J. E. T. Channell

University of Florida | UF · Department of Geological Sciences

The African affinity of the deformed Mesozoic continental margins surrounding the Adriatic Sea (a region known as Adria) was recognized in the 1920s. However, over the last several decades, the majority view of Mediterranean Mesozoic paleogeography has featured an ocean (Mesogea) that separated Adria and Africa in Mesozoic and early Cenozoic time....

Lack of foraminiferal carbonate in marine sediments deposited at high latitudes results in traditional oxygen isotope stratigraphy not playing a central role in Quaternary age control for a large portion of the globe. This limitation has affected the interpretation of Quaternary sediment drifts off the Antarctic Peninsula in a region critical for d...

We report magnetic properties and relative paleointensity (RPI) proxies from a suite of 10 conventional piston cores and Kasten cores from the SW Iberian Margin collected during cruise JC089 of the RSS James Cook in August 2013. Mean sedimentation rates are in the 10–20 cm/kyr range. Age models were acquired by correlation of Ca/Ti and Zr/Sr XRF co...

High-resolution sedimentary records on two cores from the Gulf of Alaska margin allow development of a ∼17,400-yr reconstruction of paleomagnetic secular variation (PSV). General agreement between the two records on their independent chronologies confirms that local PSV is recorded, demonstrating that such archives, notwithstanding complexities due...

Accurate age control of the late Tortonian to early Messinian (8.3–6.0 Ma) is essential to ascertain the origin of benthic foraminiferal δ18O trends and the late Miocene carbon isotope shift (LMCIS), and to examine temporal relationships between the deep-sea, terrasphere and cryosphere. The current Tortonian–Messinian Geological Time Scale (GTS2012...

Integrated Ocean Drilling Program (IODP) Expedition 303 to the North Atlantic provided 16 records of the Matuyama–Brunhes polarity transition (MBT), based on u-channel and discrete samples, from holes drilled at three sites (Sites U1304, U1305 and U1306) that have mean Brunhes sedimentation rates of 16–18 cm/kyr. The MBT occurs during the transitio...

Age models for new records of the Laschamp and Iceland Basin excursions from the eastern flank of the South Atlantic mid-ocean ridge (44.15 S, 14.22 W) are derived from radiocarbon dates, and from matching sea-surface temperature records to Antarctic (EPICA) air-temperature records from ice cores. The onset of the Laschamp excursion occurred during...

Integrated Ocean Drilling Program (IODP) Site U1302/3 (Orphan Knoll, off Newfoundland) recorded magnetic excursions in marine isotope stages (MIS) 9a (at 286 ka) and 13a (at 495 ka). Sites U1306 and U1305 (Eirik Drift, off SE Greenland) record excursions in MIS 14a/b (at 540 ka) and 15b/c (at 590 ka). In the excursion intervals, magnetic measuremen...

The sedimentary record of late Matuyama magnetic excursions, between the end of the Olduvai Subchron and the Matuyama-Brunhes boundary, has relied on North Atlantic Ocean Drilling Program (ODP) Sites 983/984, and individual recordings at ODP Site 1021 from the California Margin, and Core MD972143 from the west Philippine Sea. North Atlantic IODP Si...

We present a 3.2 Myr record of stable isotopes and physical properties at IODP Site U1308 (reoccupation of DSDP Site 609) located within the ice-rafted detritus (IRD) belt of the North Atlantic. We compare the isotope and lithological proxies at Site U1308 with other North Atlantic records (e.g., sites 982, 607/U1313, and U1304) to reconstruct the...

The Miocene Climatic Optimum (MCO; ~16.9 to 14.7 Ma) provides an outstanding opportunity to investigate climate-carbon cycle dynamics during a geologically recent interval of global warmth. We present benthic stable oxygen (δ18O) and carbon (δ13C) isotope records (5-12 kyr time resolution) spanning the late early to middle Miocene interval (18 to 1...

