Professor in Geophysics at Univesity of Sao Paulo, Brazil. My main interests are Geomagnetism and Paleomagnetism. Address: Rua do Matão 1226 Sao Paulo - SP - Brasil
The end-Triassic extinction is one of the Phanerozoic’s largest mass extinctions. This extinction... more The end-Triassic extinction is one of the Phanerozoic’s largest mass extinctions. This extinction is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP). However, recent work suggests that the earliest known CAMP basalts occur above the extinction horizon and that climatic and biotic changes began before the earliest known CAMP eruptions. Here we present new high-precision U-Pb ages from CAMP mafic intrusive units, showing that magmatic activity was occurring ∼100 Kyr ago before the earliest known eruptions. We correlate the early magmatic activity with the onset of changes to the climatic and biotic records. We also report ages from sills in an organic rich sedimentary basin in Brazil that intrude synchronously with the extinction suggesting that degassing of these organics contributed to the climate change which drove the extinction. Our results indicate that the intrusive record from large igneous pro...
This work presents an extensive directional paleomagnetic database of the Kiaman reversed superch... more This work presents an extensive directional paleomagnetic database of the Kiaman reversed superchron. It is composed of 1,459 paleomagnetic directions from igneous rocks corresponding to 91 data sets (or paleomagnetic poles). An almost constant behavior of more concentrated and circular distributions for latitudes higher than 10° was found, which contrasts strongly with predictions of the representative models for the past few million years. We searched for simplified and spatially covariant Giant Gaussian Process (GGP) models that best explain the directional distribution of the Kiaman database. We used the mean strength based on the mean of virtual dipole moment (VDM) results for the period drawn from the available databases. Among the tested models, the one that best explains the directional paleosecular variation of the Kiaman database is the covariant type. According to this model, the correlations between the Gaussian coefficients are valid for the last 10 Myr and the Kiaman superchron. The resulting GGP models have β parameters similar to the 0–10 Ma models, which indicates that the relation between symmetric and antisymmetric families appears unchanged in the geological past. The relative variability of the Kiaman field, as inferred from the ratio αg10¯ from GGP models, is lower than for the past 10 Myr. Thus, as well as the paleointensity, αg10¯ seems to be a proxy that can be used for evaluating the geomagnetic development along the geological time.
The Penatecaua magmatism (~201 Ma) is part of the Central Atlantic Magmatic Province (CAMP) and i... more The Penatecaua magmatism (~201 Ma) is part of the Central Atlantic Magmatic Province (CAMP) and is represented by voluminous sills in the Amazonas Basin, north Brazil. The sills appear south of the Amazonas River, particularly in the Medicilândia, Placas, and Rurópolis cities. To the north of the river, near Monte Alegre and Alenquer, smaller sills and NNE-SSW dikes prevail. Paleomagnetic data from 28 sampling sites of sills and dikes from all areas gave consistent results of normal polarity. Despite the large area of occurrence, the VGPs show small dispersion, consistent with a very brief emplacement time, as indicated by the radiometric ages. However, some sites, mainly from Alenquer and the southern sills, gave anomalous directions that may represent the record of a transitional geomagnetic field. The calculated paleomagnetic pole includes former data from Guerreiro and Schult (1986) plotting at 260.1 • E 77.5 • S (N = 30; A 95 = 3.8 • ; k = 48) and agrees with other high-quality CAMP poles for South America.
The end-Triassic extinction is one of the Phanerozoic’s largest mass extinctions. This extinction... more The end-Triassic extinction is one of the Phanerozoic’s largest mass extinctions. This extinction is typically attributed to climate change associated with degassing of basalt flows from the central Atlantic magmatic province (CAMP). However, recent work suggests that the earliest known CAMP basalts occur above the extinction horizon and that climatic and biotic changes began before the earliest known CAMP eruptions. Here we present new high-precision U-Pb ages from CAMP mafic intrusive units, showing that magmatic activity was occurring ∼100 Kyr ago before the earliest known eruptions. We correlate the early magmatic activity with the onset of changes to the climatic and biotic records. We also report ages from sills in an organic rich sedimentary basin in Brazil that intrude synchronously with the extinction suggesting that degassing of these organics contributed to the climate change which drove the extinction. Our results indicate that the intrusive record from large igneous pro...
