This paper synthesizes the framework and geological evolution of the Arctic Alaska–Chukotka microplate (AACM), from its origin as part of the continental platform fringing Baltica and Laurentia to its southward motion during the formation of the Amerasia Basin (Arctic Ocean) and its progressive modification as part of the dynamic northern palaeo-Pacific margin. A synthesis of the available data refines the crustal identity, limits and history of the AACM and, together with regional geological constraints, provides a tectonic framework to aid in its pre-Cretaceous restoration. Recently published seismic reflection data and interpretations, integrated with regional geological constraints, provide the basis for a new crustal transect (the Circum-Arctic Lithosphere Evolution (‘CALE’) Transect C) linking the Amerasia Basin and the Pacific margin along two paths that span 5100 km from the Lomonosov Ridge (near the North Pole), across the Amerasia Basin, Chukchi Sea and Bering Sea, and ending at the subducting Pacific plate margin in the Aleutian Islands. We propose a new plate tectonic model in which the AACM originated as part of a re-entrant in the palaeo-Pacific margin and moved to its present position during slab-related magmatism and the southward retreat of palaeo-Pacific subduction, largely coeval with the rifting and formation of the Amerasia Basin in its wake.

Submarine volcanism in the western Arctic Ocean, known as Amerasia Basin, is attributed to a mantle plume based on geophysics and meager geochemical evidence. Basaltic samples dredged from Chukchi Borderland within the basin have produced minimum 40Ar/39Ar ages for eruption at circa 118–112, circa 105–100, and circa 90–70 Ma, which we use to constrain tectonic models for basin opening. Major oxide and trace element concentrations and Sr, Nd, and Hf isotopic ratios of the lavas show that the circa 118–112 Ma samples from Northwind Ridge are tholeiites (low‐Ti tholeiite I) with low degrees of rare‐earth element (REE) fractionation, high overall heavy rare‐earth element (HREE), and Mg# (Mg‐number), which suggests magma derivation from a garnet‐free source followed by minor crystal fractionation. Strontium, Nd, and Hf isotope systematics for these lavas and ratios of highly incompatible trace elements point toward a lithospheric source. Eruptions at circa 105–100 and circa 90–70 Ma, both at Healy Spur, produced two types of lavas: low‐Ti tholeiite II—which are generally older than high‐Ti tholeiite—both common in continental flood basalt (CFB) provinces and both with trace element abundance patterns typifying a garnet‐free source and significant crystal fractionation for the high‐Ti tholeiite. The isotope characteristics for both groups are common features of asthenospheric sources. Composition‐time relationships for the lavas suggest inception of melting in the subcontinental lithospheric mantle (SCLM)—probably due to introduction of a heat source by a plume—followed later (at ca. 105–100 and ca. 90–70 Ma) by asthenospheric melting possibly triggered by plume rise.

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The history of the deep Arctic Ocean is largely unwritten. The means to understand this history may now be at hand. Bathymetry and potential field data have accumulated to the point it is possible to ask specific questions about the origins and evolution of the individual ridges and basins. The two primary basins have contrasting histories and deficits of understanding. The Eurasia Basin, formed during the Cenozoic, is well understood as far as the kinematics are concerned. The dynamics of ultraslow spreading, as observed on the Gakkel Ridge, are not well understood. It is widely thought that the Amerasia Basin formed during the Mesozoic. Most previous work has begun with a large-scale model of the basin tectonics and fit the ridges and basins it into this pattern. Enough is now known to establish the internal structure and relations from specific observations rather than a priori assumptions. This paper reviews knowledge about the central Arctic Ocean and proposes what should be done to develop a historical understanding of basin history. Ground truth from Arctic Ocean sediments is necessary. It will not be possible to establish the history of events, in geological time, until the sediments have been sampled and dated.