Palynological studies of the late Maastrichtian infratrappean and intertrappean sedimentary beds from various stratigraphic levels in the Deccan continental flood basalt of the Nand-Dongargaon Basin in central India show that infratrappean sediments (Maastrichtian C30n-C29r) are characterized by gymnosperm ( Araucariacites , Classopollis , Cycadopites , Podocarpidites ) and angiosperm ( Cretacaeiporites , Compositoipollenites , Graminidites , Longapertites , Palmaepollenites ) palynomorphs. A distinct floral turnover is observed in intertrappean sediments with the initiation of volcanic activity in the basin. At the lowest stratigraphic level, the earliest floral change is recorded by the appearance of angiosperm-pteridophyte–dominated association ( Aquilapollenites , Azolla , Gabonisporis , Tricolpites , Triporopollenites , and Normapolles group pollen) and the appearance of peridinoid dinoflagellates. At higher stratigraphic levels in C29r, this palynofloral association continues with the appearance of new forms, such as Scabrastephanocolpites spp., Scollardia conferta , and Triporopollenites cracentis . A sharp decline in diversity of titanosauriform-abelisaurid–dominated dinosaurian fauna is also observed with the onset of Deccan volcanic activity. At this time, out of at least eight dinosaur species, only a single taxon of titanosauriform dinosaurs survived the onset of volcanism. This suggests that the floral change and decreased dinosaur diversity are strongly linked with the initiation of Deccan volcanism in C29r in India. The peak eruption of this volcanic phase resulted in the Deccan's largest volume of lava flows, which played a significant role in the global mass extinction at the Cretaceous-Paleogene boundary.

Sn-rich particles, Ni-rich particles, and cosmic spherules are found together at four discrete stratigraphic levels within the 362–360 m depth interval of the Greenland Ice Sheet Project 2 (GISP2) ice core (72.6°N, 38.5°W, elevation: 3203 m). Using a previously derived calendar-year time scale, these particles span a time of increased dust loading of Earth's atmosphere between A.D. 533 and 540. The Sn-rich and Ni-rich particles contain an average of 10–11 wt% C. Their high C contents coupled with local enrichments in the volatile elements I, Zn, Cu, and Xe suggest a cometary source for the dust. The late spring timing of extraterrestrial input best matches the Eta Aquarid meteor shower associated with comet 1P/Halley. An increased flux of cometary dust might explain a modest climate downturn in A.D. 533. Both cometary dust and volcanic sulfate probably contributed to the profound global dimming during A.D. 536 and 537 but may be insufficient sources of fine aerosols. We found tropical marine microfossils and aerosol-sized CaCO 3 particles at the end A.D. 535–start A.D. 536 level that we attribute to a low-latitude explosion in the ocean. This additional source of dust is probably needed to explain the solar dimming during A.D. 536 and 537. Although there has been no extinction documented at A.D. 536, our results are relevant because mass extinctions may also have multiple drivers. Detailed examinations of fine particles at and near extinction horizons can help to determine the relative contributions of cosmic and volcanic drivers to mass extinctions.

Bear Lake is a large alkaline lake on a high plateau on the Utah-Idaho border. The Bear River was partly diverted into the lake in the early twentieth century so that Bear Lake could serve as a reservoir to supply water for hydropower and irrigation downstream, which continues today. The northern Rocky Mountain region is within the belt of the strongest of the westerly winds that transport moisture during the winter and spring over coastal mountain ranges and into the Great Basin and Rocky Mountains. As a result of this dominant winter precipitation pattern, most of the water entering the lake is from snowmelt, but with net evaporation. The dominant solutes in the lake water are Ca 2+ , Mg 2+ , and HCO 3 2‒ , derived from Paleozoic carbonate rocks in the Bear River Range west of the lake. The lake is saturated with calcite, aragonite, and dolomite at all depths, and produces vast amounts of carbonate minerals. The chemistry of the lake has changed considerably over the past 100 years as a result of the diversion of Bear River. The net effect of the diversion was to dilute the lake water, especially the Mg 2+ concentration. Bear Lake is oligotrophic and coprecipitation of phosphate with CaCO 3 helps to keep productivity low. However, algal growth is colimited by nitrogen availability. Phytoplankton densities are low, with a mean summer chlorophyll a concentration of 0.4 mg L ‒1 . Phytoplankton are dominated by diatoms, but they have not been studied extensively (but see Moser and Kimball, this volume). Zooplankton densities usually are low (<10 L ‒1 ) and highly seasonal, dominated by calanoid copepods and cladocera. Benthic invertebrate densities are extremely low; chironomid larvae are dominant at depths <30 m, and are partially replaced with ostracodes and oligochaetes in deeper water. The ostracode species in water depths >10 m are all endemic. Bear Lake has 13 species of fish, four of which are endemic.

