Evolution of the Pacific Margin: Progress and Future

Evolution of the Pacific Margin: Evolution of the Pacific Margin: Progress and FutureProgress and Future

Jeremy Hourigan, Yale UniversityJeremy Hourigan, Yale UniversitySergei D. Sokolov, GIN-RAS MoscowSergei D. Sokolov, GIN-RAS MoscowAleksandr I. Khanchuk, FEGI-RAS, Aleksandr I. Khanchuk, FEGI-RAS,

VladivostokVladivostok

Outline of ProgressOutline of Progress

Pre-Late Cretaceous Pacific Convergent MarginPre-Late Cretaceous Pacific Convergent Margin Sea of OkhotskSea of Okhotsk Olyutorsky Arc-Collision zone, Kamchatka Olyutorsky Arc-Collision zone, Kamchatka Neotectonics - Neotectonics - upper crustal response to plate

margin processes Geophysics - Geophysics - structure of the modern subduction

zone

Terrane Map:Terrane Map: Nokleberg et

al, 1998

Major collaborative effort to compile geology of NE Russian

Widely accessible database

Progress: Pre-Late Cretaceous Progress: Pre-Late Cretaceous Convergent Margin evolutionConvergent Margin evolution

Laboratory of Tectonics of Oceanic Laboratory of Tectonics of Oceanic and Perioceanic zones (Sokolov)and Perioceanic zones (Sokolov)• Pekul’ney RangePekul’ney Range• Koryak HighlandsKoryak Highlands• Taigonos PeninsulaTaigonos Peninsula

Transform-margin evolution in Transform-margin evolution in Primoriye (Khanchuk)Primoriye (Khanchuk)

Outline of ProgressOutline of Progress

Uda-Murgal Arc evolution Uda-Murgal Arc evolution • Improved understanding of Pacific plate Improved understanding of Pacific plate

geometry and kinematics from the geometry and kinematics from the record far-traveled material in record far-traveled material in accretionary prism (geochemistry, accretionary prism (geochemistry, radiolarian stratigraphy, and radiolarian stratigraphy, and paleomagnetic)paleomagnetic)

• Tectonic reconstruction of Pre-mid Tectonic reconstruction of Pre-mid Cretaceous NE Russian MarginCretaceous NE Russian Margin

Modern extent of the Uda-Murgal Modern extent of the Uda-Murgal ArcArc

Late Jurassic –Early Cretaceous Margin

•Alaska-Aleutian or Kamchatka-Kurile margin analog•Continental arc grades offshore to island arc

Pekul’ney SegmentPekul’ney Segment

Island arc separated by back arc basin

Penzhina Segment Penzhina Segment

Island arc built on continental crust

Taigonos SegmentTaigonos Segment

Island arc built on continental crust

Major contribution understanding character of subducting plate(s) via multidisciplinary analysis of accreted material

Cape Povorotniy Cape Povorotniy Accretionary ComplexAccretionary Complex

•Basalt-chert associations•Island Arc Volcanic unit•Melange unit

Accreted Complexes are:Accreted Complexes are:A record (relict fragments) of plate(s) of the Pacific that are interacting with the Asian continental margin.

These fragments carry rich These fragments carry rich information regarding:information regarding:

1)Pacific paleogeography (biostratigraphy)

2)Plate boundaries (convergent, divergent)

3)Terrane transport magnitude (paleomagnetism, radiolarian stratigraphy)

Data on the origin and transport Data on the origin and transport history of accreted material history of accreted material complemented by studies within the complemented by studies within the magmatic belt (geochronologic, magmatic belt (geochronologic, geochemical and structural) provide geochemical and structural) provide a better understanding of NE Russian a better understanding of NE Russian arc systemsarc systems

28.0 ± 3.5 ºN

34.4 ± 4.3 ºN

Extension of transform margins takes about 8% of the Extension of transform margins takes about 8% of the total length of the current continental margins that total length of the current continental margins that makes this type of plate boundaries important. makes this type of plate boundaries important. However, all the geodynamic reconstructions that However, all the geodynamic reconstructions that have been published until presently use the have been published until presently use the subduction model for all the boundaries between subduction model for all the boundaries between oceanic and continental plates, even those made for oceanic and continental plates, even those made for the areas where shifting of an oceanic plate at the the areas where shifting of an oceanic plate at the sharp angle or parallel to an adjacent continental sharp angle or parallel to an adjacent continental margin is suggested. This is obviously due to the lack margin is suggested. This is obviously due to the lack of criteria for distinguishing a transform-margin of criteria for distinguishing a transform-margin setting among others occurred during the geological setting among others occurred during the geological history.history.

Our study of the Mesozoic and Cenozoic Our study of the Mesozoic and Cenozoic tectonic structures and rock complexes in the tectonic structures and rock complexes in the Northwest Pacific Rim that took into account Northwest Pacific Rim that took into account the California-type margin allowed us to the California-type margin allowed us to establish the following indications of the establish the following indications of the transform-margin regime:transform-margin regime:

1.1. Strike-slip faulting along the plate boundaries Strike-slip faulting along the plate boundaries occurring in the time interval under consideration.occurring in the time interval under consideration.

