Detrital zircon double-dating of forearc basin strata reveals magmatic, exhumational, and thermal history of sediment source areas

Enkelmann, Eva; Lohff, Sonia K. Sanchez; Finzel, Emily S.

doi:10.1130/b35043.1

Cited by 14 publications

(12 citation statements)

References 66 publications

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“…By combining zircon FT and U‐Pb data on individual grains (double‐dating), we can better constrain the grain provenance as well as categorize the grains ZFT age as recording either magmatic cooling or exhumational cooling (Enkelmann et al, ). We consider grains yielding the same ZFT and U‐Pb ages within analytical error (1σ) to be magmatically cooled, representing extrusive and shallow intrusive source rocks.…”

Section: Resultsmentioning

confidence: 99%

Late Miocene to Pleistocene Source to Sink Record of Exhumation and Sediment Routing in the Gulf of Alaska From Detrital Zircon Fission‐Track and U‐Pb Double Dating

2019

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We investigate the late Miocene‐Pleistocene offshore sedimentary record of the Yakutat microplate to evaluate the spatial and temporal variations in rock exhumation and sediment routing patterns at the heavily glaciated and actively converging plate boundary in southeast Alaska. We present 1,456 new fission track ages and 1,372 new U‐Pb ages from double‐dated detrital zircons derived from fourteen samples collected from offshore. We integrate our results with published geochronology and thermochronology data onland and offshore in order to constrain grain provenance. We find that offshore strata deposited east of the fold and thrust belt are sourced from the rapidly exhuming areas along the entire Fairweather Fault, the northeastern part of the syntaxial region, as well as the slowly exhuming Insular superterrane. In contrast, the western strata are sourced from the emerging fold and thrust belt and the Chugach Metamorphic Complex located north of the plate boundary. In these samples we identified a change in sediment provenance, which we suggest marks the capture of the Bagley Ice Valley by the proto‐Bering Glacier at the transition from the early to late Pliocene. This implies that the modern Bagley‐Bering Glacier System is much older than previously known. Strata deposited at ~8.6 Ma suggest that extreme rapid exhumation was already ongoing in the late Miocene, which supports previous findings in deep‐sea deposits. Overall, the data help discern several stages in the evolution of sediment routing patterns in response to dynamic tectonic and surficial processes along this active convergent margin.

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Section: Resultsmentioning

confidence: 99%

Late Miocene to Pleistocene Source to Sink Record of Exhumation and Sediment Routing in the Gulf of Alaska From Detrital Zircon Fission‐Track and U‐Pb Double Dating

2019

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“…35-30 Ma) and continued into early-middle Miocene time (ca. 16-11 Ma; Little and Naeser, 1989;Hoffman and Armstrong, 2006;Arkle et al, 2013;Enkelmann et al, 2019). Exhumation of this region is inferred to reflect initial insertion of the shallow Yakutat slab (Enkelmann et al, 2008(Enkelmann et al, , 2010Finzel et al, 2011Finzel et al, , 2015Arkle et al, 2013).…”

Section: Oligocenementioning

confidence: 96%

“…Upper Cretaceous strata record the addition of a new source region in the Chugach Mountains, and to a much lesser extent, the eastern Alaska Range and Yukon-Tanana Uplands (Figure 11). A prominent 98 Ma zircon fission track peak from modern rivers draining the Talkeetna Mountains reveals ongoing exhumation in that region (Enkelmann et al, 2019). Late Cretaceous exhumation of the accretionary prism could be related to changes in plate kinematics induced by final suturing of the Insular terranes.…”

Section: Forearc Basin Response To External Tectonic Forcingmentioning

confidence: 99%

“…Previous qualitative assessment of detrital zircon U-Pb distributions and εHf (t) values in Lower-Middle Miocene strata suggest that sediment was derived from all margins of the basin, including the central and eastern Alaska Range, western Talkeetna Mountains, and northern Chugach Mountains (Finzel and Enkelmann, 2017). Some of those regions, including the central Alaska Range, western Alaska Range, and eastern Alaska Range produce detrital zircon and apatite fission track ages that reflect late Oligocene to early Miocene (∼30-18 Ma) initial and widespread exhumation (Lease et al, 2016;Enkelmann et al, 2019). In addition, apatite thermochronologic ages <20 Ma in the western Chugach Mountains and Talkeetna Mountains indicate exhumation during the Miocene (Little and Naeser, 1989;Hoffman and Armstrong, 2006;Arkle et al, 2013;Valentino et al, 2016).…”

Section: Miocenementioning

confidence: 99%

“…The Yakutat microplate is an ∼11-30 km thick, wedge-shaped oceanic plateau that is subducting at a dip angle of 11-16 • , decreasing from west to east, to near the modern coastline (Ferris et al, 2003;Eberhart-Phillips et al, 2006;Worthington et al, 2008Worthington et al, , 2012Christeson et al, 2010;Bauer et al, 2014). Yakutat shallow-subduction-related processes observed in the upper plate in Alaska include changes in (1) the style and location of volcanic arc magmatism, (2) sedimentary basin subsidence and inversion patterns, and (3) sediment sources as a result of accelerated surface uplift above the subducted flat slab (e.g., Enkelmann et al, 2008Enkelmann et al, , 2019Finzel et al, 2011Finzel et al, , 2015Finzel et al, , 2016Trop et al, 2012;Arkle et al, 2013;Finzel and Enkelmann, 2017). Shallow subduction still characterizes the present-day margin of southern Alaska.…”

Section: Existing Provenance and Tectonic Modelsmentioning

confidence: 99%

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