Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Michael P. Eddy is active.

Publication


Featured researches published by Michael P. Eddy.


Geological Society of America Bulletin | 2010

The earliest Cambrian record of animals and ocean geochemical change

Adam C. Maloof; Susannah M. Porter; John L. Moore; Frank Dudás; Samuel A. Bowring; J.A. Higgins; David A. Fike; Michael P. Eddy

The Cambrian diversification of animals was long thought to have begun with an explosive phase at the start of the Tommotian Age. Recent stratigraphic discoveries, however, suggest that many taxa appeared in the older Nemakit-Daldynian Age, and that the diversification was more gradual. We map lowest Cambrian (Nemakit-Daldynian through Tommotian) records of δ 13 C CaCO 3 variability from Siberia, Mongolia, and China onto a Moroccan U/Pb–δ 13 C CaCO 3 age model constrained by five U/Pb ages from interbedded volcanic ashes. The δ 13 C CaCO 3 correlations ignore fossil tie points, so we assume synchroneity in δ 13 C trends rather than synchroneity in first appearances of animal taxa. We present new δ 13 C org , 87 Sr/ 86 Sr, uranium, and vanadium data from the same carbonate samples that define the Moroccan δ 13 C CaCO 3 curve. The result is a new absolute time line for first appearances of skeletal animals and for changes in the carbon, strontium, and redox chemistry of the ocean during the Nemakit-Daldynian and Tommotian ages at the beginning of the Cambrian. The time line suggests that the diversification of skeletal animals began early in the Nemakit-Daldynian, with much of the diversity appearing by the middle of the age. Fossil first appearances occurred in three pulses, with a small pulse in the earliest Nemakit-Daldynian (ca. 540–538 Ma), a larger pulse in the mid- to late Nemakit-Daldynian (ca. 534–530 Ma), and a moderate pulse in the Tommotian (ca. 524–522 Ma). These pulses are associated with rapid reorganizations of the carbon cycle, and are superimposed on long-term increases in sea level and the hydrothermal flux of Sr.


Science | 2015

U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction

Blair Schoene; Kyle M. Samperton; Michael P. Eddy; Gerta Keller; Thierry Adatte; Samuel A. Bowring; Syed F.R. Khadri; B. Gertsch

Dating the influence of Deccan Traps eruptions The Deccan Traps flood basalts in India represent over a million cubic kilometers of erupted lava. These massive eruptions occurred around the same time as the end-Cretaceous mass extinction some 65 million years ago, which famously wiped out all nonavian dinosaurs. Schoene et al. determined the precise timing and duration of the main phase of the eruptions, which lasted over 750,000 years and occurred just 250,000 years before the Cretaceous-Paleogene boundary. The relative contribution of these eruptions and of the Chicxulub impact in Mexico to the mass extinction remains unclear, but both provide potential kill mechanisms. Science, this issue p. 182 The main phase of the Deccan Traps eruption began 250,000 years before the end-Cretaceous extinction and lasted 750,000 years. The Chicxulub asteroid impact (Mexico) and the eruption of the massive Deccan volcanic province (India) are two proposed causes of the end-Cretaceous mass extinction, which includes the demise of nonavian dinosaurs. Despite widespread acceptance of the impact hypothesis, the lack of a high-resolution eruption timeline for the Deccan basalts has prevented full assessment of their relationship to the mass extinction. Here we apply uranium-lead (U-Pb) zircon geochronology to Deccan rocks and show that the main phase of eruptions initiated ~250,000 years before the Cretaceous-Paleogene boundary and that >1.1 million cubic kilometers of basalt erupted in ~750,000 years. Our results are consistent with the hypothesis that the Deccan Traps contributed to the latest Cretaceous environmental change and biologic turnover that culminated in the marine and terrestrial mass extinctions.


Scientific Reports | 2015

Natural quasicrystal with decagonal symmetry

Luca Bindi; Nan Yao; Chaney Lin; Lincoln S. Hollister; Christopher L. Andronicos; Vadim V. Distler; Michael P. Eddy; Alexander Kostin; Valery Kryachko; Glenn J. MacPherson; William M. Steinhardt; Marina A. Yudovskaya; Paul J. Steinhardt

