval e teor de carbono orgânico, foi possível avaliar e correlacionar os parâmetros como S2 (potencial de geração), IH (índice de hidrogênio), S1 (hidrocarbonetos livres) e Tmax (evolução térmica) com a profundidade. Foram utilizados dados de 04 poços na qual dois deles foram compilados a partir de artigos e teses publicados. As rochas potencialmente geradoras de petróleo são aquelas que apresentam COT igual ou superior a 1%. Dos quatro poços analisados, dois deles apresentam COT > 1% para a Formação Barreirinhas, mostrando que as rochas sedimentares são potencialmente geradoras de HC. Altos valores Tmax podem ser justificados pelo efeito térmico causado por intrusões de diabásio. Os resultados de índice de hidrogênio (IH) apresentaram valores abaixo de 200mgHC/g COT, indicando o potencial gerador desta bacia para gás.

Revisão do Ramo Gondwânico da família Mawsoniidae (Sarcopterygii: Actinistia: Coelacanthiformes)

Representados aualmente por apenas duas espécies: Latimeria chalumnae e L. menadoensis, os celacantos (Infraordem Actinistia) já foi muito mais numeroso, prolífico desde os tempos de seu surgimento no Devoniano Inferior. Dentro de Actinistia a família Mawsoniidae se destaca por abranger as maiores espécies do grupo, algumas atingindo até três metros de comprimento. A entrada de Mawsoniidae no continente Gondwana se deu durante o Jurássico superior, período o qual é atribuído a espécie Parnaibaia maranhoensis da bacia do Parnaíba (Maranhão). No cretáceo a família se ramificou em dois outros gêneros Mawsonia (com conhecidas ocorrências brasileiras e africanas) e Axelrodichthys (gênero brasileiro com alguns indícios de presença na África). Este trabalho teve por objetivo realizar uma redescrição e comparação de seis espécies do ramo gondwânico da família Mawsoniidae: Parnaibaia maranhoensis, Axelrodichthys araripensis, Mawsonia gigas, M. minor, M. lavocati e M. brasiliensis. Os espécimes estão depositados em oito instituições: três nacionais e cinco internacionais. Após uma criteriosa descrição anatômica dos exemplares caracteres foram selecionados para a realização de uma análise filogenética restrita ao grupo. Os resultados das observações anatômicas revelaram diversas estruturas ainda não descritas na literatura, incluindo o primeiro elemento medial do esqueleto apendicular de Mawsoniidae a ser observado, além de diversas diferenças e afinidades entre as seis espécies. P. maranhoensis apresentou um conjunto de caracteres plesiomórfico que foram interpretados como sendo o resultado de um evento de neotenia, algo inédito na literatura de celacantos. Todas as espécies do gênero Mawsonia apresentaram características diagnósticas que validam sua separação em espécies distintas. A análise filogenética resultou em duas árvores igualmente parcimoniosas. Ambas concordam com a posição de Parnaibaia na base do grupo. Mas diferem com relação à posição de A. araripensis e as espécies do gênero Mawsonia. Conclui-se que Parnaibaia é o gênero mais plesiomórfico do grupo, estando na base do ramo gondwânico da família. Axelrodichthys representa a ligação deste com as demais espécies do gênero.

Geoquímica orgânica das Formações Ererê, Barreirinha e Curiri (meso e neo devoniano) em dois poços na porção oeste da bacia do Amazonas