2.2. Formation of basins with avalanche-type Formation of basins with avalanche-type sedimentation of arkosic turbidites along plate sedimentation of arkosic turbidites along plate boundary. This turbidite is distinguished from those boundary. This turbidite is distinguished from those of passive continental margins by that the of passive continental margins by that the subductionary rock complexes laterally replace subductionary rock complexes laterally replace them. Well-known strike-slip basins filled with them. Well-known strike-slip basins filled with terrigenous deposits associated with volcanics are terrigenous deposits associated with volcanics are characteristic of the continental parts of transform characteristic of the continental parts of transform margins. margins.

3.3. Volcanic rocks associated with the strike-slip basins Volcanic rocks associated with the strike-slip basins are distributed very irregularly and combine are distributed very irregularly and combine geochemical characteristics of the subductionary, geochemical characteristics of the subductionary, intraplate and, where and when a spreading center intraplate and, where and when a spreading center submerges beneath the transform margin, MORB submerges beneath the transform margin, MORB sources.sources.  

Okhotsk-Chukotka Volcanic BeltOkhotsk-Chukotka Volcanic Belt

Okhotsk Chukotka Volcanic BeltOkhotsk Chukotka Volcanic Belt

Outline of ProgressOutline of Progress

Sea of Okhotsk Sea of Okhotsk • Sredinniy Range (eastern edge of Sredinniy Range (eastern edge of

Okhotsk Sea microplate?)Okhotsk Sea microplate?)• Seasat gravity datasetSeasat gravity dataset• Analog modeling asymmetric back arc Analog modeling asymmetric back arc

extensionextension• S-wave tomography of sub-Okhotsk S-wave tomography of sub-Okhotsk

mantlemantle• Thermochronologic constraints for Thermochronologic constraints for

extension in the Magadan Basinextension in the Magadan Basin

Recent Analog ModelsRecent Analog Models

Back arc extension recognized as a importantprocess for decades….

Asymmetric back-arc spreading modelSchellart et al. (2003)

Existing models for the origin of the Existing models for the origin of the Okhotsk Sea BasementOkhotsk Sea Basement

Okhotomorsk Oceanic Plateau

Bogdanov and Dobretsov, 2002Parfenov and Natalin, 1977

Structure of the Exterior OCVBStructure of the Exterior OCVB

So flat it’ll drive you to drink

• Dips of rhyolite and basalt units generally less than 5 degrees

•Volcanic section preserved in its entirety – only minor fluvial incision

Reconstruction of the Late Reconstruction of the Late Cretaceous – Early Tertiary marginCretaceous – Early Tertiary margin

Surface Wave Diffraction TomographySurface Wave Diffraction Tomography•Prominent back-arc low-velocity anomaly typical of all back-arc in the western Pacific

•Thermal age of the mantle can be calculated (based on T-dependence of mantle velocity and age dependence of Temp.)

•Thermal age of the mantle beneath the Sea of Okhotsk is Eocene to Miocene

Outline of ProgressOutline of Progress

Olyutorsky arc-continent collision Olyutorsky arc-continent collision zonezone• New timing constraints for arc-continent New timing constraints for arc-continent

collision (Soloviev, Garver and Brandon)collision (Soloviev, Garver and Brandon)• High-grade roots of the Collision zone in High-grade roots of the Collision zone in

the Sredinniy Range the Sredinniy Range

Arc-continent collision Arc-continent collision between Late K – between Late K – Paleocene Paleocene Olyutorsky Olyutorsky ArcArc and the northeast and the northeast Russian continental Russian continental marginmargin

Timing constrained by Timing constrained by fission-track grain-age fission-track grain-age stratigraphy and stratigraphy and biostratigraphy from biostratigraphy from marginal sandstone marginal sandstone units in the lower plateunits in the lower plate

Timing estimates: Timing estimates: 55 55 – 45 Ma– 45 Ma

Cross-cutting granite Cross-cutting granite and overlapping Kinkil and overlapping Kinkil volcanic rocks of the volcanic rocks of the West Kamchatka Belt: West Kamchatka Belt: 45 Ma (U/Pb zircon 45 Ma (U/Pb zircon TIMS, Garver, 2001)TIMS, Garver, 2001)

Comparative evolution of theComparative evolution of theLesnovsk Highlands and Sredinniy Range:Lesnovsk Highlands and Sredinniy Range:

……But Sredinniy exposes metamorphic rocks up to granulite facies, But Sredinniy exposes metamorphic rocks up to granulite facies, Lesnaya group is sub greenschist faciesLesnaya group is sub greenschist facies

Lesnovsk Highlands

Late K upper plate sediments (radiolaria, Inoceramus)

Late K – Eocene lower plate sediments(Detrital zircon FT, nanofossil)

Stitching intrusion and overlapping volcanic rocks - 45 ± 1 Ma (U/Pb zircon)

Partially resent AFT insignificant post-collisional exhumation

Comparative evolution of theComparative evolution of theLesnovsk Highlands and Sredinniy Range:Lesnovsk Highlands and Sredinniy Range:

