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Mattos, Nathália Helena Secol 1988. "Geoquímica e proveniência do Grupo Bauru no Oeste de Minas Gerais". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/286616.
Testo completoAbstract (sommario):
Orientador: Alessandro BatezelliDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências
Made available in DSpace on 2018-08-25T21:40:30Z (GMT). No. of bitstreams: 1 Mattos_NathaliaHelenaSecol_M.pdf: 5195246 bytes, checksum: 2551186b0e4a53abcac203b4227922a3 (MD5) Previous issue date: 2014
Resumo: Estudos geoquímicos e mineralógicos de arenitos e argilitos da Bacia Bauru (Cretáceo Superior), localizada na região do Triângulo Mineiro (Minas Gerais) foram realizados visando à determinação da proveniência, tectônica da rocha fonte, o papel de processos como intemperismo e reciclagem sedimentar na assinatura geoquímica da rocha fonte e à proposição de um modelo de evolução paleoambiental para a área de estudo. As amostras tem sua mineralogia principal composta por quartzo, microclínio, calcita, albita, dolomita e hematita. Illita, montmorillonita e paligorsquita são os argilominerais identificados. Elementos maiores, traços e terras raras e as razões elementares entre eles foram utilizadas para determinar a composição da rocha fonte. Valores do Índice Químico de Alteração e do Índice de Intemperismo Químico variando de 64 a 92 e de 84 a 98, respectivamente, e a ocorrência de feldspatos nas rochas sedimentares indicam intemperismo químico moderado na área fonte. Gráficos de elementos maiores e traços e valores para razões como La/Sc (1,47-4,86), (La/Yb)c (3,86-20,44) e a anomalia de Eu (Eu/Eu* = 0,62-0,92) comparados com dados da literatura sugerem que os sedimentos da Bacia Bauru na área de estudo tenham sido originados de rochas de composição quartzítica a granítico-gnáissica, derivadas de áreas continentais estáveis e depositados em ambientes de bacias intracratônica. A possível área-fonte para as rochas estudadas localiza-se a NE da Bacia Bauru, consistindo em rochas graníticas e metassedimentares do embasamento pré-cambriano. A deposição sedimentar na Bacia Bauru reflete a interação de processos aluviais e lacustres
Abstract: Geochemical and mineralogical studies of sandstones and mudstones from the Late Cretaceous Bauru Basin of Triângulo Mineiro region (Minas Gerais State) were undertaken to determine the provenance, tectonic setting, the role of weathering, sorting and recycling on the source rock geochemical signature and to propose a palaeoenvironmental evolution model to the study area. The analysed samples are mainly composed by quartz, microcline, calcite, albite, dolomite and hematite. Illite, montmorillonite and palygorskite are the identified clay minerals. Major elements were used to determine the source rock composition, as well as trace and rare earth elements and the ratios among them. Chemical Index of Alteration and Chemical Index of Weathering ranging from 64.83 to 92.3 and from 84 to 98.2, respectively, along with the feldspar occurrence on sedimentary rocks indicate a moderate weathering in the source area. Plots of major and trace elements and values for the ratios such as La/Sc (1.47-4.86), (La/Yb)c (3.86-20.44) and the Eu anomaly (Eu/Eu*= 0.62-0.92), compared to data from the literature indicate source rock was located into a continental passive margin tectonic setting and sediments were derived from quartzitic to granitic-gneissic rocks of stable continental areas and deposited in an intracratonic basin. Probable source area to the studied rocks is located at NE of Bauru Basin and consists in granitic and metassedimentary rocks from the Precambrian basement. Sedimentary deposition in Bauru Basin reflects an interaction of alluvial and processes
Mestrado
Geologia e Recursos Naturais
Mestra em Geociências
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Voltani, Cibele Gasparelo. "Redescrição osteológica comentada e aspectos paleoecológicos dos gêneros Notelops e Rhacolepis (Pachyrhizodontoidei) /". Rio Claro, 2016. http://hdl.handle.net/11449/141899.
Testo completoAbstract (sommario):
Orientador: Reinaldo José BertiniBanca: Roberto Goitein
Banca: Marise Sardenberg Salgado de Carvalho
Banca: Alcina Magnólia da Silva Franca
Banca: Maria Helena Ribeiro Hessel
Resumo: A Bacia do Araripe situa-se no Nordeste brasileiro, e sua área estende-se sobre os estados de Ceará, Pernambuco e Piauí. Esta bacia sedimentar apresenta formações geológicas de idade paleozoica e mesozoica em cujos estratos estão fossilizados diversos tipos de organismos. A Formação Santana, eocretácica, possui destaque em termos de diversidade e qualidade dos organismos fossilizados. O Membro Romualdo é o mais superior desta formação e representa o contexto no qual ocorrem os ictiólitos ou concreções calcárias portadoras de peixes fósseis, sendo fonte de cerca de 30 gêneros formalmente descritos. Destes gêneros, dois foram selecionados para redescrição osteológica, Notelops e Rhacolepis, mediante preparação mecânica e/ou química para a remoção de sedimento de modo a evidenciar estruturas ósseas. Além da osteologia dos gêneros mencionados, outros organismos associados também foram evidenciados, permitindo a observação de um passado "congelado" nas imediações da gênese dos ictiólitos viabilizando, assim, breves abordagens de aspectos paleoecológicos para os para os peixes fósseis redescritos nesta tese
Abstract: Araripe Basin is located in Brazilian northeast, and its area extends over Ceará, Pernambuco and Piauí states. This watershed presents geologic formations from the Paleozoic and Mesozoic ages in which strata are fossilized several kinds of organisms. The Santana Formation, Early Cretaceous, is highlighted in terms of diversity and quantity of fossilized organisms. Romualdo Member is the most superior of this formation and it is the context in which ichthyoliths or calcareous concretions bearing fossilized fish occurs, being the source of about 30 formally described genres. Of these genres, two have been selected for osteological redescriptions, Notelops and Rhacolepis, by mechanical and/or chemical preparation for sediment removal to evidence bone structures. Besides the osteology of these mentioned genres, other organisms in association with them were also evidenced, allowing the observation of a "frozen" past near the genesis of ichthyoliths, enabling thus brief observations of the paleoecological aspects for the fish redescribed in these Ph D Thesis
Doutor
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Silveira, Rosemery Rocha da. "Bioestratigrafia e paleoecologia de depósitos neógenos e pleistocenos aflorantes na porção central e ocidental da Bacia do Solimões, Estado do Amazonas, Brasil". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/132294.
Testo completoAbstract (sommario):
As 93 amostras palinológicas obtidas deste estudo são oriundas de 12 afloramentos relacionados às formações Solimões e Içá, na região de Coari (5 afloramentos) e Alto Solimões (7 afloramentos), Bacia do Solimões, no estado do Amazonas. Este trabalho apresenta os palinomorfos reconhecidos nestes depósitos (incluindo descrições quando necessárias), com registro fotomicrográfico, relativos a 11 taxons de esporos de fungos, 7 algas, 1 escolecodonte, 1 cisto de dinoflagelado, 31 esporos de pteridófitas, 2 grãos de pólen de gimnospermas e 48 grãos de pólens de angiospermas. Perfis compostos foram construídos para os depósitos aflorantes das regiões de Alto Solimões e Coari, com interpretação estratigráfica. A composição da palinoflora em ambas as áreas apresenta contrastes, sendo aquela de Alto Solimões a de menor diversidade, mas com maior abundância, em comparação com a de Coari. Na região do Alto Solimões há documentação de formas como Crassoretitriletes vanraadshooveni, Foveotriletes ornatos, Magnastriatites grandiosus e a ocorrência de um cisto de dinoflagelado, que confirma influência marinha local para a Formação Solimões. Na região de Coari foi verificado predomínio de esporomorfos, evidenciando contexto continental para as formações Solimões e Içá. Palinofósseis guias de zoneamentos palinológicos foram reconhecidos para a região do Alto Solimões, tais como Crassoretitriletes vanraadshooveni, Grimsdalea magnaclavata, Multimarginites vanderhammeni, Diphyes latiusculus, entre outros. A associação dessas formas permitiu posicionar os depósitos da Formação Solimões na região de Tabatinga e Atalaia do Norte entre o Serravaliano e o Tortoniano (Mioceno Médio/ Superior), com correspondência com a Zona Grimsdalea, pré-estabelecida para intervalo coevo da unidade. Para Coari as amostras foram posicionadas no Neomioceno/Plioceno, a partir do reconhecimento da Subzona de Intervalo de Fenestrites longispinisus, ainda que na área este apresente baixa frequência. Ainda na região de Coari são identificados depósitos mais jovens, a partir da presença de Alnipollenites verus, que indica idade Pleistocena.The 93 pollen samples obtained in this study were the result of research 12 outcrops related to Solimões and Içá formations in the region of Coari (5 outcrops) and Alto Solimões (7 outcrops) in the state of Amazonas. This paper presents the recognized palinomorphs (including descriptions when necessary) and photomicrographs of 11 fungal spores, 7 algae, 1 escolecodont, 1 dinoflagellate cyst, 31 fern spores and 48 pollen grains of angiosperms. The composition of palinoflora in both areas shows contrasts with that of the Alto Solimões less diverse, but more abundantly in comparison with the Coari. In the Alto Solimões is no documentation of ways Crassoretitriletes vanraadshooveni, Foveotriletes ornamentos, Magnastriatites grandiosus and the occurrence of a dinoflagellate cyst, confirming local marine influence to the Solimões Formation. In Coari region was verified predominance of esporomorphs, showing the continental context for the Solimões and Içá formations. Guides species of zonal schemes previously proposed were recognized for the Alto Solimões, such as Crassoretitriletes vanraadshooveni, Grimsdalea magnaclavata, Multimarginites vanderhammeni, Diphyes latiusculus, among others. The association of these forms allowed positioning of the deposits of the Solimões Formation in the region of Tabatinga and Atalaia do Norte on the edge of Serravaliano-Tortonian intervals (Miocene Middle and Upper), with correspondence with the Grimsdalea Zone, preset to coeval range of the unit. To Coari samples were placed in Neomioceno / Pliocene, from the recognition Interval Subdivision of Fenestrites longispinisus, although in this area has a low frequency. Still in the region Coari younger deposits are identified from the presence of Alnipollenites verus, which indicates age Pleistocene.
