The Holocene Paleoecology of Jenny Lake Area, Southwest Yukon, and Its Implications for Prehistory

The pollen stratigraphy of a core extracted from Jenny Lake, southwest Yukon, in 1984 has marked archaeological significance. Five palynological zones are identified as follows: Zone JL1, the oldest (ca. 12,500-9,500 B.P.), is a Betula shrub tundra assemblage; Zone JL2 (ca. 9,500-8,500 B.P.) an Alnus shrub tundra; Zone JL3 (ca. 8,500-4,500 B.P.) a Picea forest; Zone JL4 (ca. 4,500-2,000 B.P.) a Picea-Alnus woodland; and JL5 (ca. 2,000 B.P.-present) a Picea forest. The widely held belief that the Kluane-Aishihik area of the SW Yukon was covered by extensive grasslands well into the Holocene period is not supported by the palynology of the Jenny Lake Core. Instead, palynological evidence suggests that the area, which initially was a Betula shrub tundra, then Alnus shrub tundra, became a Picea-dominated forest by approximately 8,500 B.P. and remained forested to the present. The hypothesis stating early prehistoric hunters and gatherers in the SW Yukon were adapted to extensive Holocene grasslands until ca. 3,300-2,600 B.P. will have to be modified in view of these findings.Key words: Yukon, paleoecology, palynology, archaeologyMots clés: Yukon, paléoécologie, palynologie, archéologi

A lower bound on branching programs reading some bits twice

AbstractBy (1, + k(n))-branching programs (b.p.'s) we mean those b.p.'s which during each of their computations are allowed to test at most k(n) input bits repeatedly. For a Boolean function computable within polynomial time a trade-off is presented between the size and the number of repeatedly tested input bits of any b.p. P computing the function. Namely, if at most k(n) repeated tests are allowed, where log2 n ⩽ k(n) ⩽ n(1000 log2 n), then the size of P is at least exp(Ω(n(k(n)log2 n))12). This is exponential whenever k(n) ⩽ nα for a fixed α < 1 and superpolynomial whenever k(n) = o(nlog32 n).The presented result is a step towards a superpolynomial lower bound for 2-b.p.'s which is an open problem since 1984 when the first superpolynomial lower bounds for 1-b.p.'s were proven (Wegener, 1988; Žák, 1984). The present result is an improvement on (Žák, 1995)

Estudio polínico de la turbera del Cueto de la Avellanosa, Polaciones (Cantabria)

[Resumen] El presente trabajo trata del estudio poIínico de una turbera en el Cueto de la Avellanosa, Polaciones (Cantabria). Incluye un diagrama polinico con las especies arbóreas y no arbóreas correspondiente a los 3,4 metros del perfil de la turbera; lo que supone el tratamiento de 34 nuestras de turba que han sido estudiadas desde el punto de vista micropaleontol6gico o paleopolínico. También fueron datadas 3 muestras mediante el 14C. y la edad obtenida xwestra que la turba se formó entre los 6.020 años B.P. y los 1.100 años B.P. El inicio de la turbera se produce durante la transición entre el Boreal y el Atlántico, y tanto estos dos periodos como el Subboreal y Subatlántico aparecen bien definidos en el Palinograma. El conjunto del espectro polinico muestra que la turba se generó bajo condiciones más frias que otros depósitos de turba estudiados en la región Cantábrica o zona Norte.[Abstract] This paper describes the palinological study carried out in a peat deposit in Polaciones (Cantabria, Spain). A 3,4 m profile was obtained and 34 samples were studied. 14C. ages were also determined. The data obtained shows that the peat was formed between 6.020 years B.P. and 1.100 years B.P. starting during the transition between the Boreal and Atlantic, the Subboreal and Subatlantic periods appear well defined in the diagrams. On the whole, the polinic assemblege shows the the peat was formed under colder conditions than other peat deposits studied in the Cantabrian regio

Late Quaternary Vegetation History of Sulphur Lake, Southwest Yukon Territory, Canada

