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Anatomy of an Ignimbrite: Stratigrap...

Gallo, Rose.

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Anatomy of an Ignimbrite: Stratigraphy and Flow Processes of the Campanian Ignimbrite.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Anatomy of an Ignimbrite: Stratigraphy and Flow Processes of the Campanian Ignimbrite./
Author:	Gallo, Rose.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
Description:	170 p.
Notes:	Source: Masters Abstracts International, Volume: 81-12.
Contained By:	Masters Abstracts International81-12.
Subject:	Geology. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27962540
ISBN:	9798641426815

Anatomy of an Ignimbrite: Stratigraphy and Flow Processes of the Campanian Ignimbrite.
Gallo, Rose.

Anatomy of an Ignimbrite: Stratigraphy and Flow Processes of the Campanian Ignimbrite. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 170 p.

Source: Masters Abstracts International, Volume: 81-12.

Thesis (M.S.)--Northern Arizona University, 2020.

This item must not be sold to any third party vendors.

The Campanian Ignimbrite was emplaced during the first caldera-forming eruption of Campi Flegrei near Naples, Italy. The 39-ka ignimbrite is found up to 80 km from the caldera and co-ignimbrite ash-fall deposits are found more than 2300 km away. The pyroclastic density current was dilute and mobile; Campanian Ignimbrite crops out on mountains a kilometer in elevation as much as 60 km from the caldera. Stratigraphic units within the proximal and distal deposits of the Campanian Ignimbrite have never been definitively correlated due to their dissimilar appearances and the lack of medial exposure. Determining which of the proximal units was emplaced simultaneously with the distal deposits is necessary to understand the eruptive events. This thesis supports the hypothesis that the Welded Grey Ignimbrite, the most voluminous distal facies correlates in part with a high grade ignimbrite in the proximal deposits called the Piperno, but also contains materials representing a significant eruptive phase which produced no proximal deposits. The overlying distal facies, the Lithified Yellow Tuff is proposed to correlate with the Breccia Unit, a co-ignimbrite lag breccia. The two other proximal units, the Lower and Upper Pumice Flow Units, appear to have no distal correlates.Major-element geochemistry of glass shards from the ignimbrite matrix, shard morphology, lithic clast componentry and the presence or absence of magnetite and obsidian are used to compare the proximal and distal deposits for correlation. The Piperno and the Welded Grey Ignimbrite show similar major-element trends that are distinct from the patterns of the other units while the Lithified Yellow Tuff is more comparable with the Breccia Unit. Seven varieties of glass-shard shapes were identified of which most are found in several different units. The proportions of different shard types in each sample connects the Lithified Yellow Tuff with the Breccia Unit. The shard types of some outcrops of the Welded Grey Ignimbrite resemble the Piperno, some resemble the Breccia Unit and some are not comparable to any known proximal outcrop. Bubble-wall shards in particular are concentrated in the highest-elevation distal outcrops and in the co-ignimbrite, but not in the proximal outcrops. This may show that the high-elevation outcrops were deposited from the dilute upper portion of the PDC while lower-elevation outcrops were deposited from the denser basal layer of the PDC where pumice shards may have formed by abrasion of pumice lapilli. The Welded Grey Ignimbrite shares several lithic types with both the Piperno and Breccia Unit, and the Lithified Yellow Tuff shares a set of lithic types with the Breccia Unit that is mutually exclusive with those it shares with the Welded Grey Ignimbrite. Obsidian is totally absent in the fallout deposits of the eruption and the lower units of the Ignimbrite, including the Piperno and Welded Grey Ignimbrite. Magnetite is absent in some samples of the Piperno and Welded Grey Ignimbrite, but present in all samples of all other units. The Lithified Yellow Tuff uniformly shares the measured characteristics with the Breccia Unit. The Welded Grey Ignimbrite has some outcrops that share all measured characteristics with the Piperno, but most outcrops have a combination of characteristics similar to the Piperno and the Breccia Unit that could not be produced by physical mixing of flow lobes. These deposits are hypothesized to represent an eruptive phase occurring between the Piperno and Breccia Unit that is not recorded in the proximal deposits.