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Sudhaus, Dirk. "Paläoökologische Untersuchungen zur spätglazialen und holozänen Landschaftsgenese des Ostschwarzwaldes im Vergleich mit den Buntsandsteinvogesen /". Freiburg i. Br. : Institut für Physische Geographie der Albert-Ludwigs-Universität, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014181535&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Testo completo
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Glenwright, T. Lane. "Diatom-based palaeoecology of Kowloon Bay, Hong Kong /". Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22032423.
Testo completo
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Liu, Liping. "Chinese fossil Suoidea : systematics, evolution and paleoecology". Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/geolo/vk/liping/.
Testo completo
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Tosal, Alcobé Aixa. "Modelització paleoclimàtica del límit Eocè–Oligocè a Catalunya a partir de l’anàlisi CLAMP". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668462.
Testo completoAbstract (sommario):
Aquesta tesi té com a objectiu modelitzar el paleoclima del trànsit Eocè−Oligocè de la Conca de l’Ebre i conèixer com aquest canvi afectà a la flora local. Aquesta caracterització paleoclimàtica s’ha obtingut a partir de l’estudi de les fulles de dicotiledònies de les localitats de Sarral (Priabonià terminal) i Cervera (Rupelià inferior) mitjançant CLAMP (Climate Leaf Analysis Multivariate Program). Per altra banda, per tal de poder caracteritzar els canvis florístics entre ambdues localitats, s’ha estudiat la seva taxonomia, tafonomia i paleoecologia així com la sedimentologia dels dipòsits que inclouen les associacions fòssils.
S’han descrit setanta-cinc espècies de magnoliòpsides una de les quals, Rhus asymmetrica, és nova. La descripció s’ha basat en criteris moderns prenent en consideració caràcters com la nervadura terciària i detalls del marge foliar, fet que ha permès definir el polimorfisme intraespecífic d’algunes espècies. Tot i així en el futur caldrà revisar la taxonomia d’aquestes espècies comparant-les amb especies similars d’altres localitats europees contemporànies i amb les fulles d’espècies actuals afins.
Des del punt de vista paleoambiental les flores de les dues localitats estudiades s’estructuraven en biomes similars encara que de composició força diferent. Aquestes diferències han permès caracteritzar els canvis en la distribució de la vegetació, que van tenir lloc entre el Priabonià i el Rupelià a la Conca de l’Ebre. L’exemple més evident fa referència a la vegetació que ocupava la zona adjacent a la comunitat del bosc de ribera amb un accés indirecte de les seves restes als rius i al llac. En el Priabonià de Sarral aquest bioma estava dominat per Tetraclinis, formant una bosquina oberta de cupressàcies. En canvi, al Rupelià de Cervera les plantes que creixien darrera del bosc de ribera eren principalment Daphnogene, Laurophyllum, Myrica faya i M. oligocenica i formaven petites laurisilves.
Un altre bioma que mostra diferències notables entre les dues localitats estudiades fa referència a la part més allunyada dels llacs que estaria caracteritzada per una vegetació de tipus sabana. Aquest bioma mostrà una biodiversitat relativament baixa durant el Priabonià de Sarral, on estaria dominat per vuit espècies de fabals, Zizyphus zizyphoides i Pinus. Pel contrari, la comunitat equivalent en el Rupelià de Cervera estaria dominada per catorze espècies de fabals i set espècies d’altres grups taxonòmics tals com Rhamnus aizoon, Rhus asymmetrica i espècies afins com Toxicodendron.
L’anàlisi CLAMP de les flores estudiades a la Conca de l’Ebre mostra una tendència climàtica cap a un refredament i un augment de l’estacionalitat entre l’Eocè superior i l’Oligocè inferior, que concorda amb la tendència global observada a l’hemisferi nord. Tanmateix, també assenyala que la pluviometria era més elevada a l’Oligocè de Cervera que al Priabonià de Sarral, fet que seria l’oposat de la tendència generalment acceptada vers un augment de l’aridesa al sud d’Europa durant aquest període. Aquests resultats reflectirien un canvi climàtic més complex del què s’havia documenatat fins ara. L’anàlisi de fàcies aporta dades clau per interpretar els resultats de la modelització mitjançant CLAMP. En aquest sentit, la flora de Sarral es trobaria en els períodes secs d’una seqüència de somització lacustre interpretada com a moments de màxima precessió. Per altra banda, la flora rupeliana de Cervera reflectiria els estadis humits dels cicles sedimentaris de somització lacustre, que correspondrien als cicles orbitals de precessió mínima. Aquestes condicions climàtiques específiques de cada localitat permeten comprendre els canvis en la composició i la distribució de la vegetació detectats per l’estudi paleoecològic. Per exemple, la temperatura elevada i la pluviometria baixa del Priabonià de Sarral haurien afavorit les plantes adaptades a bosquines obertes i de tipus sabana dominades per les fabals o Tetraclinis. Alhora, aquelles espècies amb un requeriment hídric més elevat, com les lauràcies, s’haurien vist obligades a créixer en zones relativament més humides, concretament al bosc de ribera. En canvi, les condicions ambientals amb una temperatura més moderada i una pluviometria més alta en el Rupelià de Cervera haurien permès el desenvolupament de moltes altres famílies de plantes al costat de les fabals, especialment les anacardiàcies. L’increment de la pluviometria a l’Oligocè de Cervera hauria beneficiat que els llorers s’expandissin fora del bosc de ribera formant petites comunitats de laurisilva.
La combinació dels estudis sedimentològics, tafonòmics, paleoecològics i paleoclimàtics ha permès comprendre les interaccions entre el clima i la vegetació durant el trànsit Eocè−Oligocè a la Conca de l’Ebre. La sobreimposició de cicles climàtics d’ordre menor (cicles orbitals de precessió) en els cicles d’ordre major (cicles d’excentricitat) produiria un canvi climàtic no lineal. Els paràmetres pluviomètrics fluctuants van condicionar enormement l’evolució de les comunitats vegetals i probablement es trobarien en l’origen d’una vegetació resistent a aquestes variacions, com és la flora Mediterrània.
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Briles, Christy Elaine. "Holocene vegetation and fire history of the floristically diverse Klamath Mountains, northern California, USA /". Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/7486.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2008.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 217-227). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
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Sandau, Stephen D. "The Paleoclimate and Paleoecology of a Uintan (Late Middle Eocene) flora and fauna from the Uinta Basin, Utah /". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd719.pdf.
Testo completo
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Minckley, Thomas A. "Holocene environmental history of the northwestern Great Basin and the analysis of modern pollen analogues in western North America /". view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3113019.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2003.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 294-310). Also available for download via the World Wide Web; free to University of Oregon users.
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Klug, Christopher Allen. "Lower Permian through Lower Trassic [sic] paleontology, stratigraphy, and chemostratigraphy of the Bilk Creek Mountains of Humboldt County, Nevada". Bowling Green, Ohio : Bowling Green State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1184878826.
Testo completo
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Carter, Brian D. "Paleoecological reconstructions of the South African Plio-Pleistocene based on low-magnification dental microwear of fossil primates". unrestricted, 2006. http://etd.gsu.edu/theses/available/etd-11302006-174657/.
Testo completoAbstract (sommario):
Thesis (M.A.)--Georgia State University, 2006.Title from title screen. Frank L. Williams, committee chair; Cassandra White, Susan C. McCombie, committee members. Description based on contents viewed June 25, 2007. Includes bibliographical references (p. 89-99).