O estudo geoquímico detalhado em dois poços (A e B) na porção oeste da Bacia do Amazonas visou o entendimento da quantidade, fonte e evolução térmica da matéria orgânica presente nas Formações Ererê, Barreirinha e Curiri. Foram efetuadas análises de Carbono Orgânico Total (COT), pirólise Rock-Eval e biomarcadores. Os teores de carbono orgânico total da Formação Barreirinha (Membro Abacaxis) que variam de 1,43% a 8,39%, indicaram que este intervalo possui quantidade de matéria orgânica necessária para ser considerado potencialmente gerador de óleo e gás. As outras unidades litoestratigráficas apresentaram teores de COT pouco significativos. Com base nos dados de pirólise, identificou-se que o intervalo com o melhor potencial gerador corresponde ao Membro Abacaxis. Esta seção no poço A possui índice de hidrogênio (IH) ligeiramente superior a 200 mg HC/gCOT e um potencial gerador (S2)variando de 4 a 17,76 mg de HC/g de rocha, indicando um bom à excelente potencial adequado à geração de gás e condensado. Já no poço B, em decorrência do aumento da evolução térmica, os valores de S2 e IH são mais baixos(variando de 5 a 10 mgHC/g de rocha e com valores entre 50 e 150 mg HC/gCOT, respectivamente), apenas indicando um bom potencial à geração de gás. Segundo diagrama tipo Van Krevlen, a matéria orgânica deste intervalo é heterogênea e se comporta como querogênio tipo II e III no poço A e do tipo III e IV no poço B. As características dos biomarcadores encontrados no Membro Abacaxis indicam uma origem algal e ambiente marinho. O Membro Urariá e a Formação Curiri apresentam indicadores sugestivos de aporte de matéria orgânica de origem terrestre, sendo que o Membro Urariá ainda mostra algumas assinaturas semelhantes com o Membro Abacaxis. Devido a baixa concentração dos biomarcadores cíclicos nas amostras do Poço B, não foi possível realizar uma caracterização da fonte da matéria orgânica da Formação Ererê. A avaliação dos parâmetros utilizados para a interpretação da evolução térmica, como Tmax, taxa de transformação (TT), índice de produção (IP), reflectância da vitrinita calculada (Roc) e razões entre alcanos lineares e ramificados (P/nC17 e F/nC18), indicaram que no intervalo gerador do Poço A houve geração de hidrocarbonetos, mas ainda não correu a migração. No caso do Poço B, os dados mostram que neste intervalo já houve geração e migração de hidrocarbonetos.

Caracterização de reservatórios não convencionais Shale Gas na Formação Barreirinha Bacia do Amazonas

Os folhelhos pretos devonianos da Formação Barreirinha caracterizamse pela alta radioatividade na porção basal, grande extensão areal, espessura e profundidade de soterramento variável que vão de exposição na superfície até mais de 3000 m. Eles são as principais rochas geradoras do sistema petrolífero convencional da Bacia do Amazonas, e recentemente foram consideradas como promissores plays de gás não convencional. Folhelhos são geralmente caracterizados por uma matriz fechada, que faz com que sejam relativamente impermeáveis em relação ao fluxo de gás, a menos que ocorram fraturas, e dependendo das suas características geológicas e geoquímicas podem funcionar com um Sistema Petrolífero autossuficiente, atuando tanto como rocha fonte, quanto como reservatório de gás (reservatório Shale Gas). Assim, o gás natural termogênico ou biogênico gerado pode ser armazenado em folhelhos ricos em matéria orgânica na forma livre, adsorvida, ou em estado dissolvido. Em contraste com os sistemas petrolíferos convencionais, reservatórios Shale Gas, possuem mecanismos de aprisionamento e armazenamento únicos, sendo necessária a utilização de técnicas de avaliações específicas. No entanto, folhelhos prolíficos geralmente podem ser reconhecidos a partir de alguns parâmetros básicos: arquitetura geológica e sedimentar, propriedades geoquímicas e petrofísicas e composição mineralógica. Tendo em vista a carência de pesquisas de caráter descritivo, com cunho exploratório dos folhelhos geradores da Formação Barreirinha, esta dissertação tem como objetivo introduzir uma metodologia de identificação de intervalos de folhelho gerador com potencial para reservatório Shale Gas. Começando com uma investigação regional sobre o contexto geológico e sedimentar, seguido de uma avaliação abrangente enfocando as características geoquímicas, petrofísicas e litofácies dos folhelhos a partir da integração de parâmetros obtidos de perfis geofísicos de poço, análises geoquímicas e aplicação dos conceitos de Estratigrafia de Sequencia.