The sediment sequence from Integrated Ocean Drilling Program (IODP) Site U1304 (53°03.40′N, 33°31.78′W; water depth, 3024 m) on the southern Gardar Drift, North Atlantic Ocean, covers the last ∼1.8 Myr with a mean sedimentation rate of ∼15 cm/kyr. At Site U1304, paleomagnetic directional and relative paleointensity (RPI) records have been generated...

Core MD04-2822 from the Rockall Trough has apparent sedimentation rates of ∼ 1 m/kyr during the last deglaciation (Termination I). Component magnetization directions indicate a magnetic excursion at 16.3 m depth in the core, corresponding to an age of 26.5 ka, implying an excursion duration of ∼350 years. Across Termination I, the mean grain size o...

We present a 3.2-Myr record of stable isotopes and physical properties at IODP Site U1308 (re-occupation of DSDP Site 609) located within the ice-rafted detritus (IRD) belt of the North Atlantic. We compare the isotope and lithological proxies at Site U1308 with other North Atlantic records (e.g., Sites 982, 607/U1313 and U1304) to reconstruct the...

Integrated Ocean Drilling Program (IODP) Site U1308 (49°53'N, 24°14'W; water depth 3871 m) provides a record of relative paleointensity (RPI) and benthic stable isotope stratigraphy back to 3.2 Ma. The record since 1.5 Ma was published previously, and here we present the interval from 1.5 Ma to 3.2 Ma (Early Pleistocene-Late Pliocene). The benthic...

The Miocene Climatic Optimum (MCO; ~16.9 to 14.7 Ma) provides an outstanding opportunity to investigate climate-carbon cycle dynamics during a geologically recent interval of global warmth. We present benthic stable oxygen (d18O) and carbon (d13C) isotope records (5-12 kyr time resolution) spanning the late early to middle Miocene interval (18 to 1...

Integrated Ocean Drilling Program (IODP) Expedition 303 to the North Atlantic in 2004 recovered a 175-m Quaternary sedimentary section at IODP Site U1307, located on the northern part of the Eirik Drift, south of Greenland. The seafloor at Site U1307, at 2575 m water depth, is situated within the water-depth range of the present-day main axis of th...

We describe a quantitative magnetic unmixing method based on principal component analysis (PCA) of first-order reversal curve (FORC) diagrams. For PCA we resample FORC distributions on grids that capture diagnostic signatures of single-domain (SD), pseudo-single-domain (PSD), and multidomain (MD) magnetite, as well as of minerals such as hematite....

Paleoceanographic objectives launched three Integrated Ocean Drilling Program Expeditions to the North Atlantic during the 2003-2013 decade. Expedition 303/306 (2004/2005) was designed to recover archives of Quaternary climate from relatively high-deposition-rate sediments within the North Atlantic ice-rafted debris (IRD) belt and from regions outs...

The Iceland Basin geomagnetic excursion coincided with the marine isotope stage (MIS) 6/7 boundary. The age and duration of the excursion, at seven North Atlantic sites with sufficient isotope data, are estimated by matching marine isotope stage (MIS) 7a-c to a calibrated template. Two criteria for defining the excursion, virtual geomagnetic pole (...

In the framework of the PALEOVAN project, a high-resolution paleomagnetic and rock magnetic study was carried out on a 149 m sedimentary sequence recovered from Ahlat Ridge in the deepest part of the Lake Van (Eastern Turkey; ICDP Site 5034-2). High sedimentation rates (average ∼30 cm/ka) allow high-resolution measurements of natural remanent magne...

A composite North Atlantic record from DSDP Site 609 and IODP Site U1308 spans the past 300,000 years and shows that variability within the penultimate glaciation differed substantially from that of the surrounding two glaciations. Hematite-stained grains exhibit similar repetitive down-core variations within the Marine Isotope Stage (MIS) 8 and 4–...

As the southern extension of the Atlantic Ocean, the Weddell Sea is a key area to study Earth’s past climate variability. It constitutes a major source of Antarctic Bottom Water formation, which influences the Atlantic Meridional Overturning Circulation. Moreover, the Weddell Gyre is an important cyclonic circulation system for water-mass communica...

