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Adam Maloof - Publications

Chronological —Topical


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Research Topics and Fundamental Questions

The Geometry of Earth's Magnetic Field

Central to all paleomagnetic studies is the Geocentric Axial Dipole Hypothesis, which states that, throughout Earth history, when averaged over 10,000 years or more, Earth's magnetic field can be closely approximated by a dipole magnet aligned with the spin axis (i.e., geographic north). However, today there is a persistent 4% quadrupolar component to the field, and in the past, larger nondipole fields may have a affected our paleomagnetic records of paleogeography and the supercontinent cycle. 1.1 billion year old lavas from a failed rift in Ontario, Canada were considered the strongest case for ancient non-dipole fields. We revisited this location and showed that the supposed asymmetric magnetic reversals were an artifact of nonstratigraphic sampling and rapid equatorward motion of the North American continent. We also studied in detail the magnetic mineralogy of variably oxidized basalt flows in order to understand how coexisting magnetite and hematite phases record Earth's ancient magnetic field.

Equal-area projection of magnetic directions from 1.1 billion year old basalts at Mamainse Point, Ontario.

29. Swanson-Hysell, N.L, Feinberg, J.M., Berquó and Maloof, A.C. 2011, Self-reversed magnetization held by martite in basalt ows from the 1.1-billion-year-old Keweenawan rift, Canada, Earth and Planetary Science Letters, 305 pp. 171-184.  [pdf]

15. Swanson-Hysell, N.L., Maloof, A.C., Weiss, B.P. and Evans, D.A.D. 2009, No asymmetry in geomagnetic reversals recorded by 1.1-billion-year-old Keweenawan basalts, Nature Geoscience, 2 pp. 713-717. DOI: 10.1038/NGEO622. [pdf]

Figure caption: Equal-area projection of magnetic directions from 1.1 billion year old basalts at Mamainse Point, Ontario.  Note the motion of upper-hemisphere 'reveresed' directions (colors) toward a lesser degree of reversal asymmetry (shallower inclination) with decreasing age.


True Polar Wander

True polar wander (TPW) refers the motion of the solid Earth with respect to the spin axis, which remains fixed in the solar system, at rates as much as ten times faster than plate tectonics. TPW occurs today in response to the redistribution of ice and water loads, however its importance in the past remains uncertain. We have documented a pair of TPW events and consequent local sea level and climate perturbations and global carbon isotope shifts from age-equivalent rocks in both the Norwegian Arctic (Svalbard) and Australia (~800 million years ago). This work both sets new limits for global change, and documents the ambient climate regime immediately preceding the snowball Earth glaciations of the Cryogenian Period. We have begun a new project in coeval sediments from northern Ethiopia in order to quantify rates of TPW using ID-TIMS U/Pb zircon geochronology of volcanic ashes erupted from nearby arc volcanoes and interbedded with the ~800 Ma carbonates.

36. Swanson-Hysell, N.L, Maloof, A.C., Evans, D.A.D., Kirschvink, J.L., Halverson, G.P. and Hurtgen, M.T. 2012, Constraints on Neoproterozoic paleogeography and Paleozoic orogenesis from paleomagnetic records of the Bitter Springs Formation, Amadeus Basin, central Australia, American Journal of Science. [pdf]

30.
Mitchell, R.N., Kilian, T.M., Raub, T.D., Evans, D.A.D., Bleeker, W. and Maloof, A.C. 2011, Sutton hotspot: Resolving Ediacaran-Cambrian tectonics and true polar wander for
Laurentia, American Journal of Science, 311, pp. 651–663. [pdf]

20.  Jones, D.S., Maloof, A.C., Hurtgen, M.T., Rainbird, R.H. and Schrag, D.P. 2010, Regional and global chemostratigraphic correlation of the early Neoproterozoic Shaler Supergroup, Victoria Island, Northwestern Canada Precambrian Research, 181 pp. 43-63, doi:10.1016/j.precamres.2010.05.012.  [pdf]

Stratigraphy of the Pre-Cryogenian carbonate platform.