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Samuels, Joshua Xavier. "Paleoecology and functional morphology of beavers (family castoridae)". Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1495959451&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Testo completo
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Tarrats, Sada Pol. "Chrinomids as lake paleoenvironmental indicators: the role of present fauna to understand the past". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/462104.
Testo completoAbstract (sommario):
The study of past ecological changes is highly useful for understanding how ecosystems have responded to climate and human-induced disturbances. It is thus relevant in the context of climate change, as it allows several ecological processes and properties, such as ecosystem baseline conditions or resilience, to be evaluated. This thesis focuses on the study of past ecological changes in mountain lakes, which are widely considered to be sentinel ecosystems due to their ability to effectively record signals of climate change and anthropogenic impacts in their sediments.
To do this we use Chironomidae (Diptera) as model organisms. The use of chironomids as lake paleoenvironmental indicators has a long tradition, mainly in terms of quantitative temperature reconstructions. However, there are still many uncertainties involving their reliable use as paleoindicators that need to be further tested. Moreover, their use in paleoecological studies in the Iberian Peninsula is still scarce. In this context, this thesis focuses on two main issues. On the one hand, it reveals the main drivers affecting the chironomid paleorecord by comparing living and recent subfossil assemblages. On the other hand, past changes (mainly temperature and hydrological changes) are reconstructed in two morphologically different lakes from the Iberian Peninsula.
This thesis demonstrates the key influence of macrophyte habitat in shaping the chironomid community, both in the living larvae community and acting as a major confounding factor in the subfossil chironomid record. The presence of Chara in Enol Lake is identified as one of the main drivers affecting the living community. These effects are amplified in the recent subfossil record due to the high chironomid productivity related to this habitat. These results warn against the use of recent subfossil data without further questioning, as they can be greatly affected by a single factor, biasing qualitative or quantitative environmental reconstructions. Moreover, they indicate the importance of studying the present-day fauna before conducting paleoenvironmental studies.
Our results also show that, in many cases (e.g. deep lakes), it might be necessary to analyse more than one core (which is usually retrieved at maximum lake depth) to perform complete and reliable paleoenvironmental reconstructions. The comparison of two sediment cores retrieved from different lake zones (sublittoral and profundal) shows several differences in terms of how chironomids recorded past changes. The deeper core records some hydrological fluctuations, but is also characterized by low head capsule densities, which could lead to less reliable interpretations of downcore changes. The shallower core records the main anthropogenic impacts, in addition to some hydrological oscillations. In this case, results are more robust due to the high chironomid densities found in this core.
Finally, this thesis provides the first chironomid-based temperature reconstruction covering the entire Holocene in the Iberian Peninsula. The comparison of these results with other local and regional studies highlights similarities and differences between this new reconstruction and previous records. These differences can be attributed to different patterns of temperature, hydrology and seasonality changes throughout the Holocene in our study region.
Taken as a whole, this thesis constitutes one of the first complete studies regarding chironomid remains in the Iberian Peninsula and opens up many new research opportunities, in this region and elsewhere. According to the main findings of this study, the combination of ecological and paleoecological approaches is advised for carrying out complete paleoenvironmental studies.L’estudi dels canvis ecològics esdevinguts en el passat és de gran utilitat per entendre com han respost els ecosistemes davant de pertorbacions de tipus climàtic i humà. Per aquest motiu és rellevant en el context del canvi climàtic, ja que permet avaluar diverses propietats i processos ecològics, com ara les condicions basals o la resiliència dels ecosistemes. Aquesta tesi se centra en l’estudi de l’evolució dels canvis ecològics en llacs de muntanya que, per l’eficàcia en la seva capacitat d’enregistrar senyals de canvis climàtics i impactes antròpics en els seus sediments, són àmpliament acceptats com a ecosistemes sentinella. Per fer-ho, s’utilitzen els quironòmids (Diptera) com a organismes model. L’ús dels quironòmids com a indicadors paleoambientals lacustres té una llarga tradició, principalment pel que fa a reconstruccions quantitatives de temperatura. Tanmateix, encara hi ha diverses incerteses respecte a la seva fiabilitat com a paleoindicadors que aconsellen un estudi més profund. A més, el seu ús en estudis paleoecològics a la Península Ibèrica encara és escàs. En aquest context, aquesta tesi se centra en dos aspectes principals. D’una banda, revela els principals factors que modelen el registre subfòssil mitjançant la comparació entre les comunitats actuals i les subfòssils recents. D’una altra banda, es reconstrueixen els canvis esdevinguts en el passat (principalment hidrològics i de temperatura) en dos llacs de diferents característiques de la Península Ibèrica. Aquesta tesi demostra la influència clau de l’hàbitat de macròfits en el modelatge de la comunitat de quironòmids, tant en la comunitat actual de larves com actuant com a principal factor de confusió en el registre subfòssil. La presència de Chara al Llac Enol s’identifica com un dels principals elements que afecta la comunitat actual. Aquests efectes s’amplifiquen en el registre subfòssil recent a causa de la gran productivitat de quironòmids relacionada amb aquest hàbitat. Aquests resultats indiquen que no es poden utilitzar dades subfòssils recents sense qüestionar-les prèviament, ja que es poden veure afectades en gran mesura per un únic factor, fet que podria generar un biaix en les reconstruccions ambientals qualitatives i/o quantitatives. A més, indiquen que és molt important estudiar la fauna actual abans de dur a terme estudis paleoambientals. Els resultats obtinguts també mostren que, en molts casos (p. e. llacs profunds), caldria analitzar més d’un testimoni de sediment, que normalment s’obté a la zona més profunda del llac, per a dur a terme reconstruccions paleoambientals completes i fiables. La comparació de dos testimonis de sediment recuperats en diferents zones d’un llac (sublitoral i profunda) mostra nombroses diferències en la manera en què els quironòmids van enregistrar els canvis esdevinguts en el passat. El testimoni profund registra algunes fluctuacions hidrològiques, però també es caracteritza per unes densitats de càpsules cefàliques més baixes, fet que podria comportar una interpretació menys fiable dels canvis. El testimoni més somer registra els principals impactes antròpics, a més de diverses oscil·lacions hidrològiques. En aquest cas, els resultats són més sòlids gràcies a les elevades densitats de quironòmids trobades en aquest testimoni. Finalment, aquesta tesi aporta la primera reconstrucció de temperatura a la Península Ibèrica a partir de quironòmids que abarca tot l’Holocè. La comparació d’aquests resultats amb d’altres estudis locals i regionals permet destacar similituds i diferències entre aquesta nova reconstrucció i altres registres previs. Aquestes diferències es poden atribuir a diferents patrons de canvis de temperatura, hidrologia i estacionalitat al llarg de l’Holocè en la regió objecte del nostre estudi. En general, aquesta tesi constitueix un dels primers estudis complets sobre restes de quironòmids a la Península Ibèrica i obre diverses noves oportunitats de recerca, tant en aquesta regió com en d’altres. D’acord amb els principals resultats obtinguts en aquest estudi seria, doncs, recomanable combinar aproximacions ecològiques i paleoecològiques per dur a terme estudis paleoambientals complets
15
Cook, Lewis A. "Systematics and evolutionary paleoecology of crinoids from the St. Louis Limestone (Mississippian, Meramecian) of the Illinois Basin". Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11042.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains x, 180 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references (p. 149-172).
16
Sessa, Jocelyn A. "The dynamics of rapid, asynchronous biotic turnover in the middle Devonian Appalachian basin of New York : a thesis /". Connect to The dynamics of rapid, asynchronous biotic turnover in the middle Devonian Appalachian basin of New York (Online), 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=1054576413.
Testo completo
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Cheung, Man-ching, e 張敏青. "Holocene paleo-environmental reconstruction in central Tibetan plateau inferred from a lacustrine sediment record". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/211563.
Testo completoAbstract (sommario):
Previous studies on reconstructing the paleoclimate on the Tibetan Plateauare commonly based on a single proxy, and have thus limited the usage of their results. Therefore this study was designed firstly to evaluate the applicability of organic carbon isotopes from modern plants in the Tibetan Plateau as a paleo-environmental proxy, and secondly to apply palynology, organic geochemistry and biomarkers to the reconstructions ofpaleo-environmental history of central Tibet. The new, comprehensive records reveal the history of regional precipitation, temperature and vegetation change in responding to Holocene climatic changesin the region.
Organic carbon isotope (δ13C) and lipid n-alkanes were measured from plant samples collected from various altitudes and environments across the study area. The δ13C results indicate the importance of availability of water to C3/C4 herbs distribution in this alpine region. The molecular distributions of trees, shrubs, herbs and submergent macrophytes show distinctive features in a number of indices. These indices are considered to be useful for paleo-environmental reconstructions.