ISBN: 9798641426815Subjects--Topical Terms:

516570
Geology.
Subjects--Index Terms:

Ash component analysis

Anatomy of an Ignimbrite: Stratigraphy and Flow Processes of the Campanian Ignimbrite.
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245 1 0 $a Anatomy of an Ignimbrite: Stratigraphy and Flow Processes of the Campanian Ignimbrite.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2020
300 $a 170 p.
500 $a Source: Masters Abstracts International, Volume: 81-12.
500 $a Advisor: Ort, Michael H.
502 $a Thesis (M.S.)--Northern Arizona University, 2020.
506 $a This item must not be sold to any third party vendors.
520 $a The Campanian Ignimbrite was emplaced during the first caldera-forming eruption of Campi Flegrei near Naples, Italy. The 39-ka ignimbrite is found up to 80 km from the caldera and co-ignimbrite ash-fall deposits are found more than 2300 km away. The pyroclastic density current was dilute and mobile; Campanian Ignimbrite crops out on mountains a kilometer in elevation as much as 60 km from the caldera. Stratigraphic units within the proximal and distal deposits of the Campanian Ignimbrite have never been definitively correlated due to their dissimilar appearances and the lack of medial exposure. Determining which of the proximal units was emplaced simultaneously with the distal deposits is necessary to understand the eruptive events. This thesis supports the hypothesis that the Welded Grey Ignimbrite, the most voluminous distal facies correlates in part with a high grade ignimbrite in the proximal deposits called the Piperno, but also contains materials representing a significant eruptive phase which produced no proximal deposits. The overlying distal facies, the Lithified Yellow Tuff is proposed to correlate with the Breccia Unit, a co-ignimbrite lag breccia. The two other proximal units, the Lower and Upper Pumice Flow Units, appear to have no distal correlates.Major-element geochemistry of glass shards from the ignimbrite matrix, shard morphology, lithic clast componentry and the presence or absence of magnetite and obsidian are used to compare the proximal and distal deposits for correlation. The Piperno and the Welded Grey Ignimbrite show similar major-element trends that are distinct from the patterns of the other units while the Lithified Yellow Tuff is more comparable with the Breccia Unit. Seven varieties of glass-shard shapes were identified of which most are found in several different units. The proportions of different shard types in each sample connects the Lithified Yellow Tuff with the Breccia Unit. The shard types of some outcrops of the Welded Grey Ignimbrite resemble the Piperno, some resemble the Breccia Unit and some are not comparable to any known proximal outcrop. Bubble-wall shards in particular are concentrated in the highest-elevation distal outcrops and in the co-ignimbrite, but not in the proximal outcrops. This may show that the high-elevation outcrops were deposited from the dilute upper portion of the PDC while lower-elevation outcrops were deposited from the denser basal layer of the PDC where pumice shards may have formed by abrasion of pumice lapilli. The Welded Grey Ignimbrite shares several lithic types with both the Piperno and Breccia Unit, and the Lithified Yellow Tuff shares a set of lithic types with the Breccia Unit that is mutually exclusive with those it shares with the Welded Grey Ignimbrite. Obsidian is totally absent in the fallout deposits of the eruption and the lower units of the Ignimbrite, including the Piperno and Welded Grey Ignimbrite. Magnetite is absent in some samples of the Piperno and Welded Grey Ignimbrite, but present in all samples of all other units. The Lithified Yellow Tuff uniformly shares the measured characteristics with the Breccia Unit. The Welded Grey Ignimbrite has some outcrops that share all measured characteristics with the Piperno, but most outcrops have a combination of characteristics similar to the Piperno and the Breccia Unit that could not be produced by physical mixing of flow lobes. These deposits are hypothesized to represent an eruptive phase occurring between the Piperno and Breccia Unit that is not recorded in the proximal deposits.
590 $a School code: 0391.
650 4 $a Geology. $3 516570
650 4 $a Geophysics. $3 535228
653 $a Ash component analysis
653 $a Campanian Ignimbrite
653 $a Ignimbrite stratigraphy
653 $a Pyroclastic density current
653 $a Shard chemistry
653 $a Shard shape
690 $a 0372
690 $a 0373
710 2 $a Northern Arizona University. $b SESES - Geology. $3 3556408
773 0 $t Masters Abstracts International $g 81-12.
790 $a 0391
791 $a M.S.
792 $a 2020
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27962540