13.  Halverson, G.P., Dudas, F.Ö., Maloof, A.C. and Bowring, S.A. 2007, Evolution of the 87Sr/86Sr composition of Neoproterozoic seawater; Palaeogeography, Palaeoclimatology, Palaeoecology, 256 pp. 103-129 doi:0.1016/j.palaeo.2007.02.028. [pdf]

11.  Halverson, G.P., Maloof, A.C., Schrag, D.P., Dudas, F.O., and Hurtgen, M.T. 2007, Stratigraphy and geochemistry of an 800 Ma negative carbon isotope stage in northeast Svalbard; Chemical Geology, 237 pp. 5-27. doi: 10.1016/j.chemgeo.2006.06.013. [pdf]

9.  Maloof, A.C., Halverson, G.P., Kirschvink, J.L., Schrag, D.P., Weiss, B.P., and Hoffman, P.F. 2006, Combined paleomagnetic, isotopic, and stratigraphic evidence for true polar wander from the Neoproterozoic Akademikerbreen Group, Svalbard; Geological Society of America Bulletin, 118 pp. 1099-1124. doi: 10.1130/B25892.1. [pdf]

Figure caption: Stratigraphy of the Pre-Cryogenian carbonate platform from northeastern Svalbard, Norway.  Across the only two pre-glacial sequence boundaries (relative sea level changes, labeled G1 and S1) we see coincident shifts in the carbon-isotopic composition of the ocean (black) and the paleomagnetic orientation of the North American continent, to which Svalbard was attached (green). Currently, we are reporting on a remarkably similar pattern in Australian rocks of the same age and using this the fingerprint of true polar wander to place new constraints on the paleogeography of the Rodinia supercontinent.


Snowball Earth Hypothesis

The snowball Earth hypothesis was developed to explain the juxtaposition of equatorial glacial sediments deposited at sea level and associated chemical sediments that may indicate long term isolation of the ocean from the atmosphere. However, a global carapace of thick sea ice may not be compatible with observations of (A) thick interbedded glacial and non-glacial deposits perhaps indicative of advancing and retreating temperate glaciers fed by a vigorous hydrological cycle, and (B) the survival of a diversity of eukaryotic lineages, including multicellular life, perhaps requiring open seas rather than just isolated refugia around cracks and volcanic islands. Our work is testing the snowball Earth hypothesis by mapping-out basin-scale 3D glacial landscapes and the physical- and chemo-stratigraphic architecture of the pre-, syn- and post-glacial record, building a new absolute geochronology for the Cryogenian Period, and reconstructing 3D models of the primitive animals that may have survived the snowball Earth.

The oldest animal fossils: In particular, we report on our discovery of 1 cm-sized body fossils from limestones that pre-date the terminal Cryogenian (~635 Ma) ice age. We interpret the fossils as the bodies of sponge-grade animals that inhabited stromatolite bioherms during the largest carbon-isotope anomaly in Earth history. This discovery represents the oldest animal-grade body fossils ever reported, and is consistent with independent lipid biomarker and molecular clock data that suggest the presence of sponges prior to the Ediacaran Period. In order to interpret the functional morphology of these fossils, we designed a streamlined technique of automated serial grinding and imaging to create 3D digital reconstructions of the fossils, despite the lack of density or solubility contrasts between the fossils and matrix. We continue to use this new technology for the digital reconstruction of early animals and algae, and are exploring other applications. In particular, we are using this technique to monitor the evolving integrity of carbonate seal rocks during CO2 sequestration experiments, where serial grinding/imaging allows us to image reaction products and porosity/permeability changes related to the interaction between injected CO2 and the carbonate seals. 