We report the first occurrence of a natural quasicrystal with decagonal symmetry. The quasicrystal, with composition Al71Ni24Fe5, was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite. Icosahedrite, Al63Cu24Fe13, the first natural quasicrystal to be identified, was found in the same meteorite. The new quasicrystal was found associated with steinhardtite (Al38Ni32Fe30), Fe-poor steinhardtite (Al50Ni40Fe10), Al-bearing trevorite (NiFe2O4) and Al-bearing taenite (FeNi). Laboratory studies of decagonal Al71Ni24Fe5 have shown that it is stable over a narrow range of temperatures, 1120 K to 1200 K at standard pressure, providing support for our earlier conclusion that the Khatyrka meteorite reached heterogeneous high temperatures [1100 < T(K) ≤ 1500] and then rapidly cooled after being heated during an impact-induced shock that occurred in outer space 4.5 Gya. The occurrences of metallic Al alloyed with Cu, Ni, and Fe raises new questions regarding conditions that can be achieved in the early solar nebula.


Nature Communications | 2014

Impact-induced shock and the formation of natural quasicrystals in the early solar system

Lincoln S. Hollister; Luca Bindi; Nan Yao; Gerald R. Poirier; Christopher L. Andronicos; Glenn J. MacPherson; Chaney Lin; Vadim V. Distler; Michael P. Eddy; Alexander Kostin; Valery Kryachko; William M. Steinhardt; Marina A. Yudovskaya; John M. Eiler; Yunbin Guan; Jamil J. Clarke; Paul J. Steinhardt

The discovery of a natural quasicrystal, icosahedrite (Al63Cu24Fe13), accompanied by khatyrkite (CuAl2) and cupalite (CuAl) in the CV3 carbonaceous chondrite Khatyrka has posed a mystery as to what extraterrestrial processes led to the formation and preservation of these metal alloys. Here we present a range of evidence, including the discovery of high-pressure phases never observed before in a CV3 chondrite, indicating that an impact shock generated a heterogeneous distribution of pressures and temperatures in which some portions reached at least 5 GPa and 1,200 °C. The conditions were sufficient to melt Al-Cu-bearing minerals, which then rapidly solidified into icosahedrite and other Al-Cu metal phases. The meteorite also contains heretofore unobserved phases of iron-nickel and iron sulphide with substantial amounts of Al and Cu. The presence of these phases in Khatyrka provides further proof that the Al-Cu alloys are natural products of unusual processes that occurred in the early solar system.


American Mineralogist | 2014

Steinhardtite, a new body-centered-cubic allotropic form of aluminum from the Khatyrka CV3 carbonaceous chondrite

Luca Bindi; Nan Yao; Chaney Lin; Lincoln S. Hollister; Glenn J. MacPherson; Gerald R. Poirier; Christopher L. Andronicos; Vadim V. Distler; Michael P. Eddy; Alexander Kostin; Valery Kryachko; William M. Steinhardt; Marina A. Yudovskaya

Abstract Steinhardtite is a new mineral from the Khatyrka meteorite; it is a new allotropic form of aluminum. It occurs as rare crystals up to ~10 μm across in meteoritic fragments that contain evidence of a heterogeneous distribution of pressures and temperatures during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200 °C. The meteorite fragments contain the high-pressure phases ahrensite, coesite, stishovite, and an unnamed spinelloid with composition Fe3-xSixO4 (x ≈ 0.4). Other minerals include trevorite, Ni-Al-Mg-Fe spinels, magnetite, diopside, forsterite, clinoenstatite, nepheline, pentlandite, Cu-bearing troilite, icosahedrite, khatyrkite, cupalite, taenite, and Al-bearing taenite. Given the exceedingly small grain size of steinhardtite, it was not possible to determine most of the physical properties for the mineral. A mean of 9 electron microprobe analyses (obtained from two different fragments) gave the formula Al0.38Ni0.32Fe0.30, on the basis of 1 atom. A combined TEM and single-crystal X‑ray diffraction study revealed steinhardtite to be cubic, space group Im3m, with a = 3.0214(8) Å, and V = 27.58(2) Å3, Z = 2. In the crystal structure [R1 = 0.0254], the three elements are disordered at the origin of the unit cell in a body-centered-cubic packing (α-Fe structure type). The five strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 2.1355 (100) (110); 1.5100 (15) (200); 1.2329 (25) (211); 0.9550 (10) (310); 0.8071 (30) (321). The new mineral has been approved by the IMA-NMNC Commission (2014-036) and named in honor of Paul J. Steinhardt, Professor at the Department of Physics of Princeton University, for his extraordinary and enthusiastic dedication to the study of the mineralogy of the Khatyrka meteorite, a unique CV3 carbonaceous chondrite containing the first natural quasicrystalline phase icosahedrite. The recovery of the polymorph of Al described here that contains essential amounts of Ni and Fe suggests that Al could be a contributing candidate for the anomalously low density of the Earth’s presumed Fe-Ni core.