华南泥盆纪植物原蕨属的发现和原真蕨亚纲的研究

本文详细研究在我国华南泥盆系地层中发现的一种新的原真蕨植物—原蕨属（新属）propterophyton gen. nov.并详细探讨原真蕨植物的分类问题。 原真蕨植物在早期陆地维管植物系统发育中占有十分重要的地位。它是处于原始的裸蕨植物和进步的真蕨植物之间的一种过渡类型，兼具这两类植物的主要特征。 原始蕨植物的研究已有几十年的历史。但往往由于化石材料的奇缺和破碎，限制人们对它的正确认识，因而研究工作的进展一直十分缓慢。近二十多年来，一方面随着原裸子植物的确认和原裸子植物纲（progymospermopsida）的建立，一些所谓的原真蕨植物经研究后被转移到这个新钢里。另一方面，特别是近十年来，世界各国尤其是欧美的古植物学家对新发现的不少珍贵的原真蕨植物化石进行了深入研究，而使人们对这类灭绝植物的认识得以深化，并就它的分类问题，古植物学家不断提出新的见解。 在我国首次发现的原蕨属的标本十分丰富，保存完整。经过深入细致的研究，使我们对这种植物的外部形态和内部结构有了较全面的认识。并由此涉及到对整个原真蕨植物的认识得以进一步的完善，从而提出一个有关原真蕨植物的新概念。在此研究的基础上，综合国际植物学界人士近二十多年来对原真蕨植物研究的资料，本文拟把原真蕨植物归入原真蕨亚纲（primofilices）置于真蕨纲（Filicopsida）之下，与真蕨亚纲（Filices）并列。 大部分原蕨属的标本采自湖北省汉阳县米粮山采石场。化石层位于上泥盆统珞珈山群的下部，距该群底界与下伏中志留统地层之间的假整合面大约有9米。该层为—巨大的粘土岩透镜体，夹在厚至巨厚层的石英砂岩中。依据分散孢子组合的资料，这种植物的地质时代不会晚于晚泥盆世早期，即弗拉斯期（Frasnian）。另有一部分标本则采自湖南市长沙县跳马涧。其时代大约是中泥盆世晚期，即吉维特期（Givetian）。 原蕨属的化石主要保存为炭化的压型标本，部分黄铁矿化。这些标本经过精心修整，采用多种技术处理，并运用扫描电子显微镜观察，显示出了这种植物主要的外部形态和内部组织的特性。 泥盆原蕨（proptrophyton devonicum sp. Nov.）由根状茎、蕨叶和不定根三部分组成。根状茎横生地下，以细而少分枝的不定根固着于土壤中。蕨叶中仅有一枚直接由根状茎顶部生出，余为侧生，以螺旋排列为主。蕨叶由三次羽状分枝的枝系组成，单轴，不具叶片。成对的羽片在叶轴两侧互生。小羽片也以同样的方式成对互生在羽轴两侧。从而形成一种立体生长的四列式蕨叶。小羽片多为六次等二岐式分枝，没有蹼化。生殖小羽片顶部生出成对孢子囊。估计每枚小羽片上可以生长六十四个孢子囊。幼小的孢子囊圆至纺锤形，下垂。成熟的孢子囊弯眉形，直立。两个孢子囊在小羽片顶部排列成山羊角状。四个孢子囊成两对着生，形成一束。孢子囊沿囊壁内面纵裂，不具环带。孢子同型，具三裂缝。蕨叶具轴有两侧对称的维管结构：两个椭圆柱状的维管束在一侧相连，形成一个v字型结构。在维管束的另一侧具有原生木质部腔（lacuna）。后生木质部管胞放射状相连，具有梯形，椭圆形至圆形的具缘纹孔。成对的小羽片迹由两个维管束不相连的一侧交互产生。皮层分为具薄壁组织的外层和具后角组织的内层。表皮上的气孔器很小，散生，气孔与轴行，无副卫细胞。 泥盆原蕨的蕨叶由不具叶片的枝系组成，立体方式生长。小羽片等二岐式分枝。根状茎顶部直接生长一枚蕨叶。孢子囊定生，纵向开裂。这些属于裸蕨植物的原始性状，明显地不同于真蕨植物。但根、茎、叶的初步分化、蕨叶的单轴生长和羽片在叶轴两侧排列以及与之相对应的蕨叶轴内两侧对称的维管结构，表明泥盆原蕨已部分发展到真蕨植物的水平。由此可见，原蕨属即具有裸蕨植物的原始性状，又具有真蕨植物的进步性状，属于一种典型的原真蕨植物。 综合原蕨属及其它原真蕨植物如指蕨属（pseudosporochnus）,羽裂蕨属（Rhacophyton）和十字蕨属（Stauropteris）的特征，归纳出原真蕨植物的孢子体具有以下主要性状：（1）植物体由茎、蕨叶和不定根组成。