3000-Year paleoseismological record from the region of the 1988 Saguenay, Quebec, earthquake

1998 ◽  
Vol 88 (5) ◽  
pp. 1198-1203
Author(s):  
Ronald Doig
Keyword(s):  
Active Region ◽  
Lake Sediment ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Recurrence Interval ◽  
Pattern Match ◽  
Local Origin ◽  
Organic Rich Sediment

Abstract The 1988, magnitude mb 5.9 (mbLg 6.5) Saguenay, Quebec, earthquake occurred in a region considered to be aseismic, but the epicenter was less than 100 km northwest of the seismically active region of Charlevoix. Lake sediment cores representing some 3000 yr of sediment accumulation contain abnormal silt layers attributed to seismic shaking events prior to the 1988 earthquake. The layers are formed by the relatively rapid settling of the silt portion of the seismically resuspended organic-rich sediment. Cores were obtained over a distance of 120 km, perpendicular to the Saguenay graben structure. Several silt layers are much thicker and more widely distributed than the effect of the 1988 earthquake and are comparable to those observed at Charlevoix that were produced by magnitude 6 to 7 events. The silting events do not correlate between the sampled lakes nor does the pattern match that at Charlevoix, so that the shaking events are interpreted to be of local origin. The recurrence interval for magnitude ≧6 earthquakes ranges from 350 to 1000 yr, in contrast to the roughly 75-yr historical recurrence of earthquakes of magnitude greater than 6 at Charlevoix.

Reconstructing the Rate of Accumulation of Lake Sediment: The Effect of Sediment Focusing

1975 ◽  
Vol 5 (4) ◽  
pp. 541-550 ◽  
Author(s):  
John T. Lehman
Keyword(s):  
Temporal Variation ◽  
Lake Sediment ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Maximum Depth ◽  
Accumulation Rates ◽  
Sediment Focusing ◽  
Regional History ◽  
Rate Of Accumulation

Use of accumulation rates of pollen or minerals to infer regional history is complicated by nonuniform deposition of lake sediment. Sediment focusing, direction of sediment to the deepest part of a basin, can introduce a discrepancy between changes in accumulation rates measured directly from sediment cores and actual changes in influx of sediment or pollen to a lake. This difference depends on values and temporal variation of the ratio of mean depth to maximum depth in a basin as it fills. Several models of sediment accumulation show how measurements from a single core can be transformed to yield basinwide influx rates, and how the distortion due to sediment focusing can be assessed. Basins shaped like hyperboloids or frustums may introduce much greater distortions than basins conforming to ellipsoid or sinusoid shapes.

Pigment Preservation in Lake Sediments: A Comparison of Sedimentary Environments in Trout Lake, Wisconsin

1991 ◽  
Vol 48 (3) ◽  
pp. 472-486 ◽  
Author(s):  
James P. Hurley ◽  
David E. Armstrong
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Sediment Surface ◽  
Water Interface ◽  
Sedimentary Pigments ◽  
Sedimentary Environments ◽  
Trout Lake ◽  
Secondary Carotenoids ◽  
Β Carotene

Fluxes and concentrations of a phorbins and major algal carotenoids were quantified in sediment trap material and sediment cores from two basins of Trout Lake, Wisconsin (TrDH and TrAB). The basins were chosen to contrast the influence of oxygen content at the sediment–water interface (TrDH, oxic and TrAB, reducing), sediment accumulation rate, and focusing. Pigment diagenesis occurred in both basins, but transformations and destruction were more extensive in TrDH. Although untransformed chlorophyll a was the major phorbin deposited at the sediment surface of both basins (51–64 mol%), pigment destruction, coupled with transition to pheophytin, accounted for substantial losses, especially in oxic TrDH sediments. Fucoxanthin, peridinin, and diadinoxanthin, despite representing > 70% of the deposited carotenoid flux, were substantially degraded or transformed in both basins. However, preservation was relatively high for secondary carotenoids, such as diatoxanthin and β-carotene, and for a major cryptomonad pigment, alloxanthin. Residual profiles in sediments show that pigment sedimentation from the epilimnion and accumulation in the permanent sediments are not directly related and that diagenesis must be considered in interpreting sedimentary pigments.