A new record of the Mono Lake excursion (MLE) is reported from the Summer Lake basin of Oregon, USA. Sediment magnetic properties indicate magnetite as the magnetization carrier and imply suitability of the sediments as accurate recorders of the magnetic field including relative paleointensity (RPI) variations. The magnitudes and phases of the decl...

Planktic oxygen isotope (δ18O) and relative paleointensity (RPI) data are used in tandem to generate an age model for the last 1 Myr from Integrated Ocean Drilling Program (IODP) Site U1306 drilled on the crest of the Eirik Drift (SW Greenland) in 2272 m water depth. For the 1–1.5 Ma interval, the age model is based on RPI alone due to insufficient...

Late Oligocene to Early Miocene relative paleointensity (RPI) proxies can be correlated from the equatorial Pacific (IODP Site U1334 and ODP Site 1218) to the South Atlantic (ODP Site 1090). Age models are constrained by magnetic polarity stratigraphy through correlation to a common geomagnetic polarity timescale. The RPI records do not contain sig...

We present the key features of the Valle di Manche section (Calabria, southern Italy) and discuss the pros and cons of this stratigraphic succession as a candidate section for the GSSP of the Ionian Stage (Middle Pleistocene Subseries).

A composite North Atlantic record from DSDP Site 609 and IODP Site U1308 spans the past 300,000 years and shows that variability within the penultimate glaciation differed substantially from that of the surrounding two glaciations. Hematite stained grains exhibit similar repetitive down-core variations within the Marine Isotope Stage (MIS) 8 and 4-...

Paleomagnetic analysis and radiocarbon dating of an expanded Holocene deep-sea sediment sequence recovered by Integrated Ocean Drilling Program (IODP) Expedition 303 from Labrador Sea Site U1305 (Lat.: 57°28.5 N, Long.: 48°31.8 W, water depth 3459 m) provides insights into mechanisms that drive both paleomagnetic secular variation (PSV) and magneti...

Magnetic properties of late Quaternary sediments on the SW Iberian Margin are dominated by bacterial magnetite, observed by transmission electron microscopy (TEM), with contributions from detrital titanomagnetite and hematite. Reactive hematite, together with low organic matter concentrations and the lack of sulfate reduction, lead to dissimilatory...

We present results of a multi-proxy study on marine sediment core JR179-PC466 recovered from the crest of a sediment drift offthe West Antarctic Peninsula at approximately 2300 m water depth. The 10.45 m-long core consists dominantly of glaciomarine terrigenous sediments, with only traces of calcium carbonate (1 wt%). Despite the very low abundance...

We present palaeomagnetic results from the Oligocene through Miocene part of the Integrated Ocean Drilling Program Site U1333 (1030.996'N, 138825.159'W), which is located in 4853 m-deep water over seafloor with an estimated crustal age of 46 Ma. Detailed magnetostratigraphic investigations are essential to provide a sound age model for the study of...

We present a high-resolution magnetostratigraphy and relative paleointensity (RPI) record derived from the upper 85 m of IODP Site U1336, an Equatorial Pacific early to middle Miocene succession recovered during Expedition 320/321. The magnetostratigraphy is well resolved with reversals typically located to within a few centimeters resulting in a w...

Magnetic parameters are useful for distinguishing North Atlantic Heinrich-like detrital layers from background sediments. Here we compare magnetic properties with XRF scanning data back to 700 ka and 1.3 Ma at IODP Sites U1302–U1303 and U1308, respectively. Multi-domain magnetite, with grain sizes >20 µm, is characteristic of both Ca- and Si-rich d...

High sediment accumulation rates in lacustrine and shallow-marine archives around Iceland offer the potential to compare high-resolution paleoclimatic reconstructions from terrestrial and marine archives; however, direct comparisons are hampered by difficulties in stratigraphic correlation and in deriving accurate age models for lacustrine archives...

Here we report 420 kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from th...

[1] Sediments from the equatorial Pacific Ocean, at the Integrated Ocean Drilling Program sites U1334 and U1335, record reliable magnetic polarity stratigraphies back to ~26.5 Ma (late Oligocene) at sedimentation rates usually in the 5–20 m/Myr range. Putative polarity subchrons that do not appear in current polarity timescales occur within Chrons...