（2）茎直立或匍伏生长，具放射状对称的内部结构。（3）不定根自茎生出，有的也从叶柄或叶轴生出。（4）蕨叶由完整的羽状分枝的枝系组成。由此形成的蕨叶与枝系在形态上的差异不甚明显。（5）蕨叶单轴式生长，一次多次羽状，呈背腹状或至少叶轴具备背腹性。（6）羽片和小羽片成对的或单个的侧生在轴两侧，形成立体或平面生长的蕨叶。（7）小羽片等二岐式分枝，不具叶片。（8）叶轴和羽轴具两侧对称的，中始式的维管结构。（9）孢子囊远端位着生，无环带，具简单的开裂机制。(10)孢子多为同形，稀有大小两种。简言之，原真蕨植物是一类蕨叶由羽状枝系组成，不具叶片和孢子囊不具环带的原始的真蕨植物。 这种原真蕨植物的新概念为原真蕨植物的分类和蕨叶的起源提供新的解释。 裸蕨植物与原真蕨植物的主要区别，在于后者已经出现根、茎、叶的初步分化，在系统发育中达到一个新的演化水平。但是，原真蕨植物的蕨叶仅由枝系组成，还没有形成叶片，孢子囊叶不具环带，这些特征在系统发育中又低于真蕨植物所达到的一般水平。因此，有无蕨叶叶片和孢子囊有无环带作为区分原真蕨植物和真蕨植物的主要标志。原真蕨植物应以蕨叶未形成叶片和孢子囊不具环带为特征。而真蕨植物则至少应以有叶片的蕨叶或孢子囊具环带为特征。 原真蕨植物，原裸子植物和原始楔叶植物都起源于裸蕨植物，是共同生活在泥盆，演化水平彼此接近的三大分类群。它们之间的区别主要在于叶器官和生殖器官的不同。这里又涉及到蕨叶起源的问题。 历史人们认为蕨叶（复合叶）起源于一个等二岐式分枝的侧枝。但根据已发现的化石资料，特别是原蕨属所表现的性状，蕨叶可能直接起源于具有完整的至少一次羽状分枝枝系的植物。枝系的扁化和蹼化则发生在以后的演化过程中，逐步形成具叶片的枝状复合蕨叶。而仅仅由一个等二岐式分枝的侧枝起源的叶则应归属于简单的枝状叶。本文所讨论的原裸蕨子植物和原始楔叶植物的叶，就是在茎上螺旋排列或轮生的单叶。在蕨叶中，只有小羽片才是由等二岐式分枝的侧枝起源，排列在羽轴两侧。因此，在系统发育中，原裸子植物和原始楔叶植物的茎及其着生的单叶与原真蕨植物的复合蕨叶是同源的。而单叶则与小羽片同源。 根据上述对原真蕨植物的概念和蕨叶及单叶起源的观点，结合化石植物形态学和解剖学两方面的性状，特别是以生殖器官的性状作为分类的依据，纵观几十年来原真蕨植物的分类，大致经历了三个时期。 第一个阶段于本世纪六十年代以前。这个时期的原真蕨植物的分类，受材料限制，研究的程度不够深入，基本上仅以解剖性状作为分类的主要依据。这一时期归属原真蕨植物的“蕨状植物”包括原始蕨类（protopterids）,枝木类（cladoxylaeans）和合生蕨类（coenopterids）这实际上是一个庞杂的类群，包括了后来分出的原裸子植物，原始楔叶植物以及真蕨植物。 第三个阶段从六十年代至七十年代末。由于美国 C. B. Beck博士的重大发现和深入研究的结果，不仅确立了原裸子植物是一类处于裸蕨植物和裸子植物之间的过渡类型，而且为古植物学的研究提供了很好的范例。即化石植物的正确分类也必须依据形态学和解剖学两方面的证据。生活在中泥盆世至晚泥盆世的原裸子植物既有原始维管植物自由孢子生殖的特征，又具有裸子植物木材的组织特征，即次生木质部的管胞具有典型的松柏类的圆形具缘纹孔。一些所谓的“蕨状植物”经过细致地研究被证实应属于原裸子植物，从而被转移到原裸子植物纲内。 六十年代中期，比利时古植物学家 S. Leclercq 和西德古植物学家H. J. Schweitzer 发现芦形木（Cala-mophyton）的维管结构为枝木形。因而将原来归属于原始楔叶植物叉叶目（Hyeniales）的芦形木和叉叶（Hyenia）转移到枝木目中，作为蕨状植物看待。对此，国际古植物学界尚有不同的看法。主要是由于这两种植物的生殖器官业已分化为原始的孢子囊梗，而且单叶的排列也由螺旋着生演化到假轮生的水平。 