Changes in diatom fossil assemblages from lake sediment cores indicate variations in hydrologic and climatic conditions at Bear Lake (Utah-Idaho) during the late glacial and Holocene. From 19.1 to 13.8 cal ka there is an absence of well-preserved diatoms because prolonged ice cover and increased turbidity from glacier-fed Bear River reduced light and limited diatom growth. The first well-preserved diatoms appear at 13.8 cal ka. Results of principal components analysis (PCA) of the fossil diatom assemblages from 13.8 cal ka to the present track changes related to fluctuations of river inputs and variations of lake levels. Diatom abundance data indicate that the hydrologic balance between 13.8 and 7.6 cal ka is strongly tied to river inputs, whereas after 7.6 cal ka the hydrologic balance is more influenced by changes in lake evaporation. Wet conditions maintained high river inputs from 13.8 to 10.8 cal ka and from 9.2 to 7.6 cal ka, with a dry interval between 10.8 and 9.2 cal ka. After 9.2 cal ka until 2.9 cal ka lake levels were high except for two periods, one between 7.6 and 5.8 cal ka and one between 4.3 and 3.8 cal ka, as a result of decreased effective moisture. After 2.9 cal ka, fossil diatom assemblages suggest drier conditions until 1.6 cal ka to the present, when fragments of large, pennate diatoms appear, possibly the result of a rapid lake transgression. Although similarities exist between the Bear Lake records and other western hydrologic and climatic records, the covariations are not strong. Our data suggest that climatic regimes at Bear Lake have changed frequently over time, perhaps as a consequence of the position of several important climatic boundaries near Bear Lake.

A continuous, 120-m-long core (BL00-1) from Bear Lake, Utah and Idaho, contains evidence of hydrologic and environmental change over the last two glacial-interglacial cycles. The core was taken at 41.95°N, 111.31°W, near the depocenter of the 60-m-deep, spring-fed, alkaline lake, where carbonate-bearing sediment has accumulated continuously. Chronological control is poor but indicates an average sedimentation rate of 0.54 mm yr ‒1 . Analyses have been completed at multi-centennial to millennial scales, including (in order of decreasing temporal resolution) sediment magnetic properties, oxygen and carbon isotopes on bulk-sediment carbonate, organic- and inorganic- carbon contents, palynology; mineralogy (X-ray diffraction), strontium isotopes on bulk carbonate, ostracode taxonomy, oxygen and carbon isotopes on ostracodes, and diatom assemblages. Massive silty clay and marl constitute most of the core, with variable carbonate content (average = 31 ± 19%) and oxygen-isotopic values (δ 18 O ranging from ‒18‰ to ‒5‰ in bulk carbonate). These variations, as well as fluctuations of biological indicators, reflect changes in the water and sediment discharged from the glaciated headwaters of the dominant tributary, Bear River, and the processes that influenced sediment delivery to the core site, including lake-level changes. Although its influence has varied, Bear River has remained a tributary to Bear Lake during most of the last quarter-million years. The lake disconnected from the river and, except for a few brief excursions, retracted into a topographically closed basin during global interglaciations (during parts of marine isotope stages 7, 5, and 1). These intervals contain up to 80% endogenic aragonite with high δ 18 O values (average = ‒5.8 ± 1.7‰), indicative of strongly evaporitic conditions. Interglacial intervals also are dominated by small, benthic/tychoplanktic fragilarioid species indicative of reduced habitat availability associated with low lake levels, and they contain increased high-desert shrub and Juniperus pollen and decreased forest and forest-woodland pollen. The 87 Sr/ 86 Sr values (>0.7100) also increase, and the ratio of quartz to dolomite decreases, as expected in the absence of Bear River inflow. The changing paleoenvironments inferred from BL00-1 generally are consistent with other regional and global records of glacial-interglacial fluctuations; the diversity of paleoenvironmental conditions inferred from BL00-1 also reflects the influence of catchment-scale processes.

