Correlation and stratigraphy of the BKT-2 volcanic complex in west-central Afar, Ethiopia

Erin N. DiMaggio, Christopher Campisano, Ramon Arrowsmith, Kaye Reed, Carl C. Swisher, Charles A. Lockwood

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Located adjacent to the paleoanthropological site of Hadar in Afar, Ethiopia, the Ledi-Geraru project area preserves multiple tephra deposits within the Pliocene sediments of the hominin-bearing Hadar Formation. Tephra deposits of the Bouroukie Tuff 2 volcanic complex (BKT-2) are important regional markers, and here we provide correlations between the Hadar and Ledi-Geraru project areas using major-element glass chemistry, stratigraphic relationships, outcrop characteristics, and 40Ar/39Ar dates. These correlations greatly expand existing temporal and spatial resolution, aid in interpretations of regional depositional environments, and increase the documented extent of BKT-2 to ∼600 km2. BKT-2 exposures at Ledi-Geraru are the thickest and most complete yet observed. There, the BKT-2 complex is preserved as two air-fall lapilli layers, BKT-2U (<97 cm thick) and BKT-2L (<9 cm thick), separated by <2.5 m of silts and clays or diatomite that overlie the Green Marker Bed (GMB), a laminated ash tuff. Measured sections were evaluated to create a stratigraphy-based model of paleolandscape variations using BKT-2 tephra as laterally extensive isochronous surfaces. BKT-2 was mainly erupted into lacustrine and nearshore environments. The eastern Ledi-Geraru region was likely located at the depocenter of an expansive fluviolacustrine network. Representing the last major lacustrine phase of the Hadar Formation, lateral facies variations show the westward expansion of a lacustrine setting ca. 2.96 Ma followed by eastward regression initiated sometime prior to the eruption of BKT-2U ca. 2.94 Ma. High-resolution, well-correlated, and temporally constrained stratigraphic records are key to the interpretation of paleoenvironmental variation in East Africa.

Original languageEnglish (US)
Pages (from-to)163-177
Number of pages15
JournalSpecial Paper of the Geological Society of America
Volume446
DOIs
StatePublished - 2008

Fingerprint

tuff
stratigraphy
tephra
marker bed
nearshore environment
diatomite
lacustrine environment
depocenter
geological record
depositional environment
aid
Pliocene
outcrop
spatial resolution
ash
volcanic eruption
glass
clay
air
sediment

Keywords

  • Afar Depression
  • Hadar Formation
  • Paleoenvironment
  • Pliocene
  • Tephrochronology
  • Tephrostratigraphy

ASJC Scopus subject areas

  • Geology

Cite this

Correlation and stratigraphy of the BKT-2 volcanic complex in west-central Afar, Ethiopia. / DiMaggio, Erin N.; Campisano, Christopher; Arrowsmith, Ramon; Reed, Kaye; Swisher, Carl C.; Lockwood, Charles A.

In: Special Paper of the Geological Society of America, Vol. 446, 2008, p. 163-177.

Research output: Contribution to journalArticle

@article{e57ef26988b0414ebdee9e4d4e19aa69,
title = "Correlation and stratigraphy of the BKT-2 volcanic complex in west-central Afar, Ethiopia",
abstract = "Located adjacent to the paleoanthropological site of Hadar in Afar, Ethiopia, the Ledi-Geraru project area preserves multiple tephra deposits within the Pliocene sediments of the hominin-bearing Hadar Formation. Tephra deposits of the Bouroukie Tuff 2 volcanic complex (BKT-2) are important regional markers, and here we provide correlations between the Hadar and Ledi-Geraru project areas using major-element glass chemistry, stratigraphic relationships, outcrop characteristics, and 40Ar/39Ar dates. These correlations greatly expand existing temporal and spatial resolution, aid in interpretations of regional depositional environments, and increase the documented extent of BKT-2 to ∼600 km2. BKT-2 exposures at Ledi-Geraru are the thickest and most complete yet observed. There, the BKT-2 complex is preserved as two air-fall lapilli layers, BKT-2U (<97 cm thick) and BKT-2L (<9 cm thick), separated by <2.5 m of silts and clays or diatomite that overlie the Green Marker Bed (GMB), a laminated ash tuff. Measured sections were evaluated to create a stratigraphy-based model of paleolandscape variations using BKT-2 tephra as laterally extensive isochronous surfaces. BKT-2 was mainly erupted into lacustrine and nearshore environments. The eastern Ledi-Geraru region was likely located at the depocenter of an expansive fluviolacustrine network. Representing the last major lacustrine phase of the Hadar Formation, lateral facies variations show the westward expansion of a lacustrine setting ca. 2.96 Ma followed by eastward regression initiated sometime prior to the eruption of BKT-2U ca. 2.94 Ma. High-resolution, well-correlated, and temporally constrained stratigraphic records are key to the interpretation of paleoenvironmental variation in East Africa.",
keywords = "Afar Depression, Hadar Formation, Paleoenvironment, Pliocene, Tephrochronology, Tephrostratigraphy",
author = "DiMaggio, {Erin N.} and Christopher Campisano and Ramon Arrowsmith and Kaye Reed and Swisher, {Carl C.} and Lockwood, {Charles A.}",
year = "2008",
doi = "10.1130/2008.2446(07)",
language = "English (US)",
volume = "446",
pages = "163--177",
journal = "Special Paper of the Geological Society of America",
issn = "0072-1077",
publisher = "Geological Society of America",

}

TY - JOUR

T1 - Correlation and stratigraphy of the BKT-2 volcanic complex in west-central Afar, Ethiopia

AU - DiMaggio, Erin N.