在此期间，合生蕨植物的自然分类的问题日趋被人重视。 第三个阶段开始于本世纪八十年代。这个时期有关原真蕨植物分类的核心问题。是如何确定芦形木等属的正确的分类位置和如何对合生蕨植物进行更接近于自然的分类。 枝木目(Cladoxylales）目1 9 2 7年建立以来，主要包含了一些生活在早石炭世的植物。这些植物的轴具有多维管束的组织结构。而植物体的整体形态不详。归入此目的有具枝木型维管结构的中泥盆植物指蕨，帚枝木(Cladoxylon scoparium )和芦形木都显示出相似的掌状分枝的外形．但是指蕨的叶为羽状蕨叶，小羽片两侧排列，孢子囊纺锤形，成对顶生，纵向开裂。而帚枝木和芦形术的叶为螺旋排列在茎上的单叶。芦形木的孢子囊已形成了雏形孢囊梗。帚枝木的生殖器官最初被认为是扇状深裂叶具边缘着生的孢子囊。但是1 9 8 0年Scheitger 和Giestn重新研究后，发现它的生殖结构类似芦形木，为原始的孢子囊梗。帚枝木，芦形木和叉叶的单叶与原其蕨植物的蕨叶不仅形态上截然不问，而且在排列上已趋向于轮生。与此同时，孢子囊梗已初步形成。这些性状表明这些植物与楔叶植物有密切的亲缘关系。本文不仅赞同J．E．Skog 及L. P. Banks （1973年）和W．N. Stevart （1983年）将芦形木和叉叶仍归回原始楔叶植物叉叶目，而且将蒂枝木也归入同—个目内。另外，指蕨属根据蕨叶和孢子囊的性状应属于原真蕨植物。到此为止，枝木目（狭义的）只包括具有多维管束的硅化轴的器官属，其分类位置不明。 合生蕨目（Coenopteridales)历来被认为是原真蕨植物的主要代表。过去对这类植物的认识主要建立在解剖材料上，特别是依据叶轴维管结构的形态。在某种程度上，这个目也是一个庞杂的类群。随着合生蕨的生殖结构的不断发现，人们对这类植物的分类，逐渐转移到以孢子囊的性状作为主要的分类依据。本文赞同根据孢子囊的结构，特别是依据环带的形态结构，把该目中的五个科Botryoptoridaceae, Anacboropteridaceae,　Sermaytaceae, Tedeleacoae 和 Psallxochlaenacoae转移到真蕨亚纲的真蕨目(Filicales ）内。另外本文还对比了该目中的孪生蕨科（Zygopteridaceae )的几个属的囊群，孢子囊及环带的性状与莲座目(Marattiales )中莲座科的一个化石属和一个现代属（Angiopteris ）的生殖器官的性状。根据它们之间的相似程度，建议将孪生蕨科移至莲座目。Iridopterids曾被认为是合生蕨植物。根据新的研究资料， lridopterids 与原始楔叶植物的关系比与其它植物的关系更为密切。合生蕨植物中的羽裂蕨属和十字蕨属因蕨叶不具叶片和孢子囊不具环带，似应归入原真蕨亚纲，置于各目的目下。至此为止，合生蕨植物分别归属不同类群而使该目趋于解体。 原真蕨亚纲包括四个目(指蕨目Pseudosporochnales，原蕨目Propterophytales，羽裂蕨目Rhacophytales，十字蕨目Stauropteridales)六个属( Pseudosporochrmus, Propterophyton, Rhacophyton，Protocaphalopteris, Chlidanophyton, Stauropteris) 代表两条演化路线。指蕨目独自代表一条路线。蕨叶为两度空间生长的二列式蕨叶，即单个羽片侧生在叶轴上，与现代蕨叶相似。但与现代真蕨植物之间的演化关系不详。原厥目，羽裂蕨目和十字蕨目代表另一条路线。蕨叶为立体的四列式蕨叶，即成对的羽片侧生在叶轴上。在后一条演化路线中，原蕨目处于较原始的水平。原蕨属可能直接起源于一种与裸蕨植物Pertica 相近似的祖先。羽裂蕨目较为进化。而十字蕨目则达到极为特化，即蕨叶高度简化，出现异形孢子的水平。真蕨亚纲的祖先植物可能自后一条路线中产生。