……But Sredinniy exposes metamorphic rocks up to granulite facies, But Sredinniy exposes metamorphic rocks up to granulite facies, Lesnaya group is sub greenschist faciesLesnaya group is sub greenschist facies

Simplified geologic map of the Simplified geologic map of the Sredinniy RangeSredinniy Range

Kolpakova Gneiss: migmatiteKolpakova Gneiss: migmatite

Accumulation of protolithsAccumulation of protoliths

Arc-obduction and burial of the NE Russian marginArc-obduction and burial of the NE Russian margin

Outline of ProgressOutline of Progress

NeotectonicsNeotectonics• Tephrachronologic, marine terrace Tephrachronologic, marine terrace

record of vertical motion along coastal record of vertical motion along coastal Kamchatka (Bourgeois group)Kamchatka (Bourgeois group)

• Accretion history of Cape Terranes Accretion history of Cape Terranes (Mann and co-workers; Gaedicke and (Mann and co-workers; Gaedicke and others)others)

Cenozoic Geodynamic Associations of Kamchatka PeninsulaCenozoic Geodynamic Associations of Kamchatka Peninsula

Cross-section of rapid anomalies along the Kurils-Kamchatka Cross-section of rapid anomalies along the Kurils-Kamchatka subduction zone profile (according to Gordeyev and others.)subduction zone profile (according to Gordeyev and others.)

Paleogeodynamic scheme Paleogeodynamic scheme of the Early Miocene of the Early Miocene

Northwest Pacific Northwest Pacific (magnetic anomaly 6) (magnetic anomaly 6)

(according to Silvestrov, (according to Silvestrov, 1998, with add-ins) 1998, with add-ins)

The Mesozoic-Cenozoic development of the The Mesozoic-Cenozoic development of the Northwest Pacific margins occurred as Northwest Pacific margins occurred as alternation of episodes while either subduction alternation of episodes while either subduction or transform geodynamic regime predominated. or transform geodynamic regime predominated. Predomination of one of the two regimes was Predomination of one of the two regimes was controlled by system of motions between the controlled by system of motions between the plates adjacent to the Eurasian plate, as well as plates adjacent to the Eurasian plate, as well as mutual orientation of the Eurasian plate edges mutual orientation of the Eurasian plate edges at the location studied.at the location studied.

Outline of ProgressOutline of Progress

Geophysics – Modern subduction Geophysics – Modern subduction zone structurezone structure• SEKS experiment (Side-Edge of the SEKS experiment (Side-Edge of the

Kamchatka Slab)Kamchatka Slab)• Crustal Structure of Kamchatka and Crustal Structure of Kamchatka and

Mainland RussiaMainland Russia• Mantle velocity structure beneath the Mantle velocity structure beneath the

Sea of OkhotskSea of Okhotsk

Workshop objectiveWorkshop objective

Establish links between geodetic, Establish links between geodetic, neotectonic, structural, neotectonic, structural, thermochronologic, and geophysical thermochronologic, and geophysical disciplines to understand the disciplines to understand the evolution of the Pacific margin at a evolution of the Pacific margin at a range of time and length scales.range of time and length scales.

Discussion objectivesDiscussion objectives

Establish links between geodetic, Establish links between geodetic, neotectonic, structural, neotectonic, structural, thermochronologic, and geophysical thermochronologic, and geophysical disciplines to understand the disciplines to understand the evolution of the Pacific margin at a evolution of the Pacific margin at a range of time and length scales range of time and length scales cross-disciplinary approach.cross-disciplinary approach.

Discussion objectivesDiscussion objectives The southern continuation The southern continuation Understanding linkages with Understanding linkages with

Mongol-Okhotsk Belt and Sikhote-Alin MarginMongol-Okhotsk Belt and Sikhote-Alin Margin Radiation of angiosperms – climatic and paleobotanical Radiation of angiosperms – climatic and paleobotanical

implications (EARTHTIME Iniative)implications (EARTHTIME Iniative)

The Sea of OkhotskThe Sea of Okhotsk Origin of basementOrigin of basement Time-space patterns of extensional basin formation and Time-space patterns of extensional basin formation and

strike-slip faultingstrike-slip faulting Role of Pacific plate roll-back, strike-slip modification, and Role of Pacific plate roll-back, strike-slip modification, and

Asian extrusion Asian extrusion If the Sea of Okhotsk is a microplate, when did it achieve If the Sea of Okhotsk is a microplate, when did it achieve

the microplate character? the microplate character?

Discussion objectivesDiscussion objectives

KamchatkaKamchatka• Cross disciplinary projects that address Cross disciplinary projects that address

the evolution of the Aleutian Kamchatka the evolution of the Aleutian Kamchatka junctionjunction

• Evolution of high grade metamorphic Evolution of high grade metamorphic rocks in a collage of low-grade accreted rocks in a collage of low-grade accreted terranes (Sredinniy, Ganal and terranes (Sredinniy, Ganal and Khavyven Ranges)Khavyven Ranges)