The natural remanent magnetization of sediment cores from the Beaufort Sea

1977 ◽  
Vol 14 (9) ◽  
pp. 2007-2012 ◽  
Author(s):  
G. Vilks ◽  
J. M. Hall ◽  
David J. W. Piper
Keyword(s):  
Remanent Magnetization ◽  
Sediment Cores ◽  
Beaufort Sea ◽  
Natural Remanent Magnetization ◽  
Reasonable Assumption ◽  
High Deposition Rate ◽  
Areal Extent ◽  
Fine Silt ◽  
Geomagnetic Excursion ◽  
Dating Method

Two sediment cores collected from the continental slope of the southeastern Beaufort Sea show zones of stable shallow geomagnetic inclination at close to 0° in contrast with the dipole value of 80°. Although the cores were taken 60 km apart, the shallow inclination sections are sufficiently similar in form to be useful as potential correlation horizons, on the reasonable assumption that the same geomagnetic excursion is recorded in both cores.The cores consist of silt and clay, showing fine silt–clay laminae or structureless mud on X-radiographs. Except for the surface 2.5 m of core 810, foraminifera are sparse everywhere.The 14C dates for total organic carbon place the recorded paleomagnetic event at between 10 000 and 40 000 years BP. According to paleontologic evidence, the event took place between 6 000 and 16 000 years BP. The later dating method is considered to be more reliable. Sediment cores from other high deposition rate areas need to be examined paleomagnetically to determine the areal extent of this Beaufort Sea geomagnetic excursion.

scholarly journals Paleomagnetic secular variation for a 21,000-year sediment sequence from Cascade Lake, north-central Brooks Range, Arctic Alaska

2021 ◽  
Author(s):  
Douglas P. Steen ◽  
Joseph S. Stoner ◽  
Jason P. Briner ◽  
Darrell S. Kaufman
Keyword(s):  
Secular Variation ◽  
Remanent Magnetization ◽  
Sediment Cores ◽  
Natural Remanent Magnetization ◽  
Companion Paper ◽  
Angular Deviation ◽  
Arctic Alaska ◽  
Geomagnetic Field Models ◽  
Paleomagnetic Secular Variation ◽  
Radiometric Ages

Abstract. Two > 5-m-long sediment cores from Cascade Lake (68.38° N, 154.60° W), Arctic Alaska, were analyzed to quantify their paleomagnetic properties over the past 21,000 years. Alternating-field demagnetization of the natural remanent magnetization, anhysteretic remanent magnetization, isothermal remanent magnetization, and hysteresis experiments reveal a strong, well-defined characteristic remanent magnetization carried by a low coercivity magnetic component that increases up core. Maximum angular deviation values average < 2°, and average inclination values are within 4° of the geocentric axial dipole prediction. Radiometric ages based on 210Pb and 14C were used to correlate the major inclination features of the resulting paleomagnetic secular variation (PSV) record with those of other regional PSV records, including two geomagnetic field models and the longer series from Burial Lake, located 200 km to the west. Following around 6 ka (cal BP), the ages of PSV fluctuations in Cascade Lake begin to diverge from those of the regional records, reaching a maximum offset of about 2000 years at around 4 ka. Several correlated cryptotephra ages from this section (reported in a companion paper by Davies et al., this volume) support the regional PSV-based chronology and indicate that some of the 14C ages at Cascade Lake are variably too old.

Near East Paleomagnetic Secular Variation Recorded in Sediments from the Sea of Galilee (Lake Kinneret)

1985 ◽  
Vol 23 (2) ◽  
pp. 175-188 ◽  
Author(s):  
R. Thompson ◽  
G. M. Turner ◽  
M. Stiller ◽  
A. Kaufman
Keyword(s):  
Magnetic Susceptibility ◽  
Secular Variation ◽  
Similar Pattern ◽  
Remanent Magnetization ◽  
Sediment Cores ◽  
Natural Remanent Magnetization ◽  
Lake Kinneret ◽  
Carbonate Content ◽  
Magnetization Intensity ◽  
Olive Pollen

