DOI: 10.25921/9yjq-rp17
title: NOAA/WDS Paleoclimatology - Arctic Alaskan Margin Holocene Geomagnetic Data

description: Two long Holocene piston cores (HLY0501-06JPC and -08JPC; herein after referred to as 6JPC and 8JPC) were raised from high sediment accumulation areas in the Arctic Alaskan margin in order to reconstruct the millennial- to centennial-scale behavior of Earth's magnetic field and to better constrain the regional chronostratigraphy of the Western Arctic. Paleomagnetic analyses using a u-channel cryogenic magnetometer (natural, anhysteretic and isothermal remanent magnetizations: NRM, ARM and IRM) and a vibrating sample magnetometer indicate that a strong and stable single component characteristic remanent magnetization carried by low coercivity pseudo-single domain (PSD) grains such as magnetite can be isolated in the postglacial unit of both cores, where the inclination values vary around the geocentric axial dipole (GAD) for the latitude of the coring sites and where the maximum angular deviation (MAD) values are generally lower than 5°. Apart from one interval in each core, all the derived relative paleointensity proxies (NRM/kLF, NRM/ARM and NRM/IRM) yield similar results. NRM/IRM was used as the preferred proxy because, based on cross-spectral analysis, it is not coherent with its normalizer. Based on the comparison with paleomagnetic records from Western North America, the paleomagnetic and physical analyses indicate that both sedimentary sequences have recorded some of the first reliable Arctic high-resolution records of paleomagnetic secular variation (inclination and declination) and relative paleointensity during the Holocene. In addition, full vector paleomagnetic correlations (inclination, declination and relative paleointensity) were used to constrain the chronology of core 6JPC, using core 8JPC and other previously published and independently dated sedimentary and volcanic records from Western North America. The Accelerator Mass Spectroscopy (AMS) radiocarbon-based postglacial chronology of core 8JPC indicates sedimentation rates higher than 300 cm/kyr on the continental shelf near Barrow Canyon from approximately 8000 to 5000 cal BP, followed by a major decrease in sediment deposition. In contrast, the postglacial deposition on the slope at core site 6JPC is relatively constant and sedimentation rates are nearly three times lower.
description: The dataset consists of paleomagnetic and rock magnetic parameters 
from Holocene sediment cores from the western Alaska margin. 
The paleomagnetic data are used as one component of a Holocene 
age model for the Chukchi Sea. The rock magnetic parameters are 
sensitive to sea ice cover, paleoproductivity, and post depositional 
diagenesis in the Chukchi-Alaska margin. The parameters include 
natural remanent magnetization (NRM), geomagnetic inclination 
and declination determined from principal component analysis, 
anhysteretic remanent magnetization (ARM), isothermal remanent 
magnetization, magnetic susceptibility, wet bulk density, S-ratio, 
median destruction field of the natural remanent magnetization 
(MDF-NRM), and ratios constructed from these parameters. 
Magnetic susceptibility and bulk density were measured on a 
Geotek multisensor track. NRM, ARM, IRM, and SIRM were measured 
on a 2G model 755 cyrogenic magnetometer at the Institut des 
Sciences de la Mer (ISMER) at the Université du Québec at 
Rimouski, Canada. 

Cores HLY05-01 JPC6 and HLY05-01 JPC8 were collected during 
cruise 05-01 of the U.S. Coast Guard Cutter Healy (Healy-Oden 
Trans-Arctic Expedition "HOTRAX" Leg 1). 

Correlation of physical properties datasets between the 
jumbo piston core (JPC6) and its companion trigger core (TC) 
was used to determine the amount of section lost at the top 
of the piston core. Lisé-Pronovst et al., 2009 favor a 80cm 
adjustment of the JPC depth scale. Ortiz et al., 2009 favor 
a 147cm adjustment. Both adjustments and resulting age models 
are presented here. 

Correlation of physical properties datasets between the 
jumbo piston core (JPC8) and its companion trigger core (TC) 
was used to determine the amount of section lost at the top 
of the piston core. The depth adjustment is 51 cm.