Ridge-trench interactions and the Neogene tectonic evolution of the Magdalena shelf and southern Gulf of California

Insights from detrital zircon U-Pb ages from the Magdalena fan and adjacent areas

John M. Fletcher, Marty Grove, David Kimbrough, Oscar Lovera, George E Gehrels

Research output: Contribution to journalArticle

100 Citations (Scopus)

Abstract

The Magdalena fan is an apparently beheaded submarine depocenter that has figured prominently in reconstructions of middle to late Miocene Pacific-North American plate interactions. The deposit accumulated rapidly at the base of the continental slope on top of newly formed oceanic crust of the Magdalena microplate from 14.5 to 13 Ma. Subduction of this crust ceased as the Pacific-Magdalena spreading center encountered the trench. The widely accepted two-phase kinematic model for the formation of the Gulf of California holds that ∼300 km of dextral shear between the Pacific and North American plates occurred along faults west of Baja California prior to the onset of dextral-transtensional shearing in the gulf ca. 6 Ma. We measured 1796 detrital zircon U-Pb ages from 65 samples in an effort to characterize the provenance of the fan, determine its source region, and define the cumulative dextral slip along faults offshore of southwestern Baja California. Zircons from the fan are dominantly 120-65 Ma with subordinate 15-35 Ma grains. Excellent matches to the fan can be obtained by mixing Magdalena shelf strata and/or adding detritus from the west-draining portion of the Los Cabos block. The same cannot be accomplished with zircons from the east-draining portion of the Los Cabos block and mainland Mexico. Our results favor a western Baja source region for the fan and suggest that cumulative dextral slip along faults west of Baja was <150 km, much less than previously believed. We propose that the fan was fed by erosional denudation of the Magdalena shelf produced by increased mantle buoyancy due to the ridge-trench juxtaposition. The fan's source was cut off when faults west of Baja California began to accommodate transtensional shearing and form rift basins that captured detritus that previously reached the trench.

Original languageEnglish (US)
Pages (from-to)1313-1336
Number of pages24
JournalBulletin of the Geological Society of America
Volume119
Issue number11-12
DOIs
StatePublished - Nov 2007

Fingerprint

tectonic evolution
Neogene
trench
zircon
North American plate
detritus
depocenter
microplate
spreading center
denudation
continental slope
oceanic crust
buoyancy
provenance
subduction
kinematics
Miocene
crust
mantle
gulf

Keywords

  • Baja California
  • Detrital zircon
  • Gulf of California
  • Integrated Ocean Drilling Program
  • Magdalena fan
  • Mexico
  • Neogene
  • U-Pb

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

@article{c8390005c8304d82b5de259bf4c7af18,
title = "Ridge-trench interactions and the Neogene tectonic evolution of the Magdalena shelf and southern Gulf of California: Insights from detrital zircon U-Pb ages from the Magdalena fan and adjacent areas",
abstract = "The Magdalena fan is an apparently beheaded submarine depocenter that has figured prominently in reconstructions of middle to late Miocene Pacific-North American plate interactions. The deposit accumulated rapidly at the base of the continental slope on top of newly formed oceanic crust of the Magdalena microplate from 14.5 to 13 Ma. Subduction of this crust ceased as the Pacific-Magdalena spreading center encountered the trench. The widely accepted two-phase kinematic model for the formation of the Gulf of California holds that ∼300 km of dextral shear between the Pacific and North American plates occurred along faults west of Baja California prior to the onset of dextral-transtensional shearing in the gulf ca. 6 Ma. We measured 1796 detrital zircon U-Pb ages from 65 samples in an effort to characterize the provenance of the fan, determine its source region, and define the cumulative dextral slip along faults offshore of southwestern Baja California. Zircons from the fan are dominantly 120-65 Ma with subordinate 15-35 Ma grains. Excellent matches to the fan can be obtained by mixing Magdalena shelf strata and/or adding detritus from the west-draining portion of the Los Cabos block. The same cannot be accomplished with zircons from the east-draining portion of the Los Cabos block and mainland Mexico. Our results favor a western Baja source region for the fan and suggest that cumulative dextral slip along faults west of Baja was <150 km, much less than previously believed. We propose that the fan was fed by erosional denudation of the Magdalena shelf produced by increased mantle buoyancy due to the ridge-trench juxtaposition. The fan's source was cut off when faults west of Baja California began to accommodate transtensional shearing and form rift basins that captured detritus that previously reached the trench.",
keywords = "Baja California, Detrital zircon, Gulf of California, Integrated Ocean Drilling Program, Magdalena fan, Mexico, Neogene, U-Pb",
author = "Fletcher, {John M.} and Marty Grove and David Kimbrough and Oscar Lovera and Gehrels, {George E}",
year = "2007",
month = "11",
doi = "10.1130/B26067.1",
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volume = "119",
pages = "1313--1336",
journal = "Geological Society of America Bulletin",
issn = "0016-7606",
publisher = "Geological Society of America",
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TY - JOUR

