Mantle and geological evidence for a Late Jurassic−Cretaceous suture spanning North America

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Full frame distilled prediction

Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.

Candidate categories

Insufficient payload (model declined to judge)

Consensus categories

none

Domain

Candidate signal: noneConsensus signal: none

Study design

Candidate signal: ObservationalConsensus signal: Observational

Genre

Candidate signal: EmpiricalConsensus signal: Empirical

Teacher disagreement score

0.092

Threshold uncertainty score

0.993

Validation status

machine_predicted_unvalidated · codex-gemma-dda1882f352a

Codex and Gemma teacher scores by category

Machine scores (provisional)

The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.

Teacher spread

0.211 · how far apart the two teachers sit on this one work

Validation status

score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it

Abstract

<p xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:etd="http://www.ndltd.org/standards/metadata/etdms/1.0" xmlns:ora="http://ora.ox.ac.uk/ora" xmlns:xs="http://www.w3.org/2001/XMLSchema">Crustal blocks accreted to North America form two major belts which are separated by a tract of collapsed Jura-Cretaceous basins extending from Alaska to Mexico. Evidence of oceanic lithosphere that once underlay these basins is rare at the earth’s surface. Most of the lithosphere was subducted, which accounts for the general difficulty of reconstructing oceanic regions from surface evidence. However, this seafloor was not destroyed; it remains in the mantle beneath North America and is visible to seismic tomography, revealing configurations of arc-trench positions back to the breakup of Pangea. The double uncertainty of where trenches ran and how subducting lithosphere deformed while sinking in the mantle is surmountable, owing to the presence of a special-case slab geometry. Wall-like, linear slab belts exceeding 10,000 km in length appear to trace out intra-oceanic subduction zones that were stationary over tens of millions of years, and beneath which lithosphere sank almost vertically. This hypothesis sets up an absolute lower-mantle reference frame. Combined with a complete Atlantic spreading record that paleo-positions North America in this reference frame, the slab geometries permit detailed predictions of where and when ocean basins at the leading edge of westward-drifting North America were subducted, how intra-oceanic subduction zones were overridden, and how their associated arcs and basement terranes were sutured to the continent. An unconventional paleogeography is predicted in which mid- to late Mesozoic arcs grew in a long-lived archipelago located 2000-4000 km west of Pangean North America (while also consistent with the conventional view of a continental arc in early Mesozoic times). The Farallon Ocean subducted beneath the outboard (western) edge of the archipelago, whereas North America converged on the archipelago by westward subduction of an intervening, major ocean, the Mezcalera-Angayucham Oceans.</p> <p xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:etd="http://www.ndltd.org/standards/metadata/etdms/1.0" xmlns:ora="http://ora.ox.ac.uk/ora" xmlns:xs="http://www.w3.org/2001/XMLSchema">The most conspicuous geologic prediction is that of an oceanic suture which must run along the entire western margin of North America. It formed diachronously between ~155 Ma and ~50 Ma, analogous to diachronous suturing of southwest Pacific arcs to the northward migrating Australian continent today. We proceed to demonstrate that this suture prediction fits the spatiotemporal evidence for the collapse of at least 11 Middle Jurassic to Late Cretaceous basins wedged between the Intermontane and Insular-Guerrero superterranes, about half of which are known to contain mantle rocks. These relative late suturing ages run counter to the Middle Jurassic or older timing required and asserted by the prevailing, Andean-analogue model for the North American Cordillera. We show that the arguments against late suturing are controvertible, and we present multiple lines of direct evidence for late suturing, consistent with geophysical observations. We refer to our close integration of surface and subsurface evidence from geology and geophysics as “tomotectonic analysis”. It provides a stringent test for currently accepted tectonic models and offers a blueprint for similar, continental-scale investigations in other accretionary orogens.</p>

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The record

Venue

Geological Society of America Bulletin

Topic

Geological and Geochemical Analysis

Field

Earth and Planetary Sciences

Canadian institutions

Geological Survey of Canada

Funders

not available

Keywords

GeologySubductionLithosphereNorth American PlateMantle (geology)Seafloor spreadingPaleontologyCretaceousTerranePacific PlateTectonics

Has abstract in OpenAlex

yes

API

/api/v1/works/W2755284352