Inclination patterns of natural remanent magnetization (NRM) in Quaternary sediment cores from the Arctic Ocean have been widely used for stratigraphic correlation and the construction of age models, however, shallow and negative NRM inclinations in sediments deposited during the Brunhes Chron in the Arctic Ocean appear to have a partly diagenetic...

The Arctic oceans have been fertile ground for the recording of apparent excursions of the geomagnetic field, implying that the high latitude field had unusual characteristics at least over the last 1-2 Myrs. Alternating field demagnetization of the natural remanent magnetization (NRM) of Core HLY0503-6JPC from the Mendeleev Ridge (Arctic Ocean) im...

Arctic deep-sea sediments often record intervals of negative inclination of natural remanence that are tens of centimeters thick, implying magnetic excursions with durations of tens of thousand years that far exceed excursion durations estimated elsewhere, and the lack of tight age control usually provides excessive freedom in the labeling of Arcti...

We report relative paleointensity proxy records from four piston cores collected near the Agulhas Ridge and Meteor Rise (South Atlantic). The mean sedimentation rate of the cores varies from 24 cm/kyr to 11 cm/kyr. The two cores with mean sedimentation rates over 20 cm/kyr record positive remanence inclinations at 40-41 ka coeval with the Laschamp...

We report geomagnetic directional paleosecular variation, relative paleointensity proxies and oxygen isotope data from the upper 88 m composite depth (mcd) at South Atlantic Ocean Drilling Program (ODP) Site 1089 (40°56.2?S, 9°53.64?E, 4620 m water depth). The age model is provided by high-resolution oxygen isotope stratigraphy, augmented by radioc...

A detailed record of variations in the direction and intensity of the geomagnetic field over the past 1.2 Myrs has been obtained from an ~120-m-thick sedimentary section cored at ODP Site 980 on the Feni Drift (North Atlantic). The record has high resolution due to high mean sedimentation rates (11.3 cm/kyr for the Brunhes Chron and 5.5 cm/kyr for...

We report natural remanent magnetization (NRM) directions and geomagnetic paleointensity proxies for part of the Matuyama Chron (0.9-2.2 Ma interval) from two sites located on sediment drifts in the Iceland Basin. At Ocean Drilling Program Sites 983 and 984, mean sedimentation rates in the late Matuyama Chron are 15.9 and 11.5 cm/kyr, respectively....

Here we report 420 kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from th...

Magnetic properties of late Quaternary sediments on the SW Iberian Margin are dominated by bacterial magnetite, observed by transmission electron microscopy (TEM), with contributions from detrital titanomagnetite and hematite. Reactive hematite from eolian dust, together with low organic matter concentrations and the lack of sulfate reduction, lead...

Episodes of ice-sheet disintegration and meltwater release over glacial–interglacial cycles are recorded by discrete layers of detrital sediment in the Labrador Sea1, 2. The most prominent layers reflect the release of iceberg armadas associated with cold Heinrich events3, but the detrital sediment carried by glacial outburst floods from the meltin...

Integrated Ocean Drilling Program (IODP) Expedition 303 to the North Atlantic in 2004 recovered rapidly deposited deep-sea sediments at IODP Site U1305 on Eirik Drift, located south of Greenland at 3460 m water depth, along the path of the Western Boundary Under Current (WBUC). About 200 m of sediment was sampled with u-channels from the composite...

Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflect...

Geomagnetic polarity time scales (GPTSs) have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates. A strategy to obtain an optimal GPTS is to minimize spreading rate fluctuations in many ridge systems; however, this has been possible only for a few spreading centers. We describe here...

Sedimentary relative paleointensity (RPI) data are often believed to represent a global signal at >103 yr timescales. The development of chronologies independent of oxygen isotope data (and orbital tuning) has important implications in paleoclimate science. Age models derived from RPI data could ultimately be used to better understand the climate s...