Neogene sediments in a structural and geomorphic high in the southwestern Honey Lake basin represent lacustrine deposition from 3.7 to 2.9 Ma, interrupted once by a significant lowstand. Tephras in the upper section are 3.26 Ma and 3.06 Ma. A thick debris-flow bed, truncated by an erosional surface and overlain concordantly by a thin interval of subaerial sediments, is evidence for lake-level fall at ca. 3.4 Ma. The dominant structure is a broad east-southeast–plunging anticline cut by several sets of faults. These include northwest-striking dextral and northeast-striking sinistral strike-slip faults and a conjugate set of west-northwest–striking thrust faults; all are consistent with north-south shortening. Mutually crosscutting relationships between faults, and tilt fanning of the dextral faults, indicate that tightening of the anticline was synchronous with faulting. A Quaternary strand of the dextral Honey Lake fault crops out near the northern end of the exposure, suggesting that the cause of the local shortening and uplift was a contractional stepover between two strands of the Honey Lake fault. The Neogene section limits this faulting to some time after 2.9 Ma. The Honey Lake basin lies at the intersection of the Walker Lane with the Sierran frontal fault system. Although the timing of tectonic disruption was roughly consistent with passage of the triple junction to the west and with uplift and exhumation of several nearby basins, the described deformation seems to be directly related to dextral faulting, dating the propagation of a strand of the Honey Lake fault through the southwestern Honey Lake basin.

Scanning electron microscopy (SEM) of insect and plant fossils in the lacustrine shales of the Eocene Florissant Formation of Florissant, Colorado, was used to investigate the mechanisms of fossil preservation. The fossiliferous Florissant “paper shales” are composed of thin laminae of diatomite that form couplets with alternating smectitic clay laminae. The millimeter-scale sedimentary couplets may preserve an episodic record of sedimentation and are interbedded with less frequent, coarser volcaniclastic layers. The insect and plant fossils are associated with biofilms of extracellular polymeric substances (EPS) secreted by diatoms. The preserved organisms are entangled in the diatom aggregates coated with the EPS biofilm. We suggest that decomposition of the organisms was arrested during sedimentation and burial by the protective nature of the mucus covering, the properties of which limited the actions of bacteria and grazers and may have enhanced fossilization. A novel contribution of the study is a demonstration that this mechanism of exceptional preservation is also common at other similar lacustrine fossil sites, as supported by a further SEM analysis of insect and plant fossils from other Cenozoic lake deposits formed in environments comparable to the Floris-sant Formation. The deposits include the Oligocene shale at Canyon Ferry, Montana; the Miocene Savage Canyon Formation, Stewart Valley, Nevada; and the Miocene Shanwang Beds of Shandong Province in northeast China. In addition, cultures of diatomaceous biofilms, grown in the laboratory display morphological features identical to those of the fossil diatomaceous biofilms. Our contribution indicates the significance of biofilms in fossil preservation at Florissant and other deposits.

The Baltic sea-level oscillations in the Atlantic and Subboreal periods are known from sedimentary records on slightly uplifting coasts in Denmark and southern Sweden (e.g., Berglund, 1971 ; Digerfeldt, 1975 ). The periodicity of those oscillations is in close correlation with recent data on climatic cycles with a periodicity of 1500, 1000, and 550 yr (e.g., Stuiver et al., 1995 ; Chapman and Shackleton, 2000 ). The effects of regional eustatic oscillations in the coastal area of the Southern Baltic are poorly known because of the slightly subsiding coast and the magnitude of barographic and storm surges, which are larger than those of eustatic oscillations. To solve these problems, sediment sequences on the western coasts of the Puck Lagoon (northwestern part of the Gulf of Gdańsk) were investigated. Recent vertical movements of Earth's crust are ∼0.0 to −0.5 mm/yr. According to 14 C datings, pollen and diatom analyses, the earliest marine influences occurred in the Middle Atlantic period, while at the end of the Atlantic period almost all of the area was occupied by brackish waters ( Kramarska et al., 1995 ; Uścinowicz and Miotk-Szpiganowicz, 2003 ). Several sediment cores were taken along the western coast of the Puck Lagoon. Ordinates of the collected cores were geodetically determined to ± 1 cm relative to the mean sea level. Peat, plant remains, and marine shells (64 samples) were dated using the classic 14 C and AMS (accelerator mass spectrometry) methods. The plot showing the altitude of peat and marine mollusk shells versus their radiocarbon age shows that during the Subboreal and Subatlantic periods water levels in the Puck Lagoon were as follows: 5 ka B.P.—2.8 m, 4 ka B.P.—1.8–1.9 m, 3 ka B.P.—1.3–1.4 m, 2 ka B.P.—0.8–0.9 m, and 1 ka B.P.—0.4–0.5 m b.s.l. The rises in sea level during the Subboreal and Subatlantic periods may have been cyclical and related to climatic oscillations. The periodicity of water-level changes was ca. 1000 yr and their amplitude was ∼0.3–0.5 m. This is also confirmed by pollen and diatom analyses.