38.  Catherine V. Rose, Maloof, A.C., Blair Schoene, Ryan C.Ewing, Ulf Linnemann, Mandy Hofmann and John M. Cottle. 2013. The End-Cryogenian Glaciation of South Australia, Geoscience Canada, 40, pp. 256-293, doi: geocanj.2013.40.019. [pdf]

34.  Hoffman, P.F., Halverson, G.P., Domack, E.W., Maloof, A.C., Swanson-Hysell, N.L. 2012, Cryogenian glaciation in East Greenland and NE Svalbard revisited: Sturtian age for the Ulves-Petrovbreen diamictites, Precambrian Research, 206-207, pp. 137-158. [pdf]

31.  Rose, C.V., Husson, J.L., Swanson-Hysell, N.L., Poppick, L.N., Cottle, J.M., Schoene, B. and Maloof, A.C. 2011, Constraints on the origin and relative timing of the Trezona δ13C anomaly below the end-Cryogenian glaciation, Earth and Planetary Science Letters, 319-320, pp. 241-250. [pdf]

24.  Maloof, A.C., Rose, C.V., Beach, R., Samuels, B.M., Calmet, C.C., Erwin, D.H., Poirier, G.R., Yao, N. and Simons, F.J. 2010, Possible animal-body fossils in pre-Marinoan limestones from South Australia, Nature Geoscience, 3, pp. 653-659, doi:10.1038/ngeo934. [pdf]

23.  Rose, C.V. and Maloof, A.C. 2010, Testing models for post-glacial `cap dolostone' deposition: Nuccaleena Formation, South Australia, Earth and Planetary Science Letters, 296 pp.165-180, doi:10.1016/j.epsl.2010.03.031. [pdf]

21.  Swanson-Hysell, N.L, Rose, C.V., Calmet, C.C., Halverson, G.P., Hurtgen, M.T. and Maloof, A.C. 2010, Cryogenian Glaciation and the Onset of Carbon-Isotope Decoupling, Science, 328 pp. 608-611, doi:10.1126/science.1184508. [pdf]

19.  Macdonald, F.A., Schmitz, M.D., Crowley, J.L., Roots, C.F., Jones, D.S., Maloof, A.C., Strauss, J.V., Cohen, P.A., Johnston, D.T., Schrag, D.P. 2010, Calibrating the Cryogenian, Science, 327 pp. 1241-1243, doi:10.1126/science.1183325. [pdf]

8.  Halverson, G.P., Hoffman, P.F., Schrag, D.P., Maloof, A.C., and Rice, A.H.N. 2005, Toward a Neoproterozoic composite carbon-isotope record; Geological Society of America Bulletin, 117 pp. 1181-1207. doi:10.1130/B25630.1.  [pdf]

6. Halverson, G.P., Maloof, A.C., Hoffman, P.F. 2004, The Marinoan glaciation (Neoproterozoic) in northeast Svalbard, Basin Research 16 pp. 297-324. doi:10.1111/j.1365-2117.2004.00234.x.  [pdf]

Dropstone (~5 cm diameter) in the Ghaub Fm glacimarine diamictite (~ 635 Ma), Northern Namibia.

5. Ho ffman, P.F. and Maloof, A.C. 2003, Comment on: A complex microbiota from snowball Earth times: Microfossils from the Neoproterozoic Kingston Peak Formation, Death Valley, USA, by Corsetti, F.A., Awramik, S.M., and Pierce, D., Proceedings of the National Academy of Sciences, 100 pp. 4399-4404. [pdf]

4. 
Maloof, A.C., Kellogg, J.B., and Anders, A.M. 2002, Neoproterozoic sand wedges: crack formation in frozen soils under diurnal forcing during a snowball Earth, Earth and Planetary Science Letters, 204 pp. 1-15. doi:10.1016/S0012-821X(02)00960-3. [pdf]

3.  Hoffman, P.F. and Maloof, A.C. 2001, Tilting at Snowballs, A comment on Proterozoic equatorial glaciation: Has 'snowball Earth' a snowball's chance?, by Williams, G.E. and Schmidt, P.W., The Australian Geologist 117 pp. 21-25, 2000. [pdf]

2.  Maloof, A.C. 2000, Superposed folding at the junction of the inland and coastal belts, Damaran orogen, NW Namibia, Communications of the Geological Survey of Namibia, Henno Martin Commemorative Volume 12 pp. 89-98. [pdf]

1.  Hoffman, P.F. and Maloof, A.C. 1999, The Snowball theory still holds water; Nature 397 p. 384. doi: 10.1038/17006. [pdf]

Figure caption: Dropstone (~5 cm diameter) in the Ghaub Fm glacimarine diamictite (~ 635 Ma), Northern Namibia.  Marine sediments with ice-rafted debris are nearly ubiquitous on all continents at low paleolatitudes during early (Sturtian) and late (Marinoan) Cryogenian glaciations.