Geomagnetic excursions, defined here as brief directional aberrations of the main dipole field outside the range of expected secular variation, remain controversial. Poorly-correlated records of apparent excursions from lavas and sediments can often be assigned to sampling artifacts, sedimentological phenomena, volcanic terrane effects, or local se...

Integrated Ocean Drilling Program (IODP) Sites U1302–U1303, drilled on the SE flank of Orphan Knoll (Labrador Sea), preserve a record of detrital layers and other proxies of hydrographic change that extend the record of ice-sheet/ocean interactions through most of the Brunhes Chron. The age model is built by tandem matching of relative paleointensi...

No glacial inception is projected to occur at the current atmospheric CO 2 concentrations of 390 ppmv (ref.). Indeed, model experiments suggest that in the current orbital configuration-which is characterized by a weak minimum in summer insolation-glacial inception would require CO 2 concentrations below preindustrial levels of 280 ppmv (refs 2-4)....

No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv (ref. ). Indeed, model experiments suggest that in the current orbital configuration--which is characterized by a weak minimum in summer insolation--glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv (refs , ,...

Episodes of ice-sheet disintegration and meltwater release over glacial-interglacial cycles are recorded by discrete layers of detrital sediment in the Labrador Sea. The most prominent layers reflect the release of iceberg armadas associated with cold Heinrich events, but the detrital sediment carried by glacial outburst floods from the melting Lau...

Integrated Ocean Drilling Program (IODP) Sites U1302-U1303, drilled on the SE flank of Orphan Knoll (Labrador Sea), preserve a record of detrital layers and other proxies of hydrographic change that extend the record of ice-sheet/ocean interactions through most of the Brunhes Chron. The age model is built by tandem matching of relative paleointensi...

Integrated Ocean Drilling Program (IODP) Expedition 303 to the North Atlantic in 2004 recovered rapidly deposited deep-sea sediments at IODP Site U1305 on Eirik Drift, located south of Greenland at 3460 m water depth, along the path of the Western Boundary Under Current (WBUC). About 200 m of sediment was sampled with u-channels from the composite...

Site U1338 was drilled in the Equatorial Pacific Ocean during IODP Expedition 321. Sediment at the site consists of nannofossil oozes and chalks with varying amounts of diatoms and radiolarians. Of the almost 450 m-thick composite section only three intervals produced a clear magnetic stratigraphy from shipboard data measured on half-cores. The 0-6...

Integrated Ocean Drilling Program (IODP) Expeditions 320 and 321 recovered sediment cores from equatorial Pacific. Cores were taken at eight Sites (U1331-U1338) and onboard measurements showed that those from Sites U1331, U1332, U1333 and U1334 covered Eocene and/or Oligocene (Expedition 320/321 Scientists, 2010). Although many efforts have been ma...

An age model for the Brunhes Chron for Ocean Drilling Program (ODP) Site 1063 (Bermuda Rise) is based on the tandem correlation of oxygen isotope and relative paleointensity data to calibrated reference templates. Four intervals in the Brunhes Chron where component inclinations are negative, for both u-channel samples and discrete samples, are corr...

Since the 1960s, possible correlation between geomagnetic field strength and polarity length on 10^6 years or longer time scale has been suggested, and its relation to geodynamo processes has been discussed (e.g., Cox, 1968). Paleointensity estimation using single crystal silicate indicated that the geomagnetic field was stronger during Cretaceous...

A better understanding of millennial and eventually even centennial scale variations of the geomagnetic field are required if we are to decipher the causes and consequences of geomagnetic change. Records of paleomagnetic secular variation (PSV) in the eastern North Pacific region are few, resulting in poorly constrained variability and contrasting...

IODP Site U1302-U1303, on the SE flank of Orphan Knoll (Labrador Sea), has a record of detrital layers that extends through most of the Brunhes Chron. The age model is built by tandem matching of relative paleointensity (RPI) and oxygen isotope data (δ18O) from Neogloboquadrina pachyderma (sin.) to reference records, indicating a mean Brunhes sedim...