A 5.8m-long peat core, which were dated back to 95,000 yr BP was obtained from a river valley at an altitude of 4300 m above sea level. The pollen data from the core reveals a sparse herbaceous vegetation in the catchment area during early Holocene, suggesting non-favourable conditions for vegetation growth. The environment became wetter during the early mid-Holocene around 8100-7000 cal. yr BP, and since then a sedge-dominated wetland habitat was developed. This vegetation changed little until about 1100 cal. yr BP; from which an increase of drought-tolerant herbs was indicated by the pollen data, implying a slightly drier condition of the latter part of late Holocene. The pollen record suggests that the optimum precipitation in central Tibet occurred later and lasted longer than that in the East Asian Monsoon region.
Finally, bulk sample carbon geochemistry(TOC, δ13C) as well as the biomarkers analysis on n-alkanes and GDGTs as paleo-limnology and paleo-temperature indicators respectively were applied to the core. Before 1500 cal. yr BP, the wetland was dominated by both vascular herbs as suggested by the δ13Cdata and aquatic floating/submerged macrophytes as indicated by mid-chain n-alkanes. The relative proportion of the two sources of organic matter input varied slightly, and vascular herbs increased in two episodes(5400 -4700 and 2800 -2300 cal. yr BP) indicated by the increase of long-chain n-alkanes (>n-C25). Considering of the soil water content variation by the ratios of iGDGTs to bGDGTs, the change between the two plant communities could to be caused by different lake status. GDGTs paleo-temperature reconstruction indicates a warm period from 6700 to 6000 cal. yr BP, which is believed to be the warmest and highly humid in central Tibetan region. Then the temperature decreased towards the late Holocene, consistent with other paleo climate records across the Plateau region, i.e. largely controlled by change of solar insolation. Along the decreasing trend, a warm episode at about 1200 yr BP that inferred from MAAT was suggested corresponding with the North Hemisphere Medieval Warming.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
18
Sawada, Michael Charles. "Late quaternary paleoclimates and biogeography of North America". Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9031.
Testo completoAbstract (sommario):
Pollen, spores, and dinoflagellate cysts are used with the modern analog technique (MAT) to provide paleoclimate reconstructions for terrestrial and marine environments in northeastern North America. Multivariate analysis of marine and nearby terrestrial pollen sequences from Hudson Bay, Labrador and the St. Lawrence, differentiate tundra, boreal and deciduous forest assemblages in time and space. These three regions had differing climate histories with respect to deglaciation and air mass boundaries. Prior to 6000 14C yr BP, cooler temperatures reconstructed along the Labrador margins agree with climate simulations indicating a persistent anticyclone over the Quebec-Labrador ice sheet. A late Holocene cooling at forest-tundra sites suggests a recent southern movement in the mean position of the polar front. The degree to which those critical thresholds of dissimilarity, that are used to identify non-analog pollen assemblages, are due to limitations of the modern pollen database or critical decisions within the MAT are explored by means of stochastic simulation, spatial statistics and graphical techniques. Critical thresholds of SQD, as derived by the expected value under randomization, become greater as the number of taxa in the pollen set increases. Larger pollen sets, with continentally infrequent but regionally abundant taxa, better distinguish between continental vegetation zones. Global and local spatial autocorrelation within climate anomalies indicate where the modern sample network induces biases in the climate reconstruction using the MAT. The spatial scale of terrestrial climate or vegetation reconstructions from pollen in lake-sediments is investigated through the study of pollen source area in southern Quebec. Despite the different regional vegetation, estimated pollen source areas and relevant pollen productivity for Pinus, Picea, Abies, Fagus, Quercus and Tsuga are consistent with studies from Michigan, Wisconsin and Sweden. These estimates are robust with respect to various plant abundance distance-weighting schemes and imply that the same inferences can be made regarding plant abundance from pollen throughout a lake-derived fossil pollen sequence. Stochastic simulations illustrate that the definition of relevant pollen source area requires consistent within-site vegetation heterogeneity within a network of pollen sites. Underutilized proxy-climate data from wetland taxa are demonstrated to contain climate signals at the continental scale and have the potential to further our climatic and biogeographic picture of North America over the past 21,000 years. Pollen and spores from modern wetland taxa conform to their geographic ranges and allow interpretations of their past range changes. The climatic tolerances that govern their geographic distributions are used to interpret past range changes in climatic terns. Sphagnum spore distributions suggest major peatland developments after 9 ka and 5 ka. Sphagnum, Potamogeton, Isoetes, Myriophyllum Typha/Sparganium, and Menyanthes trifoliata were in Alaska during the last glacial maximum (LGM) and moved into the ice-free corridor by 13 ka. Since the LGM, four migration routes for aquatic taxa are identified in response to the climate changes of the late Quaternary.
19
Deschamps, Eric Martin. "Mammalian paleoecology of a Caverne de la Mine (Quebec, Canada): Analysis of an early Holocene cave deposit". Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9197.
Testo completoAbstract (sommario):
The aim of this study is to analyse a mammalian terrestrial fossil fauna in order to assess the early Holocene fauna of the St. Lawrence-Ottawa valley region. The fossils were excavated from Caverne de la Mine located on the Eardley Escarpment in Gatineau Park, western Quebec, near the city of Ottawa (45°28'18"N, 75°51'01"W). The fossil deposit dated between 5 020 +/- 70 and 8 230 +/- 80 B.P. yielded twenty-three taxa among ten mammalian families. Two species, Dicrostonyx hudsonius and Microtus pinetorum, are not part of the modern local fauna. Analysis of the fossil assemblage has shown that most species constituting the local fauna were established in the region soon after deglaciation. However, shifting community structure and the presence of extirpated taxa suggest that the local fauna underwent some adjustments since the beginning of the Holocene. The faunal adjustments mirror evolving vegetation cover in the area. (Abstract shortened by UMI.)
20
Bouchard, Giselle. "Freshwater diatom biogeography of the Canadian Arctic Archipelago". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26589.
Testo completoAbstract (sommario):
The biogeography of diatoms in 62 lakes across the Canadian Arctic Archipelago was studied. A total of 326 taxa was found, with up to 85 and as low as 8 taxa identified in any one lake. Rarefaction-estimated richness correlated with lake size. Although diatom assemblages showed regional patterns, between-lake variability in any region was high, indicating that local factors are important in determining the assemblages. Newly delineated genera showed interpretable geographic patterns and could be related to environmental factors, suggesting that this more natural grouping may enhance our understanding of diatom ecology. Some taxa showed southern and regionally limited distributions. Many taxa prefer colder temperatures while others were more influenced by lake water parameters. Assemblages with zero or low abundance of fragilaroid taxa tended to occur in larger lakes with higher silica. These lakes had more diverse assemblages including Gomphonema, Encyonema , and Encyonopsis taxa, suggesting a possible relationship between non-fragilaroid taxa and lake size and silica. Geographic, physical, and chemical factors are needed to explain diatom distributions in the Arctic.
21
Lacourse, Terri. "Late Quaternary vegetation history of Sulphur Lake, southwest Yukon Territory, Canada". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0005/MQ36711.pdf.
Testo completo
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Brooks, A. M. "The systematics, paleoecology and stratigraphy of British Palaeozoic scolecondonts". Thesis, Open University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375541.
Testo completo
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Sakakura, Norihiko. "Taxonomy and paleoecology of Paleogene Cyclocardia (Bivalvia) from Japan". 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149544.
Testo completo
24
Falzoni, F. "SANTONIAN-CAMPANIAN PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY, TAXONOMY AND ISOTOPE PALEOECOLOGY". Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/169982.
Testo completoAbstract (sommario):
Current biozonations based on Santonian-Campanian (Late Cretaceous) planktonic foraminiferal bioevents do not provide a high stratigraphic resolution, when compared to other time intervals. Moreover, some of the marker species of the Tethyan biozonation show a diachronous lowest occurrence across latitudes and a restricted geographic distribution. Thus, paleoclimatic and paleoceanographic inferences are poorly constrained by biostratigraphy and, in addition, are often based on diagenetically altered material.
This study is aimed to 1) improve the biostratigraphic resolution of Santonian-Campanian zonal schemes based on planktonic foraminiferal bioevents; 2) reconstruct the evolutionary history of key biostratigraphic species and revise the taxonomy of problematic groups (planispiral and globigeriniform taxa) often overlooked in the literature; 3) infer the paleoecological preferences of selected planktonic foraminiferal species based on stable isotope analyses, and 4) reconstruct the paleoclimatic context of the Santonian-Campanian time interval.
The Santonian-Campanian samples analyzed in this study were selected from four different localities: 1) Tanzania - western Indian Ocean (Tanzanian Drilling Project - TDP Sites 23, 28, 32 and 35); 2) Shatsky Rise - northwestern Pacific Ocean (Ocean Drilling Program - ODP Leg 198, Hole 1210B); 3) Exmouth Plateau - eastern Indian Ocean (ODP Leg 122, Hole 762C); 4) Bottaccione section outcropping in the Umbro-Marchigian Apennines near Gubbio (Italy). Samples were prepared following the standard methodologies and considering the different lithologies. A scanning electron microscope (SEM) was used to document the species, observe and describe the wall texture of the specimens at higher magnification. Cathodoluminescence analyses on selected specimens were applied to assess the degree of wall alteration. Well-preserved specimens were finally analyzed to obtain reliable δ18O and δ13C values and provide paleotemperature estimations.