Extreme Negative Carbon-Isotope Anomalies:

After the low-latitude Cryogenian glaciations and immediately before the soft-bodied Ediacaran organisms enter the fossil record, glaciers were present on at least five diff erent cratons, local sea level may have dropped and risen again by as much as 1 km on at least four cratons, and the deepest carbon isotope excursion in Earth history was recorded in carbonate sediments on at least seven cratons. Peculiar to this `Shuram' carbon-isotope event is the observation that δ13 C of organic carbon does not covary with δ13 C of carbonate carbon, suggesting that organic carbon in marine sediments was not derived from contemporaneous dissolved inorganic carbon— a situation very di fferent from today and most of the Phanerozoic. What is the link between the anomalous carbon cycle behavior, animal evolution, sea level, and glaciation? We are starting to answer this question with integrated mapping, physical stratigraphy, and isotope work in the contemporaneous Wonoka Formation of South Australia. Our most important nd to date is geological evidence that theδ13C nadir and most of the recovery was recorded in shelf sediments prior to and contemporaneous with canyon incision—thus ruling out a burial-diagenesis model for the covarying and very negativeδ13C—δ18O record from carbonates.

35.  Husson, J.L., Maloof, A.C. and Schoene, B. 2012, A syn-depositional age for Earth’s deepest δ13C excursion required by isotope conglomerate tests, Terra Nova, 24, pp 318-325. [pdf]


The Cambrian Explosion

By 1859, Darwin had recognized the sudden appearance of animal fossils in the geologic record, after more than three billion years with just bacteria and algae, as the most signi cant challenge to his hypothesis for the origin of species. Since Darwin, scientists have recognized animal fossils much older than trilobites. Ediacaran animals resembling jelly fi sh and sea pens appear at least 575 million years ago, and lipid biomarker and molecular phylogenetic studies indicate an even more ancient record back to 635 Ma for some animals like sponges. Despite these discoveries, the spectacular radiation of animals recognizable as ancestors of organisms today still seems to have occurred suddenly and during an interval of profound volatility in the global carbon cycle known as the Cambrian explosion (542-515 million years ago). In these papers, we integrate six years of field work and a large new physical and chemostratigraphic dataset from Morocco with published data from Siberia, Mongolia and China to construct the first, U-Pb zircon age-constrained, biostratigraphy-independent, global record of geochemical and paleobiological change during the Early Cambrian. The new time line will form the backbone for future work on the coevolution of animals and ocean geochemistry and for the International Subcommission on Cambrian Stratigraphy. Through improved correlation and radiometric dating, our work resolves the problem of explosive diversication of animals at the start of the Tommotian, and shows that this diversication was drawn out over more than 20 million years. Additionally, we confi rm that the switch between aragonite seas and calcite seas controls the de novo acquisition of carbonate animal skeletons and show, with a simple box-model, how this switch is a result of long-term rise in sea level, declining in 87Sr/86Sr, and increasing oxidation state of the shallow marine sediment-water interface.

 

xx. Maloof, A.C. 2011, The earliest Cambrian record of animals and ocean geochemical change, American Scientist, in prep.