We identified a distinct red, detrital-carbonate layer deposited during early MIS 5e in cores from the Labrador Sea. Sediment records from Orphan Knoll (IODP site U1302/3: 50o 10' N, 45o 38' W) and Eirik Drift (IODP site U1305: 57o 29' N, 48o 32' W) both contain obvious red layers (~30 and ~10 cm thick respectively) marked by high values of the a*...

Biostratigraphy based on calcareous nannofossils, integrated by magnetostratigraphic, geochronological and isotopic data, allowed establishing a precise chronological framework for the Pleistocene succession within the south-western sector of the Crotone Basin (Calabria, Southern Italy), where the Pliocene–Pleistocene global stratotype section and...

A high-resolution rock magnetic study of a Late Pleistocene core from the Labrador Sea, north of the Eirik Ridge on the Greenland rise, reveals three main features in the downcore variation of the rock magnetic parameters. Two are at the glacial–interglacial transitions (i.e., isotope stages 6–5e and 2–1), showing magnetic grain-size coarsening and...

We report stable isotope, core scanning XRF, and ice-rafted detritus (IRD) data in glacial-aged sediments from piston Core KN166-14-JPC-13 (hereafter referred to as JPC-13) retrieved at 53.1°N 33.5°W on the southern Gardar Drift, North Atlantic. A chronology was established by correlating millennial-scale features in the benthic δ18O record to Port...

When five Matuyama-Brunhes (M-B) boundary records from the North Atlantic are placed on isotope age models, produced by correlation of the δ18O record directly or indirectly to an ice volume model, the M-B boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773.1 ka (standard de...

Sediment samples recovered during Integrated Ocean Drilling Program Expeditions 320 and 321 of the Pacific Equatorial Age Transect (PEAT) program retrieved well preserved continuous core material from the equatorial eastern Pacific providing an excellent archive for the study of paleoclimatic, paleoceanographic, paleoproductivity, and other paleoen...

Alternating field demagnetization of natural remanent magnetization (NRM) of sediment cores from the Lomonosov Ridge and Yermak Plateau yields intervals of shallow and negative inclination in Brunhes-aged sediments. Thermal demagnetization of the NRM indicates that shallow and negative inclination components in the two cores are often largely ``unb...

The geological perspective for a current decline of Arctic sea ice and its consequences can be derived from sedimentary proxy records from the Arctic Ocean floor, but their interpretation is complicated by commonly poor preservation of biogenic material and age uncertainties. New sediment-core data from the western Arctic Ocean show a pronounced ch...

In recent years global geomagnetic models have made substantial progress in recreating the paleo field. However, the accuracy of these efforts is poorly constrained in the Pacific sector, where geomagnetic secular variation is thought to be subdued. Here we present high-resolution paleomagnetic secular variation (PSV) records from the Gulf of Alask...

A recently recovered ∼6-m long Holocene sedimentary sequence (piston Core 2004-804-650) collected from the Beaufort Sea (western Canadian Arctic) was dated by combining the paleomagnetic secular variation (PSV) and a time-varying spherical harmonic model of the geomagnetic field (CALS7k.2). A u-channel-based paleomagnetic study reveals the presence...

Existing correlations of Early Cretaceous nannofossil events to polarity zones in Italian pelagic limestones are the basis for correlation of polarity chrons to geologic stages, and hence calibration of the Early Cretaceous geomagnetic polarity timescale. Here, we present correlations of nannofossil events to polarity chrons for the Late Jurassic a...

The sites occupied during Integrated Ocean Drilling Program Expedition 303/306 were chosen to recover late Miocene to Quaternary records of North Atlantic environmental variability at elevated mean sedimentation rates from locations appropriate for oxygen isotope (δ 18 O) and relative paleointensity (RPI) stratigraphies. The overall objective is to...

Long-time records of biogenic silica (opal) help researchers to evaluate the effects of global climatic, tectonic, and geochemical Cenozoic events on biological paleoproductivity. Integrated Ocean Drilling Program Expedition 321 Site U1337 contains expanded , nearly continuous records of diatomaceous sediment deposited in deep waters of the eastern...