A 200 Kyr Pleistocene lacustrine record from the Valles Caldera insight: from environmental magnetism and paleomagnetism

A BSTRACT — An ~80 m section of lacustrine sediment cored from the Valles Caldera (VC-3) was deposited over three glacial and two interglacial periods in the mid-Pleistocene. An Ar/Ar age determination of 552 + 3 ka for an ash layer at 76 m depth and major transitions recorded by multiple proxies outside this study have been combined to suggest that core VC-3 was deposited during marine isotope stages (MIS) 14 to MIS 10, including glacial terminations VI (533 ka) and V (424 ka). Alternating field demagnetization response resolves positive inclination magnetizations from samples through most of the core, consistent with Brunhes normal polarity. Three short intervals of shallow to negative inclination magnetizations may partially record geomagnetic polarity events at ~406 ka (11 α ), ~536 ka (14 α ) and the Big Lost excursion (~580 + 8 ka). Remanent magnetization in these sediments is principally carried by a range of multidomain to pseudo-single domain ferrimagnetic particles. Sedimentary deposits of glacial period 5 are typified by higher remanent magnetization and susceptibility values and interglacial times are characterized by lower intensity values. Anomalously high magnetic susceptibility and/or rock magnetic intensities measured from 48 m to 43 m are most likely due to the formation of new magnetic phases (i.e., greigite) over a lithologically distinct interval with preserved shallow mud cracks.

[1]  M. Raymo,et al.  A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records , 2005 .

[2]  C. Laj,et al.  Ar/Ar ages from transitionally magnetized lavas on La Palma, Canary Islands, and the geomagnetic instability timescale , 2002 .

[3]  Cor G. Langereis,et al.  Magnetostratigraphy and astronomical calibration of the last 1.1 Myr from an eastern Mediterranean piston core and dating of short events in the Brunhes , 1997 .

[4]  A. Roberts.  Magnetic properties of sedimentary greigite (Fe3S4) , 1995 .

[5]  A. Roberts,et al.  Environmental magnetism: Past, present, and future , 1995 .

[6]  Robert F. Butler,et al.  Paleomagnetism: Magnetic Domains to Geologic Terranes , 1991 .

[7]  M. Lanphere,et al.  Evidence for a new geomagnetic reversal from Lava flows in Idaho: Discussion of short polarity reversals in the Brunhes and late Matuyama polarity chrons , 1988 .

[8]  J. King,et al.  A comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials: Some results from lake sediments , 1982 .

[9]  K. Verosub.  Depositional and postdepositional processes in the magnetization of sediments , 1977 .

[10]  H. Johnson,et al.  Stability of Anhysteretic Remanent Magnetization in Fine and Coarse Magnetite and Maghemite Particles , 1975 .

[11]  R. Bhathal.  Magnetic anisotropy in rocks , 1971 .

[12]  D. Collinson.  Depositional remanent magnetization in sediments , 1965 .

[13]  E. Irving.  POST‐DEPOSITIONAL DETRITAL REMANENT MAGNETIZATION IN A SYNTHETIC SEDIMENT , 1964 .

[14]  C. Allen,et al.  Two middle Pleistocene glacial-interglacial cycles from the Valle Grande, Jemez Mountains, northern New Mexico , 2007, Geology of the Jemez Region II.

[15]  G. Acton,et al.  BRUNHES CHRON MAGNETIC FIELD EXCURSIONS RECOVERED FROM LEG 172 SEDIMENTS 1 , 2001 .

[16]  G. Acton,et al.  10. BRUNHES CHRON MAGNETIC FIELD EXCURSIONS RECOVERED FROM LEG 172 SEDIMENTS , 2001 .

[17]  M. Fuller,et al.  Hysteresis properties of titanomagnetites: Grain-size and compositional dependence , 1977 .

[18]  F. D. Stacey.  On the role of Brownian motion in the control of detrital remanent magnetization of sediments , 1972 .