American Mineralogist | 2015

Decagonite, Al71Ni24Fe5, a quasicrystal with decagonal symmetry from the Khatyrka CV3 carbonaceous chondrite

Luca Bindi; Nan Yao; Chaney Lin; Lincoln S. Hollister; Christopher L. Andronicos; Vadim V. Distler; Michael P. Eddy; Alexander Kostin; Valery Kryachko; Glenn J. MacPherson; William M. Steinhardt; Marina A. Yudovskaya; Paul J. Steinhardt

Abstract Decagonite is the second natural quasicrystal, after icosahedrite (Al63Cu24Fe13), and the first to exhibit the crystallographically forbidden decagonal symmetry. It was found as rare fragments up to ~60 mm across in one of the grains (labeled number 126) of the Khatyrka meteorite, a CV3 carbonaceous chondrite. The meteoritic grain contains evidence of a heterogeneous distribution of pressures and temperatures that occurred during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200 °C. Decagonite is associated with Al-bearing trevorite, diopside, forsterite, ahrensite, clinoenstatite, nepheline, coesite, pentlandite, Cu-bearing troilite, icosahedrite, khatyrkite, taenite, Al-bearing taenite, and steinhardtite. Given the exceedingly small size of decagonite, it was not possible to determine most of the physical properties for the mineral. A mean of seven electron microprobe analyses (obtained from three different fragments) gave the formula Al70.2(3)Ni24.5(4)Fe5.3(2), on the basis of 100 atoms. A combined TEM and single-crystal X‑ray diffraction study revealed the unmistakable signature of a decagonal quasicrystal: a pattern of sharp peaks arranged in straight lines with 10-fold symmetry together with periodic patterns taken perpendicular to the 10-fold direction. For quasicrystals, by definition, the structure is not reducible to a single three-dimensional unit cell, so neither cell parameters nor Z can be given. The likely space group is P105/mmc, as is the case for synthetic Al71Ni24Fe5. The five strongest powder-diffraction lines [d in Å (I/I0)] are: 2.024 (100), 3.765 (50), 2.051 (45), 3.405 (40), 1.9799 (40). The new mineral has been approved by the IMA-NMNC Commission (IMA2015-017) and named decagonite for the 10-fold symmetry of its structure. The finding of a second natural quasicrystal informs the longstanding debate about the stability and robustness of quasicrystals among condensed matter physicists and demonstrates that mineralogy can continue to surprise us and have a strong impact on other disciplines.


Geology | 2017

Timing of initial seafloor spreading in the Newfoundland-Iberia rift

Michael P. Eddy; Oliver Jagoutz; Mauricio Ibanez-Mejia

Broad areas of subcontinental lithospheric mantle are commonly exposed along ocean-continent transition zones in magma-poor rifts and are thought to be exhumed along lithospheric-scale detachment faults during the final stages of rifting. However, the nature of the transition from final rifting to seafloor spreading is controversial. We present the first high-precision U-Pb zircon geochronologic and Hf isotopic data from gabbros that intrude exhumed mantle at Ocean Drilling Program (ODP) Sites 1070 and 1277 in the Newfoundland-Iberia rift (North Atlantic). The sites are conjugate to one another within crust that is commonly considered to have been emplaced during early seafloor spreading. Magnetic data suggest that crustal accretion occurred at both sites during magnetic polarity chrons M3–M0 (130–126 Ma). However, our data indicate that asthenospheric melts were emplaced over brief intervals (≤1 m.y.) prior to or coeval with mantle exhumation at 124 Ma at ODP Site 1070 and 115 Ma at ODP Site 1277. We suggest that this discrepancy is the result of continued mantle exhumation along large, west-dipping detachment faults until lithospheric breakup. The breakup location is likely coincident with the large-amplitude magnetic J anomaly, and our 115 Ma date for magmatism within this anomaly provides the best available age constraint for breakup along the studied transect.