Paleomagnetic records of declination and inclination from sediments recovered from the bed of Lake Kinneret (32.4°N, 35.7°E) have been dated by radiocarbon techniques. The sediments span the last 5000 yr. The changes in inclination down the sediment cores are more pronounced than the declination fluctuations and are repeatable between the three coring sites, which are several kilometers apart. Magnetic susceptibility logs display 13 maxima in the 5-m-long sequences, with a pronounced susceptibility minimum about 1000 yr B.P. Many of the susceptibility maxima and minima can be easily correlated between coring sites and are shown to be dominantly related to changes in sediment carbonate content. The natural remanent magnetization intensity follows a similar pattern to that of susceptibility, and the natural remanence of the Kinneret sediments is presumed to reside in detrital magnetite grains carried into the lake by the river Jordan from the basalt-rich bedrock of the rift floor and the Golan Heights. The 14C chronology is strongly supported by a pollen study in which pronounced changes in the proportion of olive pollen were interpreted as being due to extensive cultivation of olives around Galilee in the Hellenistic and Byzantine periods. The Kinneret paleosecular variation records, if accurately dated, point to a complex spatial pattern of Holocene secular variation with significant variations over distances as small as 1000–2000 km.

Multi-proxy study of the Cretaceous-Paleogene (K-Pg) boundary in deep-sea turbiditic sediments in the Uzgruň section (Outer Flysch Carpathians, Czech Republic)

2021 ◽  
Author(s):  
Šimon Kdýr ◽  
Tiiu Elbra ◽  
Miroslav Bubík ◽  
Petr Schnabl ◽  
Lilian Švábenická
Keyword(s):  
Magnetic Susceptibility ◽  
Czech Republic ◽  
Detection Limit ◽  
Remanent Magnetization ◽  
Magnetic Particles ◽  
Principal Component ◽  
Natural Remanent Magnetization ◽  
Ongoing Research ◽  
Small Stream ◽  
Magnetic Methods

&lt;p&gt;The composite profile, with 4 studied sections, is located near the Uzgru&amp;#328; village (Czech Republic) next to a small stream. The profile is composed of Late Maastrichtian to Palaeocene flysch sediments and the K-Pg boundary is set in claystones within this turbiditic setting. Ongoing research of local paleoenvironment and stratigraphy is based on paleo- and rock-magnetic methods, micropaleontology and geochemistry to obtain more detailed view of the local situation during the K-Pg extinction event. Based on biostratigraphy, two dinocyst zones (Bub&amp;#237;k et al., 2002): Palynodium grallator and Carpatella cornuta (first occurrence in the Danian), two calcareous nannofossil zones in the Upper Maastrichtian, and the agglutinated foraminifer zone Rzehakina fissistomata in the Paleogene were distinguished. Biostratigraphic data support the K-Pg boundary interval. The uppermost Maastrichtian is indicated by nannofossil species Micula prinsii, UC26d&lt;sup&gt;TP&lt;/sup&gt; zone. Basal Paleogene non-calcareous strata contain dinocyst Carpatella cornuta and agglutinated foraminifers of Rzehakina fissistomata zone. The presence of low-latitude nannofossil taxa M. prinsii and Ceratolithoides kamptneri show input of warm waters during the uppermost Maastrichtian. Several rock-magnetic methods, such as acquisition of Isothermal remanent magnetization (IRM), acquisition of Anhysteretic remanent magnetization (ARM), Anisotropy of magnetic susceptibility (AMS), Field dependence of magnetic susceptibility (HD) and Frequency dependence of magnetic susceptibility (FD), were applied to estimate behaviour and origin of magnetic particles. Natural remanent magnetization (NRM) values of samples range from 0.09 to 2.48 mA/m. Volume normalized magnetic susceptibility (MS) show values from 130 up to 1197 SI*10-6. There is no increase observed in MS across stratigraphic boundary due to turbiditic evolution of sediment. Due to character of sediments, we applied alternating field (AF) demagnetization and used principal component analysis (PCA; Kirschvink, 1980) for estimation of characteristic remanent component. Most of the K/Pg sections worldwide have well documented Iridium anomaly. In Uzgru&amp;#328;, the preliminary results show that although the values are not as pronounced, the Ir at K-Pg boundary is still higher than in surrounding sediments. For tracing of Deccan traps effect we plan to apply mercury (Hg)/total organic carbon (TOC) stratigraphy. TOC content of 20 pilot samples is low, but not under detection limit of the instrumentation (mean value 0.92 wt%). One sample reached value 4.41 wt% of TOC. Sulphur contents are reaching 1 wt%, but several samples were under detection limit of the instrumentation. Sulphur concentrations suggest more reduction conditions of burial.&lt;/p&gt;&lt;p&gt;Current research is supported by Czech Science Foundation project no. 19-07516S and is in accordance with research plan no. RVO67985831.&lt;/p&gt;&lt;p&gt;Bub&amp;#237;k, M., Adamov&amp;#225;, M., B&amp;#261;k, M., Franc&amp;#367;, J., Gedl, P., Mikul&amp;#225;&amp;#353;, R., &amp;#352;v&amp;#225;benick&amp;#225;, L., &amp; Uchman, A. (2002). V&amp;#253;sledky v&amp;#253;zkumu hranice k&amp;#345;&amp;#237;da/terci&amp;#233;r v magursk&amp;#233;m fly&amp;#353;i u Uzgrun&amp;#283;. Geologick&amp;#233; v&amp;#253;zkumy na Morav&amp;#283; a ve Slezsku, 9, 18&amp;#8211;22&lt;/p&gt;&lt;p&gt;L. Kirschvink (1980), The least-squares line and plane and the analysis of palaeomagnetic data,&amp;#160;Geophysical Journal International, 62(3), 699&amp;#8211;718,&amp;#160;https://doi.org/10.1111/j.1365-246X.1980.tb02601.x&lt;/p&gt;