T1 - Ridge-trench interactions and the Neogene tectonic evolution of the Magdalena shelf and southern Gulf of California

T2 - Insights from detrital zircon U-Pb ages from the Magdalena fan and adjacent areas

AU - Fletcher, John M.

AU - Grove, Marty

AU - Kimbrough, David

AU - Lovera, Oscar

AU - Gehrels, George E

PY - 2007/11

Y1 - 2007/11

N2 - The Magdalena fan is an apparently beheaded submarine depocenter that has figured prominently in reconstructions of middle to late Miocene Pacific-North American plate interactions. The deposit accumulated rapidly at the base of the continental slope on top of newly formed oceanic crust of the Magdalena microplate from 14.5 to 13 Ma. Subduction of this crust ceased as the Pacific-Magdalena spreading center encountered the trench. The widely accepted two-phase kinematic model for the formation of the Gulf of California holds that ∼300 km of dextral shear between the Pacific and North American plates occurred along faults west of Baja California prior to the onset of dextral-transtensional shearing in the gulf ca. 6 Ma. We measured 1796 detrital zircon U-Pb ages from 65 samples in an effort to characterize the provenance of the fan, determine its source region, and define the cumulative dextral slip along faults offshore of southwestern Baja California. Zircons from the fan are dominantly 120-65 Ma with subordinate 15-35 Ma grains. Excellent matches to the fan can be obtained by mixing Magdalena shelf strata and/or adding detritus from the west-draining portion of the Los Cabos block. The same cannot be accomplished with zircons from the east-draining portion of the Los Cabos block and mainland Mexico. Our results favor a western Baja source region for the fan and suggest that cumulative dextral slip along faults west of Baja was <150 km, much less than previously believed. We propose that the fan was fed by erosional denudation of the Magdalena shelf produced by increased mantle buoyancy due to the ridge-trench juxtaposition. The fan's source was cut off when faults west of Baja California began to accommodate transtensional shearing and form rift basins that captured detritus that previously reached the trench.

AB - The Magdalena fan is an apparently beheaded submarine depocenter that has figured prominently in reconstructions of middle to late Miocene Pacific-North American plate interactions. The deposit accumulated rapidly at the base of the continental slope on top of newly formed oceanic crust of the Magdalena microplate from 14.5 to 13 Ma. Subduction of this crust ceased as the Pacific-Magdalena spreading center encountered the trench. The widely accepted two-phase kinematic model for the formation of the Gulf of California holds that ∼300 km of dextral shear between the Pacific and North American plates occurred along faults west of Baja California prior to the onset of dextral-transtensional shearing in the gulf ca. 6 Ma. We measured 1796 detrital zircon U-Pb ages from 65 samples in an effort to characterize the provenance of the fan, determine its source region, and define the cumulative dextral slip along faults offshore of southwestern Baja California. Zircons from the fan are dominantly 120-65 Ma with subordinate 15-35 Ma grains. Excellent matches to the fan can be obtained by mixing Magdalena shelf strata and/or adding detritus from the west-draining portion of the Los Cabos block. The same cannot be accomplished with zircons from the east-draining portion of the Los Cabos block and mainland Mexico. Our results favor a western Baja source region for the fan and suggest that cumulative dextral slip along faults west of Baja was <150 km, much less than previously believed. We propose that the fan was fed by erosional denudation of the Magdalena shelf produced by increased mantle buoyancy due to the ridge-trench juxtaposition. The fan's source was cut off when faults west of Baja California began to accommodate transtensional shearing and form rift basins that captured detritus that previously reached the trench.

KW - Baja California

KW - Detrital zircon

KW - Gulf of California

KW - Integrated Ocean Drilling Program

KW - Magdalena fan

KW - Mexico

KW - Neogene

KW - U-Pb

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DO - 10.1130/B26067.1

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