湖北中泥盆世一植物新属的研究

植物自晚志留世登陆以来，经过对恶劣的陆生环境长期而艰难的适应，在泥盆纪，特别是中上泥盆世开始其大规模的演化发展。在此其间，石松类、楔叶类、前蕨类、真蕨类以及前裸子植物等相继出现，使得陆生植物进入其第一个空前繁盛时期。 但是，也正是在这个介于陆地植物起源及其大规模发展的阶段，植物分类以及各植物之间的亲缘关系很不清楚。特别是前蕨类，它起源于三枝蕨类，并且被认为是真蕨类和前裸子植物的祖先，但目前对它是如何从三枝蕨类进化到真蕨类和前裸子植物却几乎一无所知。就如同一个黑匣子，有一个入口和两个出口，我们的任务就是打开这个黑匣子，弄清楚前蕨类中各植物的自然分类位置以及他们之间的亲缘关系。那么，有关早期陆地植物进化的一些悬而未决的问题也便迎刃而解了。 本论文正是为此目的而作。并且，植物新属变枝蕨的发现将无疑为最终达到这个目的做出很大的贡献。

中国晚泥盆世两种木本石松植物的研究

木本石松植物在晚古生代植物群中一直引人注目，它们是最早在中、晚泥盆世发展乔木和异孢习性的陆生维管植物谱系之一。在这篇报告中，中国两种晚泥盆世（距今约354-370百万年）的木本石松植物被详细地研究了。这两项研究增进了我们对泥盆纪木本石松植物的进化发育生物学的认识。 作者从中国西北部新疆准噶尔盆地上泥盆统的地层中描述了一个新种新疆鳞孢穗Lepidostrobus xinjiangensis sp.nov.，它为我们研究晚泥盆世石松植物的生殖分化和系统发育关系提供了新的认识。这个孢子叶球不同于任何草本石松植物的生殖器官，而与木本石松植物的生殖器官更为相似，它符合鳞孢穗属Lepidostrobus的鉴别性状。它的每个孢子叶由一个楔形的叶柄和一个三角形的叶片构成。孢子叶水平地着生在穗轴上，呈低角度的螺旋排列。叶柄具有侧翼和一个远轴面的脊，其远端延伸为一个上翻的叶片和一个下翻的踵，形成了一种盾状的外貌。孢子囊呈辐向加长、背腹扁的卵球形，具有顶端的纵向开裂。每个孢子囊基部纵向着生在叶柄的近轴面上。在孢子囊中发现了一个柱状的亚孢原组织垫。一个可能的叶舌出现在叶柄近轴面靠孢子囊远端。这个生殖器官是一个小孢子叶球，含石松孢Lycospora型孢子，具有粒状纹饰和赤道凸缘。基于这个鳞孢穗新种，木本石松植物从泥盆纪到石炭纪以来的生殖分化和演化式样在一个系统发育的框架中被讨论了。作者提出，木本石松植物由两性孢子叶球和单孢子叶球所代表的生殖策略到了晚泥盆世已经发展得相当完备，这暗示着系统发育上生有鳞孢穗孢子叶球的木本石松植物比过去所认为得起源要早。 作者重新调查了一个过去描述于中国湖北晚泥盆世（弗拉斯期）黄家磴组地层中的斜方薄皮木Leptophloeum thombicum的树干，并提出关于这个木本石松植物生长结构的新观点。这个树干保存为压扁的硅化化石，具有不均匀渗矿化的初生维管组织和螺旋排列的斜方形叶座。叶座特征符合晚泥盆世广泛分布的植物斜方薄皮木Leptophloeum rhombicum Dawson的鉴别性状。分类上，斜方薄皮木被归入薄皮木科Leptophloeaceae和广义水韭目Isoetales s.l.。这个树干在不同水平的解剖特征证明，斜方薄皮木的个体发育可能符合一种有限的生长方式。结合过去的资料和当前的生长结构分析，作者提出斜方薄皮木具有假单轴分枝的习性，而不是过去所认为的那样长着等二叉分枝的树冠。作者重新复原了这个植物的总体生长形态，它由一个根座式根状茎、一个主干和侧枝三类主要的生长结构单元构成。当这些结果组合了近期的系统发育工作后，它表明斜方薄皮木已经发育了与一些晚泥盆世法门期和石炭纪木本石松植物相似的生长结构，可能代表了早期水韭目植物祖先的生长结构类型之一。

