Magnetic fabrics of the Bloodgood Canyon and Shelley Peak Tuffs, southwestern New Mexico: implications for emplacement and alteration processes

Seaman, S. J.; McIntosh, William C.; Geissman, J. W.; Williams, Michael L.; Elston, Wolfgang E.

doi:10.1007/bf00258185

Cited by 46 publications

(27 citation statements)

References 26 publications

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“…Moreover, the transportation and deposition can be highly variable ranging from concentrated and laminar flows to turbulent currents. However, many studies showed that pyroclastic flows have the ability to preserve in their fabric imprints of the flow direction during their emplacement, as well as information on the vent position (Knight et al 1986, Hillhouse SWells 1991, Seaman et al 1991, MacDonald et al 1992, Cagnoli & Tarling 1997). …”

Section: Pyroclastic Flowsmentioning

confidence: 99%

“…More recently the use of the AMS technique has been extended in undeformed ignim brites, as a flow fabric delineator (Seaman et al 1991, Lamarche & Froggatt 1993, Palmer et al 1996, Palmer & MacDonald 1999. In a recent study by Wang et al (2001) the magnetic anisotropy has been also used in order to check whether some stratigraphically and geochemically similar units originated from the same source.…”

Section: Ignimbritesmentioning

confidence: 99%

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Anisotropy of Magnetic Susceptibility (Ams) in Volcanic Formations: Theory and Preliminary Results From Recent Volcanics of Broader Aegean.

Zananiri

Kondopoulou

2004

geosociety

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The anisotropy of magnetic susceptibility (AMS) is a physical property of rocks widely used in petrofabric studies and other applications. It is based on the measurement of low-field magnetic susceptibility in different directions along a sample. From this process several scalar properties arise, defining the magnitude and symmetry of the AMS ellipsoid, along with the magnetic foliation, namely the magnetic fabric. Imaging the sense of magma flow in dykes is an important task for volcanology; the magnetic fabric provides a fast and accurate way to infer this flow direction. Moreover, the AMS technique can be used in order to distinguish sills and dykes, a task that is almost impossible by using only field observations. Finally in the case of lava flows, the method can be applied to define the local flow conditions and to indicate the position of the "paleo" source region. However, this technique is quite new in Greece. Some preliminary results from volcanic formations of continental Greece and Southern Aegean are presented (Aegina, Almopia, Elatia, Gavra, Kos, Patmos, Samos, Samothraki and Santorini).

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Section: Pyroclastic Flowsmentioning

confidence: 99%

Section: Ignimbritesmentioning

confidence: 99%

Anisotropy of Magnetic Susceptibility (Ams) in Volcanic Formations: Theory and Preliminary Results From Recent Volcanics of Broader Aegean.

Zananiri

Kondopoulou

2004

geosociety

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“…Some authors (MacDonald and Palmer, 1990;Seaman et al, 1991) compared AMS data from ignimbrites with petrographic and field observations and recognized that AMS provides a precise and significantly faster means of approximating the transport direction of ignimbritic deposits than techniques based on macroscopic examination. It is established that the heterogeneous character of an ignimbritic deposits does not really affect the AMS fabric and that this method provides a realistic indication of the flow direction (Wolff et al, 1989).…”

Section: Sampling Methods and Ams Measurementsmentioning

confidence: 99%

“…The K 1 axis is usually interpreted to be parallel to the flow direction and thus plunges towards the source (Knight et al, 1986). The use of the K 1 axis alone as a proxy for flow direction is not always reliable (Seaman et al, 1991;Hillhouse and Wells, 1991;Ort, 1993;Le Pennec et al, 1998) and a different methodology must be used to interpret the magnetic data. The imbrication angle of the magnetic foliation plane, which equivalents the deviation of the K 3 axes from the normal to the macroscopic flow plane, offers another method to distinguish the flow direction of ignimbrite (Henry, 1980;Thompson and Oldfield, 1986) (Fig.…”

Section: Sampling Methods and Ams Measurementsmentioning

confidence: 99%

Hazards from Pyroclastic Density Currents at Mount Bamenda (West-Cameroon, Cameroon Volcanic Line): Mapping and Assessment by AMS Method

Dedzo¹,

Kamgang²,

Njonfang³

et al. 2015

American Journal of Geoscience

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Hazards related to pyroclastic density current continue to raise victims on many volcanoes in our planet. The Cameroon is not spared to this type of hazard because deposits of pyroclastic flows and surges are found on Mount Bamenda; products of this volcano are relatively young (27-0 Ma). Besides Mount Bamenda, Mounts Bambouto and Oku are the only volcanoes located in the central part of the Cameroon Volcanic Line where these ignimbritic deposits are found. Several factors highlight dangerousness and damage that can cause ignimbritic flows on the flanks of this volcano. This is essentially the high aspect ratio of these ignimbrites, the important population (about 750,000 people) that lives on the slopes and around the volcano. In order to have an idea of a nowadays ignimbritic eruption scenario on Bamenda volcano, the Anisotropy of Magnetic Susceptibility (ASM) method is used in this study to highlight the palaeoflow in ancient deposits of ignimbrites which are mostly discontinuous and isotropic. Results of AMS study are used to produce map of hazards and assess risks that may be related with such eruptions in Bamenda volcano.