AU - Campisano, Christopher

AU - Arrowsmith, Ramon

AU - Reed, Kaye

AU - Swisher, Carl C.

AU - Lockwood, Charles A.

PY - 2008

Y1 - 2008

N2 - Located adjacent to the paleoanthropological site of Hadar in Afar, Ethiopia, the Ledi-Geraru project area preserves multiple tephra deposits within the Pliocene sediments of the hominin-bearing Hadar Formation. Tephra deposits of the Bouroukie Tuff 2 volcanic complex (BKT-2) are important regional markers, and here we provide correlations between the Hadar and Ledi-Geraru project areas using major-element glass chemistry, stratigraphic relationships, outcrop characteristics, and 40Ar/39Ar dates. These correlations greatly expand existing temporal and spatial resolution, aid in interpretations of regional depositional environments, and increase the documented extent of BKT-2 to ∼600 km2. BKT-2 exposures at Ledi-Geraru are the thickest and most complete yet observed. There, the BKT-2 complex is preserved as two air-fall lapilli layers, BKT-2U (<97 cm thick) and BKT-2L (<9 cm thick), separated by <2.5 m of silts and clays or diatomite that overlie the Green Marker Bed (GMB), a laminated ash tuff. Measured sections were evaluated to create a stratigraphy-based model of paleolandscape variations using BKT-2 tephra as laterally extensive isochronous surfaces. BKT-2 was mainly erupted into lacustrine and nearshore environments. The eastern Ledi-Geraru region was likely located at the depocenter of an expansive fluviolacustrine network. Representing the last major lacustrine phase of the Hadar Formation, lateral facies variations show the westward expansion of a lacustrine setting ca. 2.96 Ma followed by eastward regression initiated sometime prior to the eruption of BKT-2U ca. 2.94 Ma. High-resolution, well-correlated, and temporally constrained stratigraphic records are key to the interpretation of paleoenvironmental variation in East Africa.

AB - Located adjacent to the paleoanthropological site of Hadar in Afar, Ethiopia, the Ledi-Geraru project area preserves multiple tephra deposits within the Pliocene sediments of the hominin-bearing Hadar Formation. Tephra deposits of the Bouroukie Tuff 2 volcanic complex (BKT-2) are important regional markers, and here we provide correlations between the Hadar and Ledi-Geraru project areas using major-element glass chemistry, stratigraphic relationships, outcrop characteristics, and 40Ar/39Ar dates. These correlations greatly expand existing temporal and spatial resolution, aid in interpretations of regional depositional environments, and increase the documented extent of BKT-2 to ∼600 km2. BKT-2 exposures at Ledi-Geraru are the thickest and most complete yet observed. There, the BKT-2 complex is preserved as two air-fall lapilli layers, BKT-2U (<97 cm thick) and BKT-2L (<9 cm thick), separated by <2.5 m of silts and clays or diatomite that overlie the Green Marker Bed (GMB), a laminated ash tuff. Measured sections were evaluated to create a stratigraphy-based model of paleolandscape variations using BKT-2 tephra as laterally extensive isochronous surfaces. BKT-2 was mainly erupted into lacustrine and nearshore environments. The eastern Ledi-Geraru region was likely located at the depocenter of an expansive fluviolacustrine network. Representing the last major lacustrine phase of the Hadar Formation, lateral facies variations show the westward expansion of a lacustrine setting ca. 2.96 Ma followed by eastward regression initiated sometime prior to the eruption of BKT-2U ca. 2.94 Ma. High-resolution, well-correlated, and temporally constrained stratigraphic records are key to the interpretation of paleoenvironmental variation in East Africa.

KW - Afar Depression

KW - Hadar Formation

KW - Paleoenvironment

KW - Pliocene

KW - Tephrochronology

KW - Tephrostratigraphy

UR - http://www.scopus.com/inward/record.url?scp=75449092000&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=75449092000&partnerID=8YFLogxK

U2 - 10.1130/2008.2446(07)

DO - 10.1130/2008.2446(07)

M3 - Article

AN - SCOPUS:75449092000

VL - 446

SP - 163

EP - 177

JO - Special Paper of the Geological Society of America

JF - Special Paper of the Geological Society of America

SN - 0072-1077

ER -