This work presents an extensive directional paleomagnetic database of the Kiaman reversed superch... more This work presents an extensive directional paleomagnetic database of the Kiaman reversed superchron. It is composed of 1,459 paleomagnetic directions from igneous rocks corresponding to 91 data sets (or paleomagnetic poles). An almost constant behavior of more concentrated and circular distributions for latitudes higher than 10° was found, which contrasts strongly with predictions of the representative models for the past few million years. We searched for simplified and spatially covariant Giant Gaussian Process (GGP) models that best explain the directional distribution of the Kiaman database. We used the mean strength based on the mean of virtual dipole moment (VDM) results for the period drawn from the available databases. Among the tested models, the one that best explains the directional paleosecular variation of the Kiaman database is the covariant type. According to this model, the correlations between the Gaussian coefficients are valid for the last 10 Myr and the Kiaman superchron. The resulting GGP models have β parameters similar to the 0–10 Ma models, which indicates that the relation between symmetric and antisymmetric families appears unchanged in the geological past. The relative variability of the Kiaman field, as inferred from the ratio αg10¯ from GGP models, is lower than for the past 10 Myr. Thus, as well as the paleointensity, αg10¯ seems to be a proxy that can be used for evaluating the geomagnetic development along the geological time.
The Penatecaua magmatism (~201 Ma) is part of the Central Atlantic Magmatic Province (CAMP) and i... more The Penatecaua magmatism (~201 Ma) is part of the Central Atlantic Magmatic Province (CAMP) and is represented by voluminous sills in the Amazonas Basin, north Brazil. The sills appear south of the Amazonas River, particularly in the Medicilândia, Placas, and Rurópolis cities. To the north of the river, near Monte Alegre and Alenquer, smaller sills and NNE-SSW dikes prevail. Paleomagnetic data from 28 sampling sites of sills and dikes from all areas gave consistent results of normal polarity. Despite the large area of occurrence, the VGPs show small dispersion, consistent with a very brief emplacement time, as indicated by the radiometric ages. However, some sites, mainly from Alenquer and the southern sills, gave anomalous directions that may represent the record of a transitional geomagnetic field. The calculated paleomagnetic pole includes former data from Guerreiro and Schult (1986) plotting at 260.1 • E 77.5 • S (N = 30; A 95 = 3.8 • ; k = 48) and agrees with other high-quality CAMP poles for South America.
Time variations in the magnetic record of lake sediments are reexamined in this paper by applying... more Time variations in the magnetic record of lake sediments are reexamined in this paper by applying a new method for spectral analysis of time series irregularly sampled. The method produces a combination of all the spectra by means of a modified version of the Lomb-Scargle periodogram. This combination of information approach is a stacking-like procedure reducing noise and highlighting features that may be not sufficiently clear in individual spectrum. We investigated the magnetic declination and inclination records from 17 lakes from Argentina, Australia, North America and Greece limited to the first 10,000 years. The combination of the periodograms from the investigated lakes showed some high correlation maxima in the range ~1400-1700 yr. for declinations and ~2100-2800 yr. for inclinations, although individually the subsets by country may display slight different intervals. The velocities of virtual geomagnetic pole displacement were investigated by the same method and gave spectral features in the same range (1500-2600 yr.), consistent with the directional data. These results were already reported in literature. However, the method turned out efficient in bringing common features from individual spectra supposed to express the same phenomena, as the operations perform the combination of uncertainties in the means.
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Papers by Marcia Ernesto
new method for spectral analysis of time series irregularly sampled. The method produces a combination
of all the spectra by means of a modified version of the Lomb-Scargle periodogram. This combination of
information approach is a stacking-like procedure reducing noise and highlighting features that may be
not sufficiently clear in individual spectrum. We investigated the magnetic declination and inclination
records from 17 lakes from Argentina, Australia, North America and Greece limited to the first 10,000
years. The combination of the periodograms from the investigated lakes showed some high correlation
maxima in the range ~1400-1700 yr. for declinations and ~2100-2800 yr. for inclinations, although
individually the subsets by country may display slight different intervals. The velocities of virtual
geomagnetic pole displacement were investigated by the same method and gave spectral features in the
same range (1500-2600 yr.), consistent with the directional data. These results were already reported in
literature. However, the method turned out efficient in bringing common features from individual spectra
supposed to express the same phenomena, as the operations perform the combination of uncertainties in
the means.