國立虎尾科技大學 |

Investigating the Potential Influences on Changes in Impact Spherule Diameters Between Correlated Layers Throughout the Archean

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Investigating the Potential Influences on Changes in Impact Spherule Diameters Between Correlated Layers Throughout the Archean/ Sean Becker.
Author:	Becker, Sean,
Description:	1 electronic resource (389 pages)
Notes:	Source: Masters Abstracts International, Volume: 86-12.
Contained By:	Masters Abstracts International86-12.
Subject:	Plate tectonics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31936809
ISBN:	9798315795353

Investigating the Potential Influences on Changes in Impact Spherule Diameters Between Correlated Layers Throughout the Archean
Becker, Sean,

Investigating the Potential Influences on Changes in Impact Spherule Diameters Between Correlated Layers Throughout the Archean [eletronic resource] /Sean Becker. - 1 electronic resource (389 pages)

Source: Masters Abstracts International, Volume: 86-12.

Impact spherule layers form from large impact events, which vaporize target rock and meteorite material which subsequently condenses into spherical ejecta particles termed spherules. Spherule layers can be deposited on global scales, making them exceptional stratigraphic markers, and are especially relevant to Archean rocks that were deposited during a time when Earth experienced a higher frequency of bombardment. This study uses petrographic imaging methods and considers a sequence of four impact events deposited from 3.47-2.49 Ga, which have been correlated between the Pilbara Craton of Western Australia (WA) and the Kaapvaal Craton of South Africa (SA), to assess temporal and spatial changes in spherule size distribution as a means to evaluate to relative distance between the cratons and the history of tectonic spreading between them. Thin sections of 55 samples from the nine spherule layers associated with these four impacts were photographed in their entirety and all the spherules counted and measured for short and long axis to calculate a representative diameter. It is found that the average difference in spherule diameter increased through time (3.47 Ga event: 26 µm, 2.63 Ga event: 66 µm, 2.57 Ga event: 123 µm, 2.49 Ga event: 207 µm). Spherule size distribution graphs yield similar findings, and each correlated spherule layer for an impact event has a range within 200 µm (3.47 Ga Western Australia: 1338 µm, 3.47 Ga South Africa: 1141 µm, 2.63 Ga WA: 1510 µm, 2.63 Ga SA: 1409 µm, 2.63 Ga WA: 1365 µm, 2.57 Ga WA: 911 µm, 2.57 Ga SA: 966 µm, 2.47 Ga WA: 1203 µm, 2.47 Ga SA: 1206 µm). Other potential influences on spherule diameter, such as petrologic type, depositional environment, bed thickness, and impactor size, have also been ruled out as controlling this difference in spherule diameter. These observed changes through time thus implicate a corresponding change in distance from the impact site, and using this as a proxy for relative distance suggests that the Pilbara and Kaapvaal Cratons were progressively spreading from 3.47-2.49 Ga. This study concludes that the Pilbara and Kaapvaal Cratons were oriented as a "Vaalbara" supercontinent during the Paleoarchean, but had spread into individual landmasses by the Neoarchean, and provides invaluable evidence for plate tectonic activity during this phase of Earth's history.

English

ISBN: 9798315795353Subjects--Topical Terms:

782857
Plate tectonics.
Subjects--Index Terms:

Plate tectonic activity

Investigating the Potential Influences on Changes in Impact Spherule Diameters Between Correlated Layers Throughout the Archean
LDR:03853nam a22004213i 4500 001 1172915
005 20260622113224.5
006 m o d
007 cr|nu||||||||
008 260803s2025 miu||||||m |||||||eng d
020 $a 9798315795353
035 $a (MiAaPQD)AAI31936809
035 $a AAI31936809
040 $a MiAaPQD $b eng $c MiAaPQD $e rda
100 1 $a Becker, Sean, $e author. $3 1503552
245 1 0 $a Investigating the Potential Influences on Changes in Impact Spherule Diameters Between Correlated Layers Throughout the Archean $c Sean Becker. $h [eletronic resource] /
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2025
300 $a 1 electronic resource (389 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Masters Abstracts International, Volume: 86-12.
500 $a Advisors: Davatzes, Alexandra Committee members: Buynevich, Ilya V.; Terry, Dennis O.
502 $b M.S. $c Temple University $d 2025.
520 # $a Impact spherule layers form from large impact events, which vaporize target rock and meteorite material which subsequently condenses into spherical ejecta particles termed spherules. Spherule layers can be deposited on global scales, making them exceptional stratigraphic markers, and are especially relevant to Archean rocks that were deposited during a time when Earth experienced a higher frequency of bombardment. This study uses petrographic imaging methods and considers a sequence of four impact events deposited from 3.47-2.49 Ga, which have been correlated between the Pilbara Craton of Western Australia (WA) and the Kaapvaal Craton of South Africa (SA), to assess temporal and spatial changes in spherule size distribution as a means to evaluate to relative distance between the cratons and the history of tectonic spreading between them. Thin sections of 55 samples from the nine spherule layers associated with these four impacts were photographed in their entirety and all the spherules counted and measured for short and long axis to calculate a representative diameter. It is found that the average difference in spherule diameter increased through time (3.47 Ga event: 26 µm, 2.63 Ga event: 66 µm, 2.57 Ga event: 123 µm, 2.49 Ga event: 207 µm). Spherule size distribution graphs yield similar findings, and each correlated spherule layer for an impact event has a range within 200 µm (3.47 Ga Western Australia: 1338 µm, 3.47 Ga South Africa: 1141 µm, 2.63 Ga WA: 1510 µm, 2.63 Ga SA: 1409 µm, 2.63 Ga WA: 1365 µm, 2.57 Ga WA: 911 µm, 2.57 Ga SA: 966 µm, 2.47 Ga WA: 1203 µm, 2.47 Ga SA: 1206 µm). Other potential influences on spherule diameter, such as petrologic type, depositional environment, bed thickness, and impactor size, have also been ruled out as controlling this difference in spherule diameter. These observed changes through time thus implicate a corresponding change in distance from the impact site, and using this as a proxy for relative distance suggests that the Pilbara and Kaapvaal Cratons were progressively spreading from 3.47-2.49 Ga. This study concludes that the Pilbara and Kaapvaal Cratons were oriented as a "Vaalbara" supercontinent during the Paleoarchean, but had spread into individual landmasses by the Neoarchean, and provides invaluable evidence for plate tectonic activity during this phase of Earth's history.
546 $a English
590 $a School code: 0225
650 # 4 $a Plate tectonics. $3 782857
650 # 4 $a Geophysics. $3 686174
650 # 4 $a Geology. $3 670379
653 # # $a Plate tectonic activity
653 # # $a Precambrian
653 # # $a Spherule layers
653 # # $a Vaalbara
690 $a 0372
690 $a 0592
690 $a 0373
710 2 # $a Temple University. $b Geology. $e degree granting institution. $3 1503553
720 1 $a Davatzes, Alexandra $e degree supervisor.
773 0 # $t Masters Abstracts International $g 86-12.
790 $a 0225
791 $a M.S.
792 $a 2025
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31936809