Las Tablas de Daimiel, Spain, is one of the scarce, freshwater wetlands areas still preserved in southern Europe. The wetland is fed by surface and groundwater. We studied the Quaternary sedimentary record of Las Tablas in a drill hole that penetrated 38.5 m of shallow-lake and fluvial deposits. Differences in the dominantly micritic muds indicate three main stages of development. In the lowest stage, unit A, (Lower? to Middle Pleistocene) the slightly saline wetland developed under a relatively arid climate that favored slow flow movement of the fluvial system and the disconnection of the ponded areas. In the intermediate stage, unit B, (Middle to Upper Pleistocene) extensive peat developed during wetter conditions. Biosiliceous sediments (diatoms and sponge spicules) also accumulated in this swampy setting. In the latter stage, unit C, (Upper Pleistocene to Holocene) palustrine carbonates formed in a freshwater environment with desiccation events, followed by fluvial reworking of the lake margins. Lithification of these deposits was relatively fast (<10,000 yr). The studies of the core, including mineralogy, petrography, stables isotopes, and pollen analyses, indicate that these sediments are similar to those of ancient palustrine sequences. Therefore, Las Tablas can be considered as a recent analogue for freshwater palustrine systems that have no marine influence. These systems are very sensitive to changes in climate or base level, and their study is needed to better understand the terrestrial sedimentary record. Study is needed also to determine how to preserve these wetlands. Las Tablas de Daimiel constituyen uno de los escasos humedales de agua dulce que aún se conservan en el sur de Europa, concretamente en España. El humedal está abastecido por aguas superficiales y subterráneas. El registro sedimentario Cuaternario de Las Tablas, se ha estudiado mediante un sondeo en el que se cortaron 38.5 m de depósitos lacustres someros y fluviales, esencialmente carbonatos micríticos. Las características de los sedimentos permiten diferenciar tres principales etapas de sedimentación. En la primera etapa, unidad A, (Pleistoceno Inferior? a Medio) el humedal era ligeramente salino y se desarrolló bajo un clima relativamente árido que favoreció el flujo más lento del sistema fluvial, permitiendo la desconexión de las zonas encharcadas. En la etapa intermedia, unidad B, (Pleistoceno Medio a Superior) el amplio desarrollo de turberas indica condiciones más húmedas, en las que dentro de las áreas pantanosas también se depositaron sedimentos biosilíceos (diatomeas y espículas de esponjas). En la última etapa, unidad C, (Pleistoceno Superior a Holoceno) los sedimentos característicos son carbonatos palustres formados en un ambiente de agua dulce con eventos de desecación seguidos de posterior retrabajamiento de los márgenes lacustres por canales fluviales. La litificación de estos depósitos fue relativamente rápida (<10000 años). El estudio llevado a cabo en el sondeo (mineralogía, petrografía, isótopos estables, análisis polínicos) indica que estos sedimentos son similares a las secuencias palustres del registro geológico. Por tanto, Las Tablas de Daimiel pueden considerarse como un análogo reciente para sistemas palustres de agua dulce que no tengan influencia marina. Estos sistemas son muy sensibles a cambios climáticos y/o del nivel de base, por lo que su estudio es necesario para conocer mejor el registro sedimentario continental, pero también para preservar estos humedales.