Paleoecological studies based on the analysis of pollen in lake sediments offer the potential for high resolution and well-dated independent records of past vegetation and climate. A 5 m sediment core was raised from the deepest section of Sulphur Lake, located in the southwest Yukon (60.95°N, 137.95°W; 847 m a.s.l.). The pollen spectra indicate that before 11250 yr BP, the vegetation was a herbaceous tundra marked by the presence of Artemisia. However, the date of the establishment of this initial vegetation cannot be secured because of problems with the basal radiocarbon date and the lack of a reliable chronology of regional deglaciation. A birch shrub tundra prevailed between 11250 and 10250 yr BP and was then replaced by a discontinuous poplar woodland. Juniperus populations expanded at 9500 yr BP, and by 8400 yr BP, Picea invaded the region. The white spruce forest that occupies the region today was established by approximately 8000 yr BP. Alnus crispa increased at 6000 yr BP, but the simultaneous increase in Picea mariana found at most sites in the Yukon was not present at Sulphur Lake. Black spruce was never a dominant component of the vegetation in the southwest Yukon, as it was in the south-central Yukon between 6100 and 4100 yr BP.Les études paléoécologiques fondées sur l'analyse de pollens de sédiments lacustres offrent la possibilité d'obtenir une chronologie de la paléovégétation et du paléoclimat à haute résolution et avec une datation précise. Une carotte de sédiment de 5 m a été prélevée dans la section la plus profonde de Sulphur Lake, situé au sud-ouest du Yukon (60,95° N., 137,95° O.; 847 m alt.). D'après les spectres polliniques, la végétation a été une toundra herbacée marquée par la présence d'Artemisia avant 11 250 ans B.P. Cependant, la date de colonisation de cette végétation ne peut être déterminée de façon définitive à cause des problèmes de datation du début de la séquence sédimentologique et l'absence d'une chronologie fiable de la déglaciation régionale. Une toundra arbustive à bouleau a prédominé entre 11250 B.P. et 10250 ans B.P., et a ensuite été remplacée par une région boisée de peuplier discontinu. Les populations de Juniperus ont augmenté vers 9500 ans B.P. et, vers 8400 ans B.P., Picea a colonisé la région. La forêt relativement fermée d'épinettes blanches qui occupe la région aujourd'hui s'est établie vers 8000 ans B.P. Alnus crispa s'est répandu il y a environ 6000 ans B.P. Alors qu'on retrouve une augmentation de Picea mariana à cette époque dans la plupart des sites dans le Territoire du Yukon, celle-ci n'a pas eu lieu à Sulphur Lake. L'épinette noire n'a jamais été une composante dominante de la végétation au sud-ouest du Yukon comme elle l'a été entre 6100 et 4100 ans B.P. au centre-sud du Yukon

Estudo Malacológico de Sambaquis de Momuna (Iguape - SP) e o seu significado paleoambiental

The shell-middens present in the Iguape (São Paulo State) coastal plain are situated at different distances from the present shoreline. In general, the more external shell-middens, which show a dominance of Anomalocardia brasiliana shells, give younger ages than the more internal shell-middens, which correspond to the Holocene most important lagoon expansion occurred between 5 and 6 ky B.P., and are commonly composed of Crassostrea brasiliana shells. Moreover, it was observed that the &#948;13C(PDB) ratios of the shells change according to the geographic location of the shell-middens, as a function of RSL (Relative Sea-Level) fluctuations with time. In this paper, the malacofauna of the shell-middens of the Momuna 1 and 2, both located at the homonymous village (Iguape, São Paulo State, Brazil), on the Cananeia Formation (120 ky B.P.), was studied.Na planície costeira de Iguape (SP) ocorrem sambaquis, que se acham situados a diferentes distâncias da atual linha de costa. Em geral, os sambaquis mais externos apresentam idades mais novas com predominância de conchas de Anomalocardia brasiliana, enquanto que os sambaquis mais internos, correspondentes à fase de maior expansão lagunar holocênica, entre 5 a 6 ka B.P., comumente apresentam a Crassostrea brasiliana. Além disso, têm sido verificado que as razões &#948;13C(PDB) das conchas variam segundo as posições geográficas dos sambaquis, em função das flutuações do NRM (nível relativo do mar) com o tempo. Neste trabalho foram estudadas malacofaunas de sambaquis de Momuna 1 e 2, situados na localidade homônima (Iguape, SP), sobre terraços pleistocênicos da Formação Cananeia (120 ka B.P.)