The Toba Volcanic Event and Interstadial/Stadial Climates at the Marine Isotopic Stage 5 to 4 Transition in the Northern Indian Ocean

2002 ◽  
Vol 57 (1) ◽  
pp. 22-31 ◽  
Author(s):  
Hartmut Schulz ◽  
Kay-Christian Emeis ◽  
Helmut Erlenkeuser ◽  
Ulrich von Rad ◽  
Christian Rolf
Keyword(s):  
Arabian Sea ◽  
Water Productivity ◽  
Ice Core ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Sediment Supply ◽  
Volcanic Event ◽  
Additional Support ◽  
Marine Isotope Stage 5 ◽  
A Minor

AbstractThe Toba volcanic event, one of the largest eruptions during the Quaternary, is documented in marine sediment cores from the northeastern Arabian Sea. On the crest of the Murray Ridge and along the western Indian continental margin, we detected distinct concentration spikes and ash layers of rhyolithic volcanic shards near the marine isotope stage 5–4 boundary with the chemical composition of the “Youngest Toba Tuff.” Time series of the Uk′37-alkenone index, planktic foraminiferal species, magnetic susceptibility, and sediment accumulation rates from this interval show that the Toba event occurred between two warm periods lasting a few millennia. Using Toba as an instantaneous stratigraphic marker for correlation between the marine- and ice-core chronostratigraphies, these two Arabian Sea climatic events correspond to Greenland interstadials 20 and 19, respectively. Our data sets thus depict substantial interstadial/stadial fluctuations in sea-surface temperature and surface-water productivity. We show that variable terrigenous (eolian) sediment supply played a crucial role in transferring and preserving the productivity signal in the sediment record. Within the provided stratigraphic resolution of several decades to centennials, none of these proxies shows a particular impact of the Toba eruption. However, our results are additional support that Toba, despite its exceptional magnitude, had only a minor impact on the evolution of low-latitude monsoonal climate on centennial to millennial time scales.

The History of Human Impacts in the Clear Lake Watershed ( California) as Deduced from Lake Sediment Cores*

1999 ◽  
Author(s):  
Douglas Nelson ◽  
Alan Heyvaert ◽  
Laurent Meillier ◽  
Jae Kim ◽  
Xiaoping Li ◽  
...  
Keyword(s):  
Lake Sediment ◽  
Human Impacts ◽  
Sediment Cores ◽  
Clear Lake ◽  
History Of

scholarly journals 240+239Pu depositional signatures as a viable geochronological tool in the Amazon Basin

2017 ◽  
Vol 44 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Luciana M Sanders ◽  
Kathryn H Taffs ◽  
Debra Stokes ◽  
Alex Enrich-Prast ◽  
Christian J Sanders
Keyword(s):  
Amazon Basin ◽  
Environmental Science ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Recent Sediment ◽  
Floodplain Lake ◽  
Accumulation Rates ◽  
Amazon Floodplain ◽  
Dating Methods ◽  
Lead 210

AbstractAnthropogenic radionuclide signatures associated with nuclear testing are increasingly utilized in environmental science to explore recent sedimentation. In this study, we assess the suitability of Pu radioisotope analysis in floodplain lake environments in the Amazon Basin to form geochronologies during the 20thcentury. The240Pu +239Pu (240+239Pu) signatures in six sediment cores indicate sediment accumulation rates in the floodplain lakes of the major rivers; Amazon (2.3 mm year-1), Tapajos (10.2 and 2.4 mm year-1) and Madeira (3.4, 4.2 and 6.2 mm year-1). The results from this study show that240+239Pu fallout activities, and the well documented (240Pu/239Pu) atomic ratios of the above ground nuclear tests which began in the 1950’s, are sufficient and well preserved in Amazon floodplain lake sediments to infer chronologies. Lead-210 dating analyses in the same sediment cores produced comparable sediment accumulation rates at three of the six sites. The differences between dating methods may be attributed to the different time scale these dating methods represent and/or in the solubility between Pb and Pu along the sediment column. The geochronologies derived from the240+239Pu and210Pb dating methods outlined in this work are of interest to identify the effects of changing sediment accumulation rates during the previous century as a result of development, including deforestation, along the Amazon Basin which increased towards the middle of the 20thcentury. This study shows that Pu dating provides a viable alternative geochronology tool for recent sediment accumulation (previous ~60 years) along the Amazon Basin.

Sign in / Sign up

Export Citation Format

Share Document