陆地植物对环境变化的响应

陆地植物起源以后，地球上的环境发生了巨大的变化。大气CO2浓度自泥盆纪早期的2000-4OOOμml•mol_1下降至石炭一二叠纪的300μml•mol_1左右，02浓度在泥盆纪至石炭一二叠纪时期，由20-30μml•mol_1上升到70-80μml•mol_1，随后又下降到目前的水平。陆地植物登陆后，形态结构也发生了显著的改变，气生部分表而分化出了通气结构--气孔器和保护结构--角质层。泥盆纪首选标志植物刺镰蕨（Drelpanophycus spinaefrmis）在整个泥盆纪，广布全世界。刺镰蕨的气孔器类型一直存在两种观点，一种认为刺镰蕨的气孔器是平列型，即气孔器山两个保卫细胞和两个副卫细胞组成：另一观点认为刺镰蕨的气孔器为不规则型，即气孔器仅有两个保卫细胞构成，不具副卫细胞。我们借助于扫描电镜、石蜡制片技术和叶表皮离析法，细致地研究了现代石松（Lycopodium japonicum）叶的横切而、表皮及气孔器的内外表面结构，并同刺镰蕨的表皮和气孔器进行了对比。认为刺镰蕨的气孔器和所有的化石石松类及现代石松类的气孔器一样，均属于不规则型。从而解决了关于刺镰蕨气孔器类型的长期争论的关键性科学问题。 胡桃科青钱柳属植物起源于晚白垩世的环北太平洋沿岸，化石植物最早发现于北美古新世和早始新世的Motana,，Wyoming，North Dakota，north Colorado地区，欧亚地区仅出现在渐新世至上新世的Kazakhstan、Germany、Romnania、Russia、Japan、中国云南远谋和四川米易地区。我们将采于吉林省珲春组始新世的叶化石鉴定为一青钱柳相似种，该化石成为东亚地区出现最早的青钱柳属植物，这一发现也支持晚白垩至早第三纪时期环北太平洋两岸曾经相连的观点，青钱柳属在晚白垩由北美起源，在始新世经东亚向欧亚大陆扩散，由于环境变迁，第四纪以后，青钱柳属仪剩一种植物分布于中国的亚热带地区。文中还利用共存分析方法估测出始新世吉林省珲春地区属于暖温带至亚热带气候。 统万城遗址位于我国黄土高原向毛乌素沙漠过渡地带的北缘，属于暖温带森林草原向温带干草原、温带荒漠草原过渡的地区，同时又是东部季风区向西北干旱区过渡的生态环境敏感带。今天统万城地区的自然景观属于沙漠，仅存稀疏的次生灌丛和草本群落。但是，通过对统万城城墙内的孢粉和木材进行的综合研究表明，在约1600年前，当地为温带草原，在塬面或山丘上分布有侧柏林，沟谷、河岸边生长喜温湿的乔木，河流、湖泊、沼泽中水生植物繁盛，在丘间低洼处或盐碱土上分布有灌木和草本植物。当时该地区的年均温为7.8 ℃-9.3℃，最热月平均温度23.0℃-24.9℃，最冷月平均温度-12℃-5.6℃，年较差28.5℃-3 8.2℃，年降雨量403.4-550．Omm，最大月降雨量83.8-123.9mm，最少月降雨量4.4-12.2mm，当时气候比现在温暖湿润，年均温比现在高出0.2-0.7℃，年降雨量也高出60--lOOmm。而如此的历史景观今天已经向南迁移，侧柏林或森林草原退缩至延安以南地区。在此近1600年的时间里，毛乌素沙漠分布范围不断扩大，其南部边缘推进了约200 km，推测沙漠扩展的速率达到平均125m/a。

