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Subzone. The third and most severe extinctionphase capped the Laframboise patch reef complex(Ellis Bay Formation), at the top of theNormalograptus persculptus Zone. In the paleotropics,the Hirnantian interglacials showedhigher biodiversity than either the precedingRawtheyan or following Rhuddanian (earlyLlandovery) warm intervals, a feature perhapsachieved by high innovation rates via introductionof "Silurian" reef biotas during theHirnantian. The Anticosti reef succession iscompared with latest Ordovician reefs fromnorthwestern Europe (Baltic Basin and U.K.),the northwestern margins of Gondwana (Spainand Austria), the Urals, Siberia, Kazakhstan,northeast Russia, and China. Reefs show aglobal decline from the late Caradoc through lateAshgill, marked by hiatuses towards the O–Sboundary. A protracted 3–4 million-year recoveryphase for Early Silurian tropical marine biotas,generally without reefs, marked the succeedingRhuddanian; full reef recovery was delayeduntil the mid-Aeronian.2008040032加 拿 大 魁 北 克 Charlevoix 地 区 一 个 南 方 永 冻泥 炭 田 的 古 生 态 分 析 = A paleoecologicalanalysis of a southern permafrost peatland, Charlevoix,Quebec. ( 英 文 ). Zimmermann C; LavoieC. Canadian Journal of Earth Sciences, 2001,38(6): 909-919The southernmost site where permafrost hasbeen located in the Quebec–Labrador peninsulais in a peatland on the subalpine summit of Lacdes Cygnes Mountain (47°41'N, 70°36'W). Becauseof the thickness of its peat deposit, this sitecontains rich ecological information about thehistory of the peatland and its surroundingsubalpine environment. We conducted a detailedmacrofossil analysis to reconstruct the 6000-yearhistory of the peatland. In general, the developmentof the Lac des Cygnes Mountain peatlandhas followed the classic succession of rich fen –poor fen – bog found in other peatlands in subarctic,boreal, and temperate environments. Anabrupt decline in all tree macrofossils ca. 4000BP suggests that a major deforestation eventoccurred on the summit of Lac des CygnesMountain. The exact cause of this deforestationevent is unknown, but fire is a possible factor.The lack of absolute chronological resolutionnear the top of the macrofossil record precludesproper dating of permafrost inception, but thebalance of evidence appears to indicate that thepermafrost is modern.2008040033阿 根 廷 西 北 部 高 纬 度 安 第 斯 湖 第 四 纪 湖 泊 石灰 华 和 叠 层 石 的 沉 积 环 境 = Depositional environmentsof Quaternary lacustrine travertinesand stromatolites from high-altitude Andeanlakes, northwestern Argentina. ( 英 文 ). Valero-Garcés B L; Arenas C; Delgado-Huertas A. CanadianJournal of Earth Sciences, 2001, 38(8):1263-1283Four distinctive depositional subenvironmentsof fossil travertines and stromatolites are identifiedin three high-altitude (3500–4000m abovesea level) lacustrine basins: El Peinado, SanFrancisco (Las Coladas Salar subbasin), and LasPeladas (southern Andean Altiplano, northwesternArgentina). These late Quaternary occurrencesare characterized using geomorphological,sedimentological, petrographic, and stable isotopicdata. Stromatolites of cyanobacterial originonly develop in shallow lacustrine margins of ElPeinado basin. In the same basin, macrophytictravertines occur both near thermal spring seepageareas along the lake margin as in situ faciesand in littoral lacustrine environments up to waterdepths of several metres as phytoclastic travertinefacies. The stromatolites and macrophytictravertines have relatively heavy 18 Ocompositions, suggesting initial16 O-depletedwaters and (or) evaporation effects through time.Their high 13 C compositions are interpreted as areflection of intense CO 2 evasion from the thermalgroundwaters feeding the lakes. Similarlaminated travertine facies, with no petrographicevidence for biotic origin, occur in both Las Coladasand Las Peladas basins. Neither petrographicnor isotopic data alone can differentiatebetween these two cases. Besides, diageneticoverprint in Las Peladas facies precludes the useof isotopic values as original isotopic signatures.However, the depositional environmental conditionsdefined by the geomorphological andsedimentological features are different. Laminatedaragonitic crusts in Las Coladas basinformed in a shallow, saline lake and are associatedwith shoreline and terrace deposits cementedby aragonite. These travertine crusts representperiods of spring, 16 O-rich discharge tothe lake, as suggested by the lighter oxygen isotopiccompositions. In contrast, travertines fromLas Peladas occur as laminated calcitic and aragoniticunits intercalated at the top of finingupwardsequences composed of conglomerates,sandstones, and intraclastic limestones. Sedimentologicaldata suggest that these travertinesoriginated in fluvial-influenced lake marginsduring low lake-level episodes.2008040034加 拿 大 北 部 和 东 部 奥 陶 纪 、 志 留 纪 及 泥 盆 纪腕 足 动 物 多 起 因 壳 质 钻 孔 的 统 计 分 析 = Statisticalanalysis of mixed-motive shell borings inOrdovician, Silurian, and Devonian brachiopodsfrom northern and eastern Canada. ( 英 文 ). Daley11