27.  Maloof, A.C., Porter, S.M., Moore, J.L., Dudás, F.Ö., Bowring, S.A., Higgins, J.A., Fike, D.A. and Eddy, M.P. 2010, The earliest Cambrian record of animals and ocean geochemical change, Geological Society of America Bulletin, 122, pp. 1731-7774. [pdf]

22.  Maloof, A.C., Ramezani, J., Bowring, S.A., Fike, D.A., Porter, S.M. and Mazouad, M. 2010, Constraints on early Cambrian carbon cycling from the duration of the Nemakit-DaldynianTommotian boundary δ13C shift, Morocco, Geology, 38 pp. 623-626, doi: 10.1130/G30726.1. [pdf]

7.  Maloof, A.C., Schrag, D.P., Crowley, J.L., and Bowring, S.A. 2005, An expanded record of Early Cambrian carbon cycling from the Anti-Atlas Margin, Morocco; Canadian Journal of Earth Sciences, 42 pp. 2195-2216. doi: 10.1139/E05-062.  [pdf]

Figure caption: Upper part of the Adoudounian Formation, Early Cambrian, Anti Atlas Mountains, Morocco.


Cenozoic Analogs

Virtually all pre-Mesozoic records of Earth history and climate change are derived from shallow water carbonates deposited on continental shelves. However, we know surprisingly little about how modern analog sedimentary environments record global change. By pairing cm-resolution digital surface mapping with hundreds of sediment cores, we showed how the vertical and lateral distribution of carbonate facies record the well-constrained history of Holocene sea level. We can now use this quantitative framework to interpret the amplitude and time scale of sea level variability inferred from the stratal architecture preserved in ancient carbonates. As part of this project, we also have documented how records of the geomagnetic field and carbon and oxygen isotopes are acquired and preserved in shallow water carbonates. At the same time, we have refi ned the methodology for deciphering periodic forcing in rhythmically-laminated sediment, and written open-source software for plotting and analyzing stratigraphic data.

33.  Proistosescu, C., Maloof, A.C. and Huybers, P. 2011, To tune or not to tune? - Detecting orbital variability in pre-Pleistocene climate records, Earth and Planetary Science Letters, 325-326 pp. 100-107. [pdf]

False color Ikonos satellite image of meandering tidal channels.

32. Maloof, A.C. and Grotzinger, J.P. 2012, The Holocene shallowing-upward parasequence of north-west Andros Island, Bahamas, Sedimentology, 59, 1375-1407, doi: 10.1111/j.1365-3091.2011.01313.x. [pdf]

28. Lewis, K.W., Keeler, T.L., Maloof, A.C. 2011, MatStrat: New software for plotting and analyzing stratigraphic data, EOS Transactions of the American Geophysical Union, 92, pp. 37-38. [pdf]

16. Kopp, R. E., Schumann, D., Raub, T.D., Powars, D.S., Godfrey, L.V., 2Swanson-Hysell, N.L., Maloof, A.C. and Vali, H. 2009, An Appalachian Amazon? Magnetofossil evidence for the development of a tropical river-like system in the mid-Atlantic United States during the Paleocene-Eocene thermal maximum, Paleoceanography, 24, PA4211, doi:10.1029/2009PA001783. [pdf]

12.  Maloof, A.C., Kopp, R.E., Grotzinger, J.P., Fike, D.A., Bosak, T., Vali, H., Poussart, P.M., Weiss, B.P. and Kirschvink, J.L. 2007, Sedimentary iron cycling and the origin and preservation of magnetization in platform carbonate muds, Andros Island, Bahamas; Earth and Planetary Science Letters, 259 pp.581-598. DOI: 10.1016/j.epsl.2007.05.021.  [pdf]

10.  Kopp, R.E., Weiss, B.P., Maloof, A.C., Vali, H., Nash, C.Z., and Kirschvink, J.L. 2006, Chains, clumps, and strings: Magnetofossil taphonomy with ferromagnetic resonance spectroscopy; Earth and Planetary Science Letters, 247 pp. 10-25. doi:10.1016/j.epsl.2006.05.001.  [pdf]

Figure caption top: The untuned (black) and tuned (red) d18O spectral power (y-axis) versus period in millions of years (x-axis). We show 99% confidence intervals determined from red noise (tuorquoise) and tuned red noise (green).

Figure caption bottom: False color Ikonos satellite image of meandering tidal channels in carbonate muds of the northwestern Edge of Andros Island, Bahamas.


