Late Cenozoic structure and tectonics of the southern Sierra Nevada–San Joaquin Basin transition, California

This paper presents a new synthesis for the late Cenozoic tectonic, paleogeographic, and geomorphologic evolution of the southern Sierra Nevada and adjacent eastern San Joaquin Basin. The southern Sierra Nevada and San Joaquin Basin contrast sharply, with the former constituting high-relief basement exposures and the latter constituting a Neogene marine basin with superposed low-relief uplifts actively forming along its margins. Nevertheless, we show that Neogene basinal conditions extended continuously eastward across much of the southern Sierra Nevada, and that during late Neogene–Quaternary time, the intra-Sierran basinal deposits were uplifted and fluvially reworked into the San Joaquin Basin. Early Neogene normal-sense growth faulting was widespread and instrumental in forming sediment accommodation spaces across the entire basinal system. Upon erosion of the intra-Sierran basinal deposits, structural relief that formed on the basement surface by the growth faults emerged as topographic relief. Such “weathered out” fossil fault scarps control much of the modern southern Sierra landscape. This Neogene high-angle fault system followed major Late Cretaceous basement structures that penetrated the crust and that formed in conjunction with partial loss of the region’s underlying mantle lithosphere. This left the region highly prone to surface faulting, volcanism, and surface uplift and/or subsidence transients during subsequent tectonic regimes. The effects of the early Neogene passage of the Mendocino Triple Junction were amplified as a result of the disrupted state of the region’s basement. This entailed widespread high-angle normal faulting, convecting mantle-sourced volcanism, and epeirogenic transients that were instrumental in sediment dispersal, deposition, and reworking patterns. Subsequent phases of epeirogenic deformation forced additional sediment reworking episodes across the southern Sierra Nevada–eastern San Joaquin Basin region during the late Miocene break-off and west tilt of the Sierra Nevada microplate and the Pliocene–Quaternary loss of the region’s residual mantle lithosphere that was left intact from the Late Cretaceous tectonic regime. These late Cenozoic events have left the high local-relief southern Sierra basement denuded of its Neogene basinal cover and emergent immediately adjacent to the eastern San Joaquin Basin and its eastern marginal uplift zone

Tectonic control on southern Sierra Nevada topography, California

In this study we integrate the apatite (U-Th)/He thermochronometric technique with geomorphic, structural, and stratigraphic studies to pursue the origin and evolution of topographic relief related to extensive late Cenozoic faulting in the southern Sierra Nevada. The geomorphology of this region reflects a transition from a vast region to the north characterized by nonequilibrium fluvial modification of a relict low-relief landscape, little affected by internal deformation, to a more complex landscape affected by numerous faults. Regionally, the relict landscape surface is readily resolved by age-elevation relationships of apatite He ages coupled to geomorphology. These relationships can be extended into the study area and used as a structural datum for the resolution of fault offsets and related tilting. On the basis of 63 new apatite He ages and stratigraphic data from proximal parts of the San Joaquin basin we resolve two sets of normal faults oriented approximately N–S and approximately NW. Quaternary west-side-up normal faulting along the N–S Breckenridge–Kern Canyon zone has resulted in a southwest step over from the Owens Valley system in the controlling structure on the regional west tilt of Sierran basement. This zone has also served as a transfer structure partitioning Neogene-Quaternary extension resulting from normal displacements on the NW fault set. This fault system for the most part nucleated along Late Cretaceous structures with late Cenozoic remobilization representing passive extension by oblate flattening as the region rose and stretched in response to the passage of a slab window and the ensuing delamination of the mantle lithosphere from beneath the region

Late Cenozoic structure and tectonics of the southern Sierra Nevada–San Joaquin Basin transition, California

This paper presents a new synthesis for the late Cenozoic tectonic, paleogeographic, and geomorphologic evolution of the southern Sierra Nevada and adjacent eastern San Joaquin Basin. The southern Sierra Nevada and San Joaquin Basin contrast sharply, with the former constituting high-relief basement exposures and the latter constituting a Neogene marine basin with superposed low-relief uplifts actively forming along its margins. Nevertheless, we show that Neogene basinal conditions extended continuously eastward across much of the southern Sierra Nevada, and that during late Neogene–Quaternary time, the intra-Sierran basinal deposits were uplifted and fluvially reworked into the San Joaquin Basin. Early Neogene normal-sense growth faulting was widespread and instrumental in forming sediment accommodation spaces across the entire basinal system. Upon erosion of the intra-Sierran basinal deposits, structural relief that formed on the basement surface by the growth faults emerged as topographic relief. Such “weathered out” fossil fault scarps control much of the modern southern Sierra landscape. This Neogene high-angle fault system followed major Late Cretaceous basement structures that penetrated the crust and that formed in conjunction with partial loss of the region’s underlying mantle lithosphere. This left the region highly prone to surface faulting, volcanism, and surface uplift and/or subsidence transients during subsequent tectonic regimes. The effects of the early Neogene passage of the Mendocino Triple Junction were amplified as a result of the disrupted state of the region’s basement. This entailed widespread high-angle normal faulting, convecting mantle-sourced volcanism, and epeirogenic transients that were instrumental in sediment dispersal, deposition, and reworking patterns. Subsequent phases of epeirogenic deformation forced additional sediment reworking episodes across the southern Sierra Nevada–eastern San Joaquin Basin region during the late Miocene break-off and west tilt of the Sierra Nevada microplate and the Pliocene–Quaternary loss of the region’s residual mantle lithosphere that was left intact from the Late Cretaceous tectonic regime. These late Cenozoic events have left the high local-relief southern Sierra basement denuded of its Neogene basinal cover and emergent immediately adjacent to the eastern San Joaquin Basin and its eastern marginal uplift zone

Erosional stripping of the southeastern San Joaquin Basin (SJB) margin off of the southern Sierra Nevada basement uplift

Facies patterns of Neogene strata lying along the intensely faulted southern Sierra Nevada range front indicate that Neogene marine conditions extended for a non-trivial distance across the currently exposed southern Sierra basement. Emergence of the basement is controlled by active W-side-up normal faulting along the Kern Canyon-Breckenridge system, and active NE-side-up normal faulting along the Kern range front-Pond-Poso system. Together these systems produce the regional wedge shaped Breckenridge-Greenhorn horst. The lower slopes of the horst constitute the Kern Arch, a pervasively faulted homocline across which the remnants of the SE SJB Neogene section are undergoing erosion. Neogene basin slope, shelfal, shoreline and paralic facies strata occur continuously along the range front, both faulted against basement