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“…The credibility of the AMS fabric as a paleocurrent and depositional indicator is known from work on natural (Ellwood and Ledbetter, 1979;Abdeldayem et al, 1999;Liu et al, 2001) and laboratory deposited sediments (Rees, 1965;Rees and Woodall, 1975). Furthermore, AMS has been used to evaluate flow vectors in lava flows (Cañón-Tapia et al, 1996Cañón-Tapia and Walker, 1998;MacDonald et al, 1992) and pyroclastic deposits (e.g., Ellwood, 1982;Incoronato et al, 1983;Knight et al, 1986;Wolff et al, 1989;MacDonald and Palmer, 1990;Hillhouse and Wells, 1991;Seaman et al, 1991;Ort, 1993;Cagnoli and Tarling, 1997;MacDonald et al, 1998;Ort et al, 1999), in order to determine vent locations, or transport and depositional processes at different distances from the vent (e.g., Fisher et al, 1993;Baer et al, 1997;Le Pennec et al, 1998;Palmer and MacDonald, 1999).…”

mentioning

confidence: 99%

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Lenhardt

Böhnel

Hinderer

et al. 2013

Sedimentary Geology

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Sources of ancient volcanic rocks are often unknown if they are either eroded and/or covered by younger deposits. This problem, as well as the provenance of reworked volcaniclastic, fluvial and mass-flow deposits, can be partially solved by the application of anisotropy of the magnetic susceptibility (AMS). For massive and poorly sorted volcaniclastic rocks in particular this may be the only way of finding reliable transport directions and therefore allowing for paleogeographic reconstructions. Here, we present a data set of 428 AMS measurements and 249 measurements of sedimentary paleocurrent indicators from the Miocene Tepoztlán Formation at the southern edge of the Transmexican Volcanic Belt (Central Mexico). The highest degree of reliability of AMS measurements is gained for data from lava samples and the lowest from mass flows. Sedimentary structures in sandstones and conglomerates such as trough cross-stratification, asymmetric ripple marks, and the shape of scours and channels could be used to calibrate the results from AMS data and to prove their reliability. AMS data on fluvial deposits point to a drainage system with a W-E flow direction, indicating an outflow of the river system into the ancient Gulf of Mexico.Keywords: Anisotropy of magnetic susceptibility; paleocurrent direction; volcaniclastic; Transmexican Volcanic Belt; Miocene; Mexico 3 In ancient volcanic settings, one challenge in the investigation of volcanic and volcaniclastic deposits is the determination of source vent locations, since former volcanic centers may be either eroded and/or covered by younger deposits. Furthermore, the determination of the provenance of fluvial and mass-flow deposits, arising from the volcanic ring plain itself (Manville et al., 2009, and references therein) or rivers in distal reaches, can also be problematic. In lava flows, both vesicle and crystal preferred orientations have been used extensively for this purpose (e.g., Waters, 1960;Smith and Rhodes, 1972;Walker, 1989;Cashman and Kauahikaua, 1997;Manga, 1998;Iezzi and Ventura, 2002). However, petrological structures such as foliation and lineation due to the movement of a lava flow are often difficult to observe and measure (Bascou et al., 2005). Massive pyroclastic rocks such as ignimbrites and block-and-ash flow deposits rarely show any measurable alignment or structure that can help determine flow direction. However, the magnetic fabric can be used to determine their paleocurrent direction, and the speed, precision, cheapness and range of applicability make it unique in this regard (Tarling and Hrouda, 1993).All materials, even if they do not acquire remanent magnetization, have a magnetic susceptibility (Liu et al., 2001), which is not always isotropic in the rock (Ising, 1942). This spatial susceptibility variation is defined as the anisotropy of magnetic susceptibility (AMS) and reflects the preferred orientation of magnetic minerals in the rock or sediments, i.e. its magnetic fabric (Hrouda, 1982;Tarling and Hrouda, 1993), which yields thr...

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Magnetic fabrics of the Bloodgood Canyon and Shelley Peak Tuffs, southwestern New Mexico: implications for emplacement and alteration processes

Cited by 46 publications

References 26 publications

Anisotropy of Magnetic Susceptibility (Ams) in Volcanic Formations: Theory and Preliminary Results From Recent Volcanics of Broader Aegean.

Anisotropy of Magnetic Susceptibility (Ams) in Volcanic Formations: Theory and Preliminary Results From Recent Volcanics of Broader Aegean.

Hazards from Pyroclastic Density Currents at Mount Bamenda (West-Cameroon, Cameroon Volcanic Line): Mapping and Assessment by AMS Method

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

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