Results allow description of the mid Campanian Contusotruncana plummerae Zone, defined as the stratigraphic interval between the appearance of the nominate species and of Radotruncana calcarata and suggest that Globotruncanita atlantica is a promising marker species useful to correlate early Campanian stratigraphic sections especially at low latitudes. In addition, several bioevents (i.e., the lowest occurrence of Contusotruncana morozovae, Rugoglobigerina hexacamerata, Radotruncana subspinosa and the extinction of Hendersonites carinatus) also appear reliable for detailed correlations across latitudes.
Stable isotope results suggest that Santonian Marginotruncanids behave as spring/autumn dwellers in the surface water column. During the Campanian, C. plummerae, Contusotruncana fornicata and Globotruncana bulloides inhabited the summer mixed layer, whereas Globotruncanita stuartiformis and Globotruncanita elevata proliferate in the cool winter sea surface. Globotruncana orientalis, Globotruncana mariei, Globotruncana arca and Gublerina rajagopalani were more adapted to stable and deeper environments close to the permanent thermocline. Interestingly, data show that Heterohelix sphenoides and C. plummerae were likely adapted to particularly 13C-enriched environments. High δ13C values have been interpreted as the isotopic signal indicating a symbiotic relationship between these species and photoautotrophic algae. However, results show that this kind of relationship is not supported by clear evidences and should be investigated by further and more detailed isotopic analyses.
Paleoclimatic reconstructions inferred from Tanzanian pristinely preserved planktonic foraminifera suggest that Santonian-Campanian subtropical sea-surface temperatures reached 30°C, hence, 4° to 5°C warmer than modern mean values. Oxygen isotopic values measured on planktonic foraminifera from Shatsky Rise and Exmouth Plateau indicate up to 10°C cooler and 20°C warmer temperatures, respectively, when compared to modern mean values. These results would support the “cool tropic paradox” hypothesis, that Late Cretaceous equatorial and tropical sea surface temperatures were several degrees lower than modern mean values. This hypothesis implies a different climatic scenario with respect to the traditional interpretation of the greenhouse world that would predict an Earth global warming. However, the observed secondary recrystallization of planktonic foraminiferal shells from Shatsky Rise and Exmouth Plateau led to an overprinting of the original isotopic signal and thus to erroneous paleotemperature estimations, whose extent is, however, still unknown.
Taxonomic analyses of well preserved and diversified planktonic foraminiferal assemblages allowed description of one new species (Globotruncana neotricarinata) and identification of three new morphotypes (Globigerinelloides n. sp. 1, Muricohedbergella n. sp. 1 and Costellagerina n. sp. 1) that are surely new species. The formal description of these taxa is in progress. Stratophenetic observations and isotopic analyses on Rugoglobigerina species indicate that the development of the meridional ornamentation represents an adaptation to different ecological parameters of the water masses. This study suggests that more reliable diagnostic criteria, other than the development of the ornamentation, should be applied to discriminate among Costellagerina, Rugoglobigerina, and Archaeoglobigerina.
25
Glenwright, Thomas Lane. "Diatom-based palaeoecology of Kowloon Bay, Hong Kong". Thesis, Click to view the E-thesis via HKUTO, 2000. http://sunzi.lib.hku.hk/hkuto/record/B42575576.
Testo completo
26
White, Stephanie. "Effects of drilling predation on global turritellid diversity and abundance a potential catalyst for evolution /". View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-3/whites/stephaniewhite.pdf.
Testo completo
27
Junior, Antonio Alvaro Buso. "Dinâmica dos Espodossolos, da vegetação e do clima durante o Quaternário tardio na região nordeste do estado do Espírito Santo". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-24082015-142743/.
Testo completoAbstract (sommario):
Esse trabalho, realizado na região nordeste do estado do Espírito Santo, é dividido em duas partes. A primeira envolve a caracterização da precipitação polínica moderna da vegetação de mata de tabuleiros e de duas fisionomias de vegetação de muçununga. A segunda consiste na reconstrução paleoambiental no Quaternário tardio, com base em estudo interdisciplinar aplicado a Espodossolos e sedimento lacustre. A caracterização da precipitação polínica moderna mostrou que a mata de tabuleiros é marcada por maiores taxas de acumulação polínica, maiores frequências de Urticaceae/Moraceae e presença de táxons raros, tais como Glycydendron, Rinorea, Hydrogaster, Virola e outros. A vegetação da muçununga arborizada foi caracterizada por taxa de acumulação polínica intermediária, altas frequências de Byrsonima, e frequências mais elevadas de Araliaceae, Doliocarpus e Lundia. A vegetação de muçununga campestre é caracterizada por menores taxas de acumulação polínica e maiores frequências de Poaceae, Cyperaceae e Asteraceae. A comparação desses resultados com amostra superficial de sedimento lacustre mostrou que em amostras sedimentares o sinal polínico de mata de tabuleiros pode ser mascarado pela alta frequência de espécies semi-aquáticas das famílias Poaceae e Cyperaceae, e por altas frequências de espécies pioneiras, tais como Cecropia. O estudo de reconstrução do paleoambiente permitiu a elaboração de um modelo para a evolução das manchas de Espodossolo da região, as quais sustentam as diferentes fisionomias da vegetação de muçununga. Segundo esse modelo, essas manchas seriam originárias da transformação do Argissolo devido a fatores relacionados ao relevo e a paleoclimas mais úmidos. Entretanto, não é possível descartar a possibilidade de que algumas manchas de Espodossolo tenham se originado em sedimentos intrinsecamente arenosos relacionados ao Pós-Barreiras. O estudo também permitiu inferir flutuações do paleoclima durante o Quaternário tardio. Um clima mais úmido no intervalo aproximado de 31000-23000 anos cal. AP, com chuvas bem distribuídas ao longo do ano, é inferido com base no início do processo de podsolização e no desenvolvimento de algumas das atuais manchas de Espodossolo. O intervalo seguinte, aproximadamente entre 23000-8000 anos cal. AP, é inferido como menos úmido que o anterior, com base na expansão pontual de plantas C4 observada na matéria-orgânica do solo, e na ausência do sinal polínico de mata de tabuleiros entre 11000-8000 anos cal. AP no sedimento lacustre. O último intervalo, entre cerca de 7000 anos cal. AP até hoje, é inferido como mais úmido, com base no início do registro polínico em área de Espodossolo alagado e formação de horizonte B espódico secundário, e também na expansão das matas de tabuleiros observada no sinal polínico do sedimento lacustre. O registro polínico sedimentar mostra a presença de táxons com distribuição disjunta entre os biomas Amazônia e Mata Atlântica desde cerca de 8500 anos cal. AP. O registro polínico, a matéria-orgânica sedimentar e a matéria-orgânica dos solos não mostram indícios de expansão de campos e savanas com predomínio de plantas C4 durante os últimos 17000 anos cal. AP, o que pode indicar que a região pode ter sido um refúgio florestal durante os períodos menos úmidos do Pleistoceno tardio e do HolocenoThis study was carried out at the northeastern region of the Espírito Santo State, Brazil. It is organized in two main parts. The first one is related to the characterization of the modern pollen rain of the \"tabuleiros\" forest vegetation and of two distinct physiognomies of mussununga vegetation. The second part consists of the late Quaternary paleoenvironment reconstruction, based on interdisciplinary study applied in Spodosols and lake sediment. The modern pollen rain of the \"tabuleiros\" forest is characterized by the highest pollen accumulation rates, highest frequencies of Urticaceae/Moraceae, and the presence of less frequent and rare taxa as Glycydendron, Rinorea, Hydrogaster, Virola, and others. The wooded mussununga vegetation is characterized by intermediate pollen accumulation rates, high frequencies of Byrsonima, and high frequencies of Araliaceae, Doliocarpus and Lundia when compared with the other vegetation types. The grassland mussununga vegetation is characterized by the lowest pollen accumulation rates, and the highest frequencies of Poaceae, Cyperaceae and Asteraceae. The comparison of these results with the pollen assemblage from lake sediment surface sample shows that in sediment samples the \"tabuleiros\" forest signal may be masked by high frequencies of semi aquatic herbs, mainly Poaceae and Cyperaceae, and pioneer species, especially Cecropia. The paleoenvironment reconstruction study allowed the development of a model for the evolution of Spodosol spots in the region, which sustain the distinct physiognomies of the mussununga vegetation. According to this model, these Spodosol spots originate from the transformation of the Ultisol due to factors related to the relief and more humid paleoclimate events. However, some of these Spodosol spots may have evolved on intrinsically sandy Post-Barreiras sediments. The paleoenvironment study also allowed some inferences about late Quaternary climate fluctuations. Based on the beginning of the podsolization process and on the evolution of some Spodosol spots, the climate during the interval from ~31,000-23,000 cal yr BP may have been humid, without dry period along the year. The next interval, from ~23,000 to 8000 cal yr BP is inferred less humid than the previous one, based on the spatially restricted expansion of C4 plants, observed in the soil organic matter, and on the absence of the \"tabuleiros\" forest pollen signal, from ~11,000 to 8000 cal yr BP, in the lake sediment. The climate of the last interval, from ~7000 yr cal BP to the present, is inferred more humid than the previous one, based on the beginning of the pollen record in a flooded Spodosol site, and on the expansion of the \"tabuleiros\" forest in the pollen record of the lake sediment. Geographically disjunct taxa between Amazonia and Atlantic Forest biomes are present in the pollen record from the lake sediment since ~8500 cal yr BP to the present. Pollen records, and sediment and soil organic matter do not show the expansion of grasslands or savannas dominated by C4 plants during the last 17,000 cal yr BP, which may indicate that the region probably was a forest refuge during the less humid intervals of late Pleistocene and Holocene
28
BADINO, FEDERICA. "Holocene vegetation and climate variability as recorded in high-altitude mires (western Italian Alps)". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2016. http://hdl.handle.net/10281/131067.