Deglaciation of the Reisa Valley, Northern Norway, and Studies of Glacial Deposits and Dispersal Processes

Durante el retroceso glacial en el area del Valle de Reisa, los principales valles estuvieron ocupados por glaciares marginales que descendían hacia los fiordos. Se han podido detectar cuatro momentos separados de avance o estancamiento de los hielos, marcados por las morrenas marginales correspondientes a acumulaciones del frente glacial. Las morrenas más antiguas, morrenas de Reisatjord, son correlacionables con las morrenas de Ra del Dryas reciente. Las morrenas más jóvenes son de edad Preboreal, 9900-9800 B.P., 9700-9500 B.P. y 9400 $ 250 B.P. respectivamente. Posteriormente el retroceso glacial se caracterizó por los efectos de una gran actividad fluvioglacial. A lo largo del límite entre Finlandia y Noruega, al W del Valle de Reisa, el drenaje del agua de fusión estuvo dirigido por el hielo hacia el Este, más o menos transversalmente a la dirección Norte del movimiento del hielo. Una serie de canales de desagüe cmzaban las divisorias. Los estudios realizados sobre sedimentos de estos depósitos proglaciales muestran una génesis y procedencia complejos. Las composiciones litológica y geoquímica son distintas, generalmente, de la:; de los tills. La composición del till presenta también variaciones verticales. La parte más profunda del till, en contacto con la roca, generalmente es de procedencia local. En las regiones interiores en la parte alta del till predomina el material transportado distancias superiores a los 5 Km. en la parte central de la cuenca de drenaje de Reisa el recubrimiento de till es más delgado y los depósitos glaciales tienen un origen más local. El till sólo contiene un 50% del contenido original en granito rojo después de 5-6 km. de transporte

An Evaluation Of Short-Term Prognostic Significance Of Various Clinical Parameters In Patients Of Stroke

Sonali Saxena', Shadab A. Khan", Jalaj Saxena’" * Consultant Cardiologist, ** Professor (Medicine), *** Assistant Professor (Physiology) Ishwardevi Medical and Cardiology Centre, Kanpur J.N. Medical College, A.M.U., Aligarh and G.S.V.M. Medical College, Kanpur ABSTRACT: Objectives :To predict the short-term prognostic significance of various clinical parameters at the time of admission in patients of stroke. Setting: Department of General Medicine, J.N. Medical College, A.M.U., Aligarh Participants : 100 patients of stroke (Cerebro-vascular accident) comprising 54 males and 46 females. Clinical Parameters : Admission Blood Pressure, Side of paralysis, Extent of Paralysis, Gastro-intestinal Haemorrhage, Level of consciousness at the time of admission. Statistical Analysis: ‘Z’ test (Z&gt;_ 1.96). Results : The admission B.P. was raised in 75% of patients. The mortality was significantly high (57.1%) in the severe grade B.P. while recovery was significantly high (64.3%) in mild or moderate grade B.P patients. The left sided paralysis was having significantly high mortality of patients (49%) while recovery was significantly high (56.2%) in the patients with right sided paralysis. The paralysis with Grade O power was in 58% of stroke patients and was associated with signifi­cantly high (53.4%) mortality while 100% recovery was found in patients with power grade 4 and 5 at the time of admission. The G.l. haemorrhage was associated with 5% of patients but mortality was significantly high (100%) in these patients. The level of consciousness of grade / was highest (34%) while mortality was significantly high (100%) in the patients admitted with grade 3 level of consciousness. The recovery was significantly high (92.9%) in the patients admitted with grade 'O’ level of consciousnes

Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland

Bibliography: pages 45-55.Eleven gravity cores from the continental margin off Eire and Land's End (SW England) were examined and found to document the major trends of the Late Pleistocene climate. Several stratigraphic indicators; - carbonate content, sediment texture, grain size, composition, nature of terrigenous components, ice-rafted debris and foraminiferal diversity were examined and show that the glacial history of the study area can be closely correlated with the palaeoclimatic evolution of the adjacent European shelf. Sediments deposited during Late Pleistocene glacial conditions show the following characteristics when compared to the surface sediments deposited under Holocene interglacial conditions: an increase in the quantity of ice-rafted debris and percentage of mica, and a notable increase in the degree of frosting and pitting of the quartz grains. Overall grain size was finer resulting in a silty sediment package. Sedimentologically the cores fall into two groups (1 and 2). The major difference being that Group 1 (located on the Pendragon Escarpment) received increased quantities of fine silts from a 'shelf spill-over' mechanism operating on the Fastnet and Western Approaches Basins, during glacial regressions. All sediment samples displayed polymodal characteristics reflecting the interaction of several different physical processes e.g. ice-rafting, contour currents etc. Striking variations in the populations of planktonic foraminifera were noted, alternating between Arctic and Sub-Arctic assemblages, reflecting the waxing and waning of glacial activity. The coccolith-carbonate minima correlate with the Arctic-fauna maxima and the ¹⁸O/¹⁶O maxima of the oxygen-isotope curves. Foraminiferal-test analysis (ratio of whole foraminifera fragmented foraminifera) revealed that no correlation existed with any of the other parameters analysed. However, the cores were severely affected by the presence of bottom currents which were strong enough to remove the fragmented tests. Parallellaminated contourites and evidence of erosion were noted in all cores. Ten cores penetrated sediments deposited during the last glacial maximum of 20,000 B.P - 18,000 B.P. near the 75cm depth mark (Core 1865 was too short to reach such sediments). However sediments reflecting the 11,000 B.P glacial readvance, detected at around the 25cm mark, were not as clearly represented. Bioturbation has smoothed the climatic record throughout the lengths of these cores and has also suppressed the high-frequency oscillations (<10³ B.P)

Deglaciation of the Reisa Valley, Northern Norway, and Studies of Glacial Deposits and Dispersal Processes

Durante el retroceso glacial en el area del Valle de Reisa, los principales valles estuvieron ocupados por glaciares marginales que descendían hacia los fiordos. Se han podido detectar cuatro momentos separados de avance o estancamiento de los hielos, marcados por las morrenas marginales correspondientes a acumulaciones del frente glacial. Las morrenas más antiguas, morrenas de Reisatjord, son correlacionables con las morrenas de Ra del Dryas reciente. Las morrenas más jóvenes son de edad Preboreal, 9900-9800 B.P., 9700-9500 B.P. y 9400 $ 250 B.P. respectivamente. Posteriormente el retroceso glacial se caracterizó por los efectos de una gran actividad fluvioglacial. A lo largo del límite entre Finlandia y Noruega, al W del Valle de Reisa, el drenaje del agua de fusión estuvo dirigido por el hielo hacia el Este, más o menos transversalmente a la dirección Norte del movimiento del hielo. Una serie de canales de desagüe cmzaban las divisorias. Los estudios realizados sobre sedimentos de estos depósitos proglaciales muestran una génesis y procedencia complejos. Las composiciones litológica y geoquímica son distintas, generalmente, de la:; de los tills. La composición del till presenta también variaciones verticales. La parte más profunda del till, en contacto con la roca, generalmente es de procedencia local. En las regiones interiores en la parte alta del till predomina el material transportado distancias superiores a los 5 Km. en la parte central de la cuenca de drenaje de Reisa el recubrimiento de till es más delgado y los depósitos glaciales tienen un origen más local. El till sólo contiene un 50% del contenido original en granito rojo después de 5-6 km. de transporte

Síntese da história da Evolução Holocénica do Parque Nacional de Doñana (Espanha): evolução paleoambiental, influência climática, eventos energéticos extremos e registro de foraminíferos

O presente trabalho tem como objectivo realizar uma síntese da evolução paleogeográfica do Parque Nacional de Doñana, através de uma compilação da informação previamente publicada sobre o assunto, incluindo a descrição geral das variações climáticas tardi-holocénicas na Península Ibérica. Dados sedimentológicos e de microfauna de dois cores e o registo histórico de eventos energéticos extremos em Portugal e Espanha são igualmente combinados e discutidos no que diz respeito ao reconhecimento dos intervalos climáticos e eventos tsunamigénicos. Os resultados mostram que a evolução paleogeográfica do Parque Nacional de Doñana parece certamente ligada às mudanças climáticas e à ocorrência de eventos energéticos extremos como observado para o tsunami de 2168-2159 B.P., durante o período Sub-Atlântico