俄罗斯远东和中国湖南晚泥盆世石松类的新发现

在现代的陆地植被当中，石松类为草本植物，在植物界中属于高等植物的低等部分。然而在陆地植物起源和发展演化的早期阶段，石松类是陆地植被的重要成分。石炭纪时期石松类处于最繁盛时期，多生长成为高大乔木，形成森林，是陆地植被的优势类群，也是主要的成煤植物。作为演化历史最长的陆地植物之一，石松类在泥盆纪时期就广泛分布于世界各地，泥盆纪成为石松类演化发展的一个非常重要的时期。研究泥盆纪石松类对认识石松类的起源和发展有重要意义。 本论文是作者在博士期间多个工作之中的两个内容，对采自俄罗斯远东地区的晚泥盆世石松类Haskinsia标本以及采自湖南醴陵的晚泥盆世石松类Lilingostrobus longifolius标本进行了研究。 我们在俄罗斯远东地区的标本中发现了具有三角形叶片的简单叶。泥盆纪石松类Haskinsia属的最典型特征就是其叶由叶柄和三角形或戟形的叶片组成。综合标本的其它特征我们将这些标本归入Haskinsia colophylla这个种中。俄罗斯学者曾在与我们相同的采集地点采集了相似的标本并将其命名为Pseudolepidodendron igrischense，经过仔细对比后我们认为俄罗斯学者的标本也应归并入H. colophylla。同时根据Haskinsia属分布于早泥盆世晚期至晚泥盆世早期的特点，我们对采集地点的地层时代进行了修订，认为其地层时代要比俄罗斯学者认为的晚泥盆世至早石炭世要早。 我们在标本中还首次发现了Haskinsia colophylla这个种的孢子囊。在此之前，Haskinsia 属内的H. colophylla和H. sagittata由于具有相类似的叶而被认为可能是同一个种。由于仅在H. sagittata中发现了孢子囊（椭圆形/卵形）而没有发现H. colophylla的生殖结构，无法确切地区分这两个种。我们在标本中发现了着生于孢子叶腹面的圆形孢子囊。这一发现使我们确认了H. colophylla与H. sagittata的区别，这两个种都是有效种。 我们还对采自湖南醴陵望仙桥水库剖面晚泥盆统岳麓山组地层的部分石松类标本进行了研究。该石松类被命名为Lilingostrobus longifolius。它为木本石松类，茎为二岐分枝，叶在茎上螺旋形排列，叶为长披针形，具有中脉。孢子叶球顶生，呈长锥形，顶端钝圆，孢子叶在孢子叶球上呈紧密的螺旋形排列，每轮约6-8枚。孢子叶分化为孢子叶梗和孢子叶片。孢子叶梗与穗轴近垂直，水平向外延伸后向上弯曲成孢子叶片，叶片至少长45mm，超过孢子叶球长度的一半，孢子叶片与营养叶同型。孢子囊长椭圆形，着生于孢子叶梗的上面。Lilingostrobus longifolius为异型孢子叶球，分为大孢子叶球和小孢子叶球。茎轴具有外始式的初生木质部以及呈放射状的次生木质部。管胞次生壁具有梯纹加厚，加厚的横棒之间有纵向的条状物，即“威廉姆森结构”。Lilingostrobus longifolius具有孢子叶分化明显的孢子叶球因而被归入广义的水韭目。根据其管胞类型和孢子叶球特点，我们认为其可能与Sublepidodendron属亲缘关系较近。 通过对Lilingostrobus longifolius的孢子叶球以及解剖特点的分析，我们认为它代表了晚泥盆世石松类中较为先进的一个类群，这种类群在石炭纪时期得到大规模发展。 结合晚泥盆世其他具有生殖结构的石松类，我们认为晚泥盆世时期石松类的生殖结构类型丰富多样，而且远比中泥盆世石松类生殖结构复杂。这个时期石松类的发展为其在石炭纪的进一步演化奠定了基础。同时，在这个时期石松类植物的叶舌与孢子类型关系中，包括四种类型，即不具叶舌产生单型孢子类型，不具叶舌产生异型孢子类型，具叶舌产生单型孢子类型以及具叶舌产生异型孢子类型。这与现代石松类仅具有两种类型即不具叶舌的类群孢子囊产生同型孢子，而具叶舌的类群孢子囊产生异型孢子有很大的差别。