Testo completoAbstract (sommario):
Climate variability during the Holocene (the last 11700 calendar yr b2k) is relatively subtle whether compared with the higher amplitude characterizing the last glacial period. Nonetheless, several proxy data (e.g. pollen, plant macrofossils, glacier length variations), indicate detectable changes in temperature and/or moisture during this period. Retreating glaciers may uncover peat sequences that were once ice-buried. Palynological analysis of those organic deposits provides information on plant communities colonization in proglacial areas as well as long-distance vegetations signal.
The aim of this study is to investigate the potential of high-altitude pollen records for vegetation history and climate reconstruction during the Holocene in the south-western Italian Alps. The study sites are located in the Rutor Glacier area (La Thuile Valley). Within this thesis, modern (a) and past (b) vegetation and climate conditions have been analyzed using different methodologies;
a) Modern pollen rain, vegetation, climate and terrain parameters have been collected at 27 sampling sites placed along an altitudinal gradient from the village of Morgex (983 m asl) to the Rutor Glacier forefield (2668 m asl). This altitudinal training set has been designed (i) to provide a robust modern reference for reliable palaeoenvironmental and quantitative interpretations of past changes in vegetation composition; (ii) to integrate the newly-obtained pollen spectra into a large, continental dataset of modern pollen samples (EMPD - European Modern Pollen Database) for quantitative climate reconstructions.
b) New paleoecological, stratigraphical and geochronological data have been obtained from peat deposits (Lac dans la Roche peat bog, 2594 m asl) and integrated with the well-known buried peat sequences exposed at 2510 m asl by the '80es Rutor Glacier retreat. The result is a composite paleoecological record covering most of the Holocene.
At the base of the composite sequence, meltwater glacier sediments testify to the early Holocene development of a proglacial lake, before Abies alba expansion in the western Italian Alps. These sediments bear the palynological evidence of a primary plant succession testifying to an ecological mechanism of colonization on deglaciated terrains. Moreover, macrofossil analysis highlighted the local presence of alpine dwarf - shrubland species (e.g. Salix cfr. foetida).
Pinus cembra occurs rather densely in the alpine belt from ca. 8000 yrs cal. BP, representing the beginning of the Holocene thermal maximum in the high Alps.
Between 8000 - 4000 yrs cal. BP timberline was higher than today. A radiocarbon age obtained from a Pinus cembra wood fragment suggests the occurrence of pines as high as ca. 2600 m asl at around 5650 yrs cal BP. The dated wood fragment cannot have been long-distance transported, thus it indicates the presence of this species in situ. Moreover, paleobotanical insights and comparison with climate threshold of modern treeline (ca. 9,3° C at 2400 m asl), suggest a positive treeline shift of almost 150 m. Preliminary pollen-inferred Tjul reconstructions show higher values (up to 2 - 3°C) than today for this interval.
At around 4000 yrs cal. BP Picea abies and Alnus viridis started to expand. A progressive natural/climatic driven decline of Pinus cembra took place. Pollen inferred Tjul shows a decreasing trend between 2900 – 2000 yrs cal BP and possibly a short-lived cold event starting at ca. 1140 yrs cal. BP, pre-dating the onset of the LIA (Little Ice Age). A subsequent arolla pine forests reduction can be attributed to LIA glacier advance (max occurred between 1751 – 1864 AD), which is testified in the upper part of the sequence by fluvioglacial deposits.
29
Bonde, Joshua William. "Paleoecology and taphonomy of the Willow Tank Formation (Albian), Southern Nevada". Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/bonde/BondeJ1208.pdf.
Testo completoAbstract (sommario):
This study documents fossil remains from the Willow Tank Formation and places those remains into a taphonomic and sedimentological context in order to determine the paleoecology of southern Nevada during the Early Cretaceous (Albian). Recovered taxa include Lepisosteidae, Ceratodus, Holostean A, Naomichelys, Baenidae, c.f. Adocus, possible Trionychidae, Crocodyliformes, Thyreophora, Iguanodontia, Titanosauriformes, Tyrannosauroidea, Dromaeosauridae, indet. Theropoda, and two fern morphotypes. Sedimentology of the fossiliferous unit of the Willow Tank Formation suggests these taxa were deposited in an anastomosed fluvial system. Interpretation of an anastomosed fluvial system is based in part upon an overwhelming abundance of overbank fines, single storied channel fills, lack of lateral accretion structures, and common crevasse splay sandstones. Observed paleosols commonly contain carbonate nodules associated with mottled red-green mudrocks. The carbonate nodules are consistent with as seasonally arid environment and reddening of beds may suggest a well drained floodplain. Taphonomic modes include microsite, subaqueous bonebed, subaerial bonebed, and channel fill assemblages. Vertebrate fossils are found predominantly in overbank settings. The fauna of the Willow Tank Formation most resembles that of the Cedar Mountain Formation. Unlike the discrete, temporal, fauna assemblages of the various members of the Cedar Mountain Formation, the Willow Tank Formation fauna contains a mix of these different stratigraphic faunas. One example is the co-occurrence of Early Cretaceous iguanodon-grade and Late Cretaceous hadrosaur-grade teeth. Another example being the presence of a tyrannosauroid tooth in Albian beds of the Willow Tank Formation, where tyrannosauroids are not found in the Cedar Mountain Formation until the Cenomanian. Therefore, Willow Tank Formation strata may shed light on biogeographic and evolutionary relationships at the Early-Late Cretaceous boundary.
30
Bergolc, Melanie L. "A Paleoenvironmental Analysis Using Fossil Insects in Late Quaternary Deposits in Indiana and Ohio". Bowling Green State University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1092940677.
Testo completo
31
Bahman, Heedar. "REEVALUATING THE MIOCENE MOLLUSK SYSTEMATICS, LITTLE COVE POINT MEMBER, ST. MARYS FORMATION, AND EXAMINING THEIR PALEOECOLOGY, PALEOBIODIVERSITY". Kent State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=kent1625579235981025.
Testo completo
32
Hu, Feng Sheng. "An ecosystem approach to the study of late-Quaternary environmental change in southwestern Alaska /". Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/5577.
Testo completo
33
Calede, Jonathan J. 1988. "Systematics and paleoecology of northern Great Basin Mylagaulidae (Mammalia: Rodentia)". Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11435.
Testo completoAbstract (sommario):
xx, 281 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Burrowing rodents are important ecosystem engineers in today's environments. The fossil record offers the opportunity to study patterns and processes in the evolution of the burrowing rodent guild through the Cenozoic. During the Miocene, this guild was very diverse, including numerous families ranging in ecology from semi-fossorial to subterranean. I use the emblematic family Mylagaulidae, a group of subterranean rodents, to test hypotheses of abiotic and biotic controls on mammalian evolution with the goal of better understanding turnover in the composition of the fossorial rodent guild in the Miocene of the Great Basin. I investigate the relative contributions of climate and biotic interactions to the purported intraguild competition between mylagaulids and geomyids with an emphasis on differences and similarities in patterns of occurrence and diet. Patterns of site occupancy and microwear suggest the importance of habitat changes in driving changes in guild composition among burrowers.
Committee in charge: Dr. Samantha S.B. Hopkins, Chair; Dr. Madonna Moss; Dr. Gregory J. Retallack
34
Simpson, Emily. "Paleoecology and Land-Use of Quaternary Megafauna from Saltville, Virginia". Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3590.
Testo completoAbstract (sommario):
Land-use, feeding habits, and response to seasonality by Quaternary megaherbivores in Saltville, Virginia, is poorly understood. Stable isotope analyses of serially sampled Bootherium and Equus enamel from Saltville were used to explore seasonally calibrated (δ18O) patterns in megaherbivore diet (δ13C) and land-use (87Sr/86Sr). Overall, this dataset suggests an open forest with relatively constant temperatures year round that were similar to modern conditions. Neither Bootherium or Equus individuals spent a significant amount of time at higher elevations in the nearby Blue Ridge geologic province. These analyses provide a unique perspective on long-term response of large mammals to climatic shifts and their impact on local ecosystems. Results are also relevant to modern conservation decisions, especially those surrounding highland grassy balds in the Appalachians, and their maintenance by grazing pressure.