Geology | 2016

Rapid assembly and crystallization of a fossil large-volume silicic magma chamber

Michael P. Eddy; Samuel A. Bowring; Robert B. Miller; Jeffrey H. Tepper

The rates at which large volumes of eruptible, silicic (>65 wt% SiO2) magma (magma chambers) are assembled, as well as their longevity in the upper crust, remain controversial. This controversy is due, in part, to a missing record of granitoid plutonic complexes that represent large fossil upper crustal magma chambers. We present new geologic mapping and high-precision U-Pb zircon geochronology from the Eocene Golden Horn batholith in Washington State, USA. These data reveal that the batholith was constructed as a series of sills over 739 ± 34 k.y. Topographic relief of >2 km permits volume estimates for 4 of the sills, the largest of which, a >424 km3 rapakivi granite, was emplaced over 26 ± 25 k.y. at a rate of ∼0.0125 km3/yr. This rate exceeds those needed to build large, silicic magma chambers in thermal models, and we suggest that that this unit may represent the first fossil magma chamber of this type recognized in the geologic record.


Geological Society of America Bulletin | 2016

High-resolution temporal and stratigraphic record of Siletzia’s accretion and triple junction migration from nonmarine sedimentary basins in central and western Washington

Michael P. Eddy; Samuel A. Bowring; Paul J. Umhoefer; Robert B. Miller; Noah McLean; Erin E. Donaghy

The presence of early Eocene near-trench magmatism in western Washington and southern British Columbia has led to speculation that this area experienced ridge-trench interaction during that time. However, the effects of this process as they are preserved in other parts of the geologic record are poorly known. We present high-precision U-Pb zircon geochronology from Paleogene nonmarine sedimentary and volcanic sequences in central and western Washington that preserve a record of tectonic events between ca. 60 and 45 Ma. The data reveal that the Swauk, Chuckanut, and Manastash Formations formed a nonmarine sedimentary basin along the North American margin between ≤59.9 and 51.3 Ma. This basin experienced significant disruption that culminated in basinwide deformation, uplift, and partial erosion during accretion of the Siletzia terrane between 51.3 and 49.9 Ma. Immediately following accretion, dextral strike-slip faulting began, or accelerated, on the Darrington–Devil’s Mountain, Entiat, Leavenworth, Eagle Creek, and Straight Creek–Fraser fault zones between 50 and 46 Ma. During this time, the Chumstick Formation was deposited in a strike-slip basin coeval with near-trench magmatism. Faulting continued on the Entiat, Eagle Creek, and Leavenworth faults until a regional sedimentary basin was reestablished ≤45.9 Ma, and may have continued on the Straight Creek–Fraser fault until 35–30 Ma. This record of basin disruption, volcanism, and strike-slip faulting is consistent with ridge-trench interaction and supports the presence of an oceanic spreading ridge at this latitude along the North American margin during the early Eocene.


Lithosphere | 2017

Age and volcanic stratigraphy of the Eocene Siletzia oceanic plateau in Washington and on Vancouver Island

Michael P. Eddy; Kenneth P. Clark; Michael Polenz

Geophysical, geochemical, geochronologic, and stratigraphic observations all suggest that the basalts that underlie western Oregon and Washington (USA), and southern Vancouver Island (Canada) form a coherent terrane of Eocene age, named Siletzia. The total volume of basalt within Siletzia is comparable to that observed in large igneous provinces and several lines of evidence point toward the terrane’s origin as an accreted oceanic plateau. However, a thick sequence of continentally derived turbidites, named the Blue Mountain unit, has long been considered to floor the northern part of the terrane and its presence has led to alternative hypotheses in which Siletzia was built on the continental margin. We present new high-precision U-Pb zircon dates from silicic tuffs and intrusive rocks throughout the basaltic basement of northern Siletzia, as well as detrital zircon age spectra and maximum depositional ages for the Blue Mountain unit to help clarify the volcanic stratigraphy of this part of the terrane. These dates show that northern Siletzia was emplaced between 53.18 ± 0.17 Ma and 48.364 ± 0.036 Ma, similar to the age and duration of magmatism in the central and southern parts of the terrane. Turbidites in the basal Blue Mountain unit have maximum depositional ages as young as 44.72 ± 0.21 Ma and are distinctly younger than the basaltic basement that forms Siletzia. This age relationship implies that they were thrust under the terrane after 44.72 ± 0.21 Ma along one or more enigmatic faults. The younger age for these sedimentary rocks no longer requires construction of Siletzia on the continental margin, and we consider our revised stratigraphy to provide further support for the origin of the terrane as an accreted oceanic plateau.

Collaboration


Dive into the Michael P. Eddy's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Vadim V. Distler

Russian Academy of Sciences

View shared research outputs
Top Co-Authors

Avatar

Valery Kryachko

Russian Academy of Sciences

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Marina A. Yudovskaya

University of the Witwatersrand

View shared research outputs
Researchain Logo
Decentralizing Knowledge