scholarly journals Post-Depositional Fluid Flow in Jurassic Sandstones of the Uncompahgre Uplift: Insights From Magnetic Fabrics

2020 ◽  
Vol 8 ◽  
Author(s):  
John I. Ejembi ◽  
Eric C. Ferré ◽  
Sara Satolli ◽  
Sarah A. Friedman
Keyword(s):  
Fluid Flow ◽  
Remanent Magnetization ◽  
Magnetic Hysteresis ◽  
Natural Remanent Magnetization ◽  
Upper Jurassic ◽  
Hydrocarbon Exploration ◽  
Reservoir Rock ◽  
Magnetic Fabrics ◽  
Deformation Processes ◽  
Carbonate Formations

The anisotropy of magnetic susceptibility (AMS) in sedimentary rocks results from depositional, diagenetic, syn- and post-sedimentary processes that affect magnetic grains. Some studies have also shown the potential role played by post-depositional fluid flow in detrital and carbonate formations. Here we present a new case study of Middle-Upper Jurassic sandstones where secondary iron oxides, precipitated from fluids that migrated through pores, give rise to the AMS. These sandstones are well exposed in the Uncompahgre Uplift region of the Central Colorado Trough, Colorado. The magnetic foliation of these undeformed, subhorizontal strata consistently strike NE-SW over a large distance with an average 45° dip to the SE. This steep AMS fabric is oblique with respect to the regional subhorizontal bedding and therefore does not reflect the primary sedimentary fabric. Also, outcrop-scale and microscopic observations show a lack of post-depositional plastic (undulose extinction) or pressure-solution (stylolites) deformation microstructures in these sandstones, hence precluding a tectonic origin. The combination of magnetic hysteresis, isothermal remanent magnetization, and thermal demagnetization of the natural remanent magnetization indicate that these rocks carry a chemical remanent magnetization born primarily by hematite and goethite. High-field magnetic hysteresis and electron microscopy indicate that detrital magnetite and authigenic hematite are the main contributors to the AMS. These results show that post-depositional iron remobilization through these porous sandstones took place due to the action of percolating fluids which may have started as early as Late Cretaceous along with the Uncompahgre Uplift. The AMS fabric of porous sandstones does not systematically represent depositional or deformation processes, and caution is urged in the interpretation of magnetic fabrics in these types of reservoir rock. Conversely, understanding these fabrics may advance our knowledge of fluid flow in porous sandstones and may have applications in hydrocarbon exploration.

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