35
Connely, Melissa V. "Stratigraphy and Paleoecology of the Morrison Formation, Como Bluff, Wyoming". DigitalCommons@USU, 2002. https://digitalcommons.usu.edu/etd/6736.
Testo completoAbstract (sommario):
The Morrison Formation at Como Bluff, Wyoming, has been historically known for containing a rich source of Late Jurassic vertebrate fossils. However, when collected, most of these fossils were not positioned into a stratigraphic or sedimentologic framework. Research shows that the Morrison Formation at Como Bluff can be divided into three members. These members can be identified by lithologic and paleontological characteristics. The lower Morrison members include the Windy Hill Member and the recently described Lake Como Member. The Windy Hill Member primarily contains near-shore marine sandstone. Megavertebrate fauna is lacking. The Lake Como Member contains illitic clay in red and green mottled paleosols with caliche and thin sandstone beds. The fauna typically consists oflarge saurian and ornithischian dinosaurs. The upper Morrison Formation includes the Talking Rocks Member. This member contains gray-green smectite-rich mudstones. The Talking Rocks Member is generally calcareous and appears to have a megavertebrate fauna similar to the Lower Morrison. The upper part of this member is typically non calcareous and the fauna is more aquatic with turtles, crocodiles, fish and smaller ornithischian dinosaurs, including some species thought to be restricted to the Cretaceous Period. The contact between the Morrison Formation and the overlying Cloverly Formation is placed at the base of the Cloverly conglomerates, which are present throughout the region. In some areas, this boundary coincides with the Jurassic/Cretaceous boundary. However, in sections of the study area, a zone of kaolinitic carbonaceous shale with Cretaceous-like plant material can be found just below the Morrison/Cl overly contact. If this bed is Cretaceous in age, then the Morrison Formation at Como Bluff is in part Early Cretaceous and not restricted to the Late Jurassic.
36
Suteethorn, Suravech. "Sauropod dinosaurs of the Southeast Asia : systematic, evolution and paleoecology". Montpellier 2, 2009. http://www.theses.fr/2009MON20088.
Testo completo
37
Whitmore, Johanne. "North American and Greenland modern pollen data for multi-scale paleoecological and paleoclimatic applications". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26807.
Testo completoAbstract (sommario):
The status of the modern pollen network in North America and Greenland is presented by assembling a database for use in quantitative calibration studies and paleoenvironmental reconstructions. The geo-referenced database includes 4569 samples from all regions of the continent. The database includes 934 pollen taxa that range from common taxa to those that may be used for regional-scale reconstructions. Climate data and vegetation characteristics are assigned to every site. A series of procedures, both automated and manual, were used to check the qualify of the pollen data. Data are currently available for almost all of North America, with variable density. The squared-chord distance computed between samples shows that most modern pollen samples find analogues in the same vegetation zone and the temperature and precipitation computed from the best analogue are highly correlated with actual value at the site. Analysis of the contemporary distribution of pollen taxa in relation to their vegetation range illustrates factors that must be considered when using these data as well as the potential for more detailed analysis of understudied taxa.
38
Shiraki, Masahiro. "Upper Devonian sponge-algal mud mounds, southern flank of Miette reef complex, Jasper National Park, Alberta, Canada". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27409.
Testo completoAbstract (sommario):
A series of small mud mounds are exposed in the McConnell and Miette thrust sheets on the southern flank of the Miette reef complex. They occur on the southeastward inclined carbonate clinoforms of the late Frasnian Arcs Member. These mounds are rooted on marine, argillaceous lime mudstones and are surrounded by lime mudstones of several prograding clinoforms of the upper Arcs Member or dolomitic siltstones of the lower Ronde Member.Mounds are approximately 17 to 36 m high and 32 to 81 m wide and columnar to domal in shape. The lower part of the mounds consists of sponge-rich wackestones and packstones, and locally laminar stromatoporoid boundstones. Calcareous green algae tend to predominate in the upper parts of the mounds.
Variable cavities occur and are filled with geopetal sediments, isopachous fibrous and blocky calcite cements. The most common cavity types, irregular and irregular stromatactoidal cavities, might be related to organic origins, possibly the decay of sponges in conjunction with submarine cementation.
Abrupt mound margins indicate that the mounds grew upwards more rapidly than the accumulation of the adjacent basin and clinoforming slope sediments. (Abstract shortened by UMI.)
39
Rashid, Harunur. "The deep-sea record of rapid late pleistocene paleoclimate change and ice-sheet dynamics in Labrador sea sediments /". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38540.
Testo completoAbstract (sommario):
Thirty eight piston cores and numerous seismic profiles collected by two R/V Marion Dufresne and several CSS Hudson cruises were examined and cores from other cruises reinterpreted in the course of this study of Late Pleistocene ice-rafting events (Heinrich events) in the Labrador Sea.In the northwestern Labrador Sea, close to the margin of the former Laurentide Ice Sheet, Heinrich layers are unusually thick. Thicknesses of up to 4.8 m result from deposition from nepheloid-flows and low-density turbidity flows and from iceberg melting. Heinrich layers formed in three stages, explained by a proposed model that also attempts to explain ice-sheet dynamics, ice-stream behavior, and sediment transfer mechanisms from the ice-sheet to the deep sea. Nepheloid-flow deposits seem to result largely from fresh water buoyantly rising out of giant turbidity currents generated at the Hudson Strait outlet.
High-resolution stratigraphic records of oxygen isotopes, concentration of total carbonate, coarse-fraction content, and magnetic susceptibility, and 70 new 14C-AMS dates establish the presence of eight Heinrich events, H0 to H6 in the northwest Labrador Sea, including a new event, termed H5a (between H5 and H6). This refined chronology shows that the recurrence intervals between Heinrich events are fairly evenly spaced, with an average of ∼7 ka, as postulated by the binge and purge model for their origin.
High-resolution oxygen isotope, concentration of total carbonate, and coarse-fraction content data suggest that both meltwater and iceberg supply increased during Heinrich events. This is the first time that increased meltwater supply by direct discharge from a major ice outlet during Heinrich events has been documented, because ice-proximal areas tend to be barren of foraminifera.
The presence of H3 between 46° and ~63°N in the Labrador Sea, previously debated, has been proved. Thickness variations for H3 were compiled on an isopach map showing a maximum thickness of 4.8 m near Hudson Strait and thinning to 30 cm in the central Labrador Sea.
H0 is present in upper Labrador slope cores, compared to other Heinrich layers which were found widely on the slope, rise, and in the basin. These findings suggest that during or prior to H0, the Hudson Strait ice-stream had retreated landward, so that glaciomarine sediments were delivered to the shelf and iceberg trajectories were following the course of the already established Labrador Current.
40
Herring, Erin Mauryeen. "Late Quaternary and Holocene paleoecology of interior mesic forests of northern Idaho". Thesis, University of Oregon, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3644438.
Testo completoAbstract (sommario):
The mesic forests distributed within the Rocky Mountains of northern Idaho are unique because many species contained within the forest are separated from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within the inland disjunction survived the glacial periods of the Pleistocene, or whether they were more recently dispersed from coastal populations. To see if the dominant tree taxa of the mesic forests today could have persisted in a refugium south of the large ice sheets, four sediment cores were used to reconstruct the vegetation and climate history of the region. A nearly continuous record of pollen and sediment composition (biogenic silica and inorganic and organic matter) over the last ca. 120,000 years provides evidence of a dynamic ecosystem. Over a long timescale, the slow shifts in vegetation are attributed to the changes in climate. During the last interglacial period, the region was warmer and drier with a Pinus dominated mixed conifer forest. Approximately 71,000 years ago, a Pseudotsuga/Larix forest became established in the area as a response to the increased available moisture. As climate cooled and glaciers expanded the Pinus and Picea forest was the dominant vegetation type until ca. 40,000 years ago. The environment during the Last Glacial Maximum (LGM) was so harsh that no vegetation record was recorded. After the LGM, climate warmed, enabling a Pinus and Picea forest to establish and persist until the Holocene.
The mesic taxa that dominate the modern forests did not arrive in northern Idaho until the mid- to late-Holocene. The recent arrival of the dominant tree species, Thuja plicata and Tsuga mertensiana, suggests that they likely did not persist in a refugium during the last glaciation. Instead, these species recently dispersed from coastal populations, but expansion into their interior distributions was likely limited by both climate and species competition in already established forests. During the late-Quaternary, the deposition of thick tephra layers (>20 cm) from the eruptions of Glacier Peak (ca. 13,400 years ago) and Mt. Mazama (ca. 7,600 years ago) also facilitated an abrupt and persistent change in vegetation in northern Idaho.