Sea Level during the Last Interglacial Period:

Though its warmth (polar temperatures ~3- 5°C warmer than today) was caused partly by variations in Earth's obliquity, the Last Interglacial (LIG) stage (ca. 130,000 - 115,000 years ago) serves as a partial analog for low-end future warming scenarios. Multiple indicators suggest LIG global sea level was higher than at present; based upon a small set of local sea level indicators, the IPCC Fourth Assessment Report inferred an elevation of ~4-6 meters. However, sea level often is mistakenly viewed as a simple function of changing global ice volume. This viewpoint neglects local variability, which arises from several factors, including the distortion of the geoid and the elastic and isostatic eff ects of lithospheric deformation by shifting ice masses. Therefore, we built a new globally-extensive database of physical and chemical sea level indicators and used a probabalistic approach to demonstrate that, during the last interglacial period (~120 ka), sea level was >6 m higher than today.

37. Kopp, Robert E., Simons, Frederik J. , Mitrovica, Jerry X., Maloof, A. C. and Oppenheimer, Michael. 2013, A probabilistic assessment of sea level variations within the last interglacial stage, Geophys. J. Int., 192(3), pp. 1-6, doi: ggt029v1-ggt029. [pdf]

17.  Kopp, R.E., Simons, F.J., Mitrovica, J.X., Maloof, A.C., Oppenheimer, M. 2009, Probabilistic assessment of sea level during the Last Interglacial, Nature, 462 pp. 863-867, doi:10.1038/nature0686.  [pdf]

Figure caption: Our prediction of the sea level anomaly (compared to sea level today) during the last interglacial (~124 ka), based on geographically distributed relative sea level information from raised beaches, wave-cut terraces, coral biofacies, sedimentary environment and d18O of benthic foraminifera.


Impact Craters

Impact craters: Most of the martian and lunar surface is made of basalt. Scientists would like to use the geometry of craters and ejecta blankets and patterns of crustal magnetization on Mars and the Moon to infer properties of Martian and Lunar crust, such as rheology, ice content, and mineralogy.
 

We created the first geological map, digital elevation model, and rock magnetic survey of Lonar Crater, Earth's closest analog to small impact crater forming processes on Mars and the Moon.

26.  Weiss, B.P., Pedersen, S., Garrick-Bethell, I., Stewart, S.T., Louzada, K.L., Maloof, A.C. and Swanson-Hysell, N.L. 2010, Earth and Planetary Science Letters, 298, pp. 66-76, doi:10.1016/j.epsl.2010.07.028. [pdf]

18. Maloof, A.C., Stewart, S.T., Weiss, B.P., Soule, S.A., Swanson-Hysell, N.L., Louzada, K.L., Garrick-Bethell, I. and Poussart, P.M. 2010, Geology of Lonar Crater, Geological Society of America Bulletin, 122 pp. 109-126, doi: 10.1130/B26474.1.  [pdf]

14.  Louzada, K.L., Weiss, B.P., Maloof, A.C., Swanson-Hysell, N.L. and Soule, S.A. 2008, Paleomagnetism of Lonar Impact Crater, India, Earth and Planetary Science Letters, 275 pp. 308-319, doi:10.1016/j.epsl.2008.08.02.  [pdf]

Figure caption: Quickbird satellite image of Lonar Crater, Maharashtra India.  Image is draped over a GPS-derived digital elevation model.


The Atomic Magnetometer

In collaboration with Professor Mike Romalis (Princeton Department of Physics), we have adapted his atomic magnetometer to measure rocks. The advantages of the new system over conventional SQuID magnetometers include 1-3 orders of magnitude higher moment sensitivity, the possibility of in situ thermal demagnetization and therefore a great reduction in analysis time for a single sample, and a ten-fold reduction in instrument cost. We used a prototype instrument to successfully demonstrate that the method works and can reproduce SQuID measurements, and now I am part of an NSF-funded advisory board (led by John Tarduno, Rochester) to commercialize the instrument.

25. Dang, H.B., Maloof, A.C. and Romalis, M.V. 2010, Ultrahigh sensitivity magnetic field and magnetization measurements with an atomic magnetometer, Applied Physics Letters, 97,
151110. [pdf]