41
Rode, Sandra Lee 1955. "FORAMINIFERA AS A TEST OF HERITABILITY OF SPECIATION POTENTIAL". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276479.
Testo completoAbstract (sommario):
If species selection shapes the history of clades, we should be able to detect its impact within well-established monophyletic descent groups. We should find that high rates of speciation/extinction are heritable. Demonstrating that high speciation/extinction rates have not been transmitted along known lines of descent would prove that species selection had not played an important role with the descent group under study. I have screened speciation rates within the Cenozoic planktonic foraminifera for heritability. Neither modified parent-offspring tests nor rank concordance tests reveal inheritance of this trait.
42
Leone, Karen L. "Sedentism in the Middle Woodland: Archaeobotanical Evidence from the Strait Site". The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392307246.
Testo completo
43
Anton, Ann. "Paleolimnology of an equatorial lake in the Inter-Andean Plateau of Ecuador /". The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487326511714434.
Testo completo
44
Kempf, Hannah Lowe. "Comparisons of Ecosystem Dynamics Before and After Invasion Reveal Consequences of Invasive Species in Benthic Marine Communities". Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1524830000208304.
Testo completo
45
Mitchell, Emily Geraldine Harmsworth. "Quantitative approaches to understanding ediacaran ecology". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664750.
Testo completo
46
Cole, Simon L. "Paleoenvironmental reconstruction of the Upper Mississippian Reynolds Limestone in the central Appalachian Basin of West Virginia". Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3971.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains viii, 136 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 75-79).
47
Biondi, Franco. "Spatial and temporal reconstruction of twentieth-century growth trends in a naturally-seeded pine forest". Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186783.
Testo completoAbstract (sommario):
This research uncovered growth trends from 1920 to 1990 in a stand of south-western ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. scopulorum), and investigated the role of climate and competition in shaping the observed trends. I focused on a 800 x 400-m permanent plot maintained by the U.S. Forest Service since 1920 near Flagstaff, Arizona. Temporal growth trends were quantified by size class using a mixed linear model applied to forest inventories, repeated at 10-year intervals. Tree density and stand basal area increased from 1920 to 1990, but growth rates of individual trees declined regardless of size class. Growth of large pines, whose density increased slightly, declined more than that of small pines, whose density almost tripled. I argued that competition for resources reduced growth rates of large trees more than those of small trees. Geostatistical analyses showed that, from 1920 to 1990, stem size was spatially autocorrelated over distances no greater than 30 m, a measure of average patch diameter. Tree density increased by increasing the number of pine groups rather than their horizontal dimension. Increased tree crowding corresponded to lower average, variance, and spatial dependence of individual growth rates. Since growth variation was less related to inter-tree distance at higher tree densities, density-dependent limitation of tree growth did not necessarily correspond to distance-dependent growth rates. No significant trend from 1910 to 1990 was found in climatic variables computed from daily meteorological records. Dendroclimatic analyses showed that climate-tree growth relations had not significantly changed over the twentieth century. Annual growth of both large and small pines was positively related to winter snowfall and to July monsoon rainfall. Periodic basal area increment obtained from dendrochronological data revealed that forest inventories over-estimated growth rates, especially for small pines. On the other hand, tree-ring chronologies developed using different standardization options showed different temporal trends. Repeated forest inventories quantified growth of individual trees and of the entire stand, but integrated bark and wood increment. Dendrochronological data had superior temporal resolution and accuracy, but their limited spatial coverage hindered representation of growth trends for the entire stand.
48
Tanck, Glen S. 1951. "Distribution and origin of organic carbon in the Upper Cretaceous Niobrara Formation and Sharon Springs Member of the Pierre Shale, Western Interior, United States". Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282423.
Testo completoAbstract (sommario):
The Upper Cretaceous Niobrara Formation and the overlying Sharon Springs Member of the Pierre Shale are two of several organic-carbon (OC) rich units deposited in the Western interior seaway. A key to assessing the validity of models proposed to account for OC enrichment in these units is understanding the three-dimensional (3D) distribution of OC within these units. Within the study area abundant subsurface data in the form of geophysical well logs are available. These logs were used to divide the Niobrara and Sharon Springs into regionally correlatable chronostratigraphic horizons and to estimate OC-content. By combining these elements a 3D picture of the OC-distribution was obtained. This distribution was compared to changes in lithology, sedimentation rate, and tectonic activity. The Niobrara and Sharon Springs contain local and regional disconformities which indicate water depths were near an estimated storm-wave base depth of 100 m. Local disconformities in the Niobrara are indicative of basinal tectonic activity that is linked to Sevier thrusting to the west. Large-scale Niobrara chalk/marl cycles also appear to be linked to Sevier thrusting. There is a regular vertical pattern of OC enrichment in the Niobrara, but no pronounced regional patterns are evident. Estimated paleoproductivities are moderate, except to the southeast where higher productivities may have been a consequence of upwelling. Small-scale chalk/marl cycles result from alternation of high productivity during periods of fairly vigorous circulation (chalks) with low productivity during periods of more sluggish circulation (marls). The regional diachrony of the Sharon Springs facies was a result of clastic dilution associated with progradation from the west and the paleobathymetry. Paleoproductivities were moderately high during Sharon Springs deposition, but there is no conclusive evidence of upwelling. Both units were deposited beneath bottom waters that were on average dysoxic, but oxygenation levels varied intermittently from fully oxic to anoxic. These changes were climatically modulated. At short time scales they may have been seasonal and at longer time scales they may have been driven by Milankovitch cyclicity.
49
Pierazzo, Elisabetta 1963. "The Chicxulub impact event and the environmental catastrophe at the end of the Cretaceous Period". Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282564.
Testo completoAbstract (sommario):
Impact events may have affected the evolution of life on Earth. The mass extinction event at the end of the Cretaceous Period, which includes the demise of the dinosaurs, has been linked to the large impact event that produced the Chicxulub structure located in the Yucatán Peninsula, Mexico. Unfortunately, the geologic record is too spotty to prove any causal relation between the impact event and the mass extinction event that occurred 65 Myr ago. However, the size and location of the impact structure have drawn attention to impact-related abrupt perturbations of the climate and their effects on the biota. My main approach to studying these impact-related perturbations is through hydrocode models of the impact event. Few simulations of the Chicxulub impact event have previously been done. In these simulations the event was modeled as an asteroid impact, using two-dimensional hydrocodes that permit modeling only vertical impacts (i.e. perpendicular to the surface). This work presents the results of a series of high-resolution two- and three-dimension hydrocode simulations of the Chicxulub impact event. The simulations span several different projectile sizes, cover asteroid as well as comet impacts, and explore the effects of impact angle on the impact event. The focus of the simulations is to obtain reliable estimates of the climatically active gases, namely S-bearing gases, CO₂ and water vapor, released to the atmosphere by the impact event. These estimates will be used in modeling the perturbation of the climate of the end of the Cretaceous, and, hopefully, will shed new light on the relation between the impact event and the mass extinction that occurred 65 Myr ago.
50
Van, de Water Peter Kent. "δ¹³C and stomatal density variability in modern and fossil leaves of key plants in the western United States". Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/289058.
Testo completoAbstract (sommario):
During the last deglaciation, 15,000 to 12,000 calendar years ago, global warming and wholesale shifts in regional precipitation patterns produced dramatic changes in vegetation worldwide. Paleobotanical records, namely pollen and macrofossils, have been used not only to reconstruct shifts in plant distributions and abundances, but also to quantify changes in temperature and precipitation amounts or seasonality. In addition to climatic change, during the full glacial period atmospheric CO₂ values had dropped 30% to 200 ppmv compared to the Holocene, preindustrial value of 280 ppmv. Hypothetically, variations in atmospheric CO₂ affect plant water-use efficiency (carbon gained to plant-water transpired) and thus may have modulated vegetation response as climates change. The studies incorporated in this dissertation focused upon carbon isotope and morphological changes in leaves of key functional groups. The studies concentrated on plant species that are abundant in the fossil record and comprise major floral components of past and present vegetation. Key findings include: (1) that shifts in δ¹³C in modern populations along steep environmental gradients seldom exceeds inter-plant variability at a given site, (2) inter-plant and intra-site variability in modern and historic herbarium collections of the C₄ halophytes Altriplex canescens and A. confertilfolia and packrat midden macrofossils of A. canescens excludes their use as a reliable proxy for atmospheric δ¹³C, (3) calcium-oxalate crystals are common component in plant tissue and can have a significantly different δ¹³C value that increases inter-plant variability, especially in C₄ plants such as Atriplex canescens and A. confertifolia, (4) carbon isotope and stomatal density/index measurements of macrofossils from packrat middens show species specific adaptation in ecophysiological processes as atmospheric CO₂ rose from the full glacial, and (5) the greatest adaptation to low atmospheric CO₂ during the last ice age was in the C₃ species and that C₄ and CAM plants showed few changes in their discrimination against ¹³C or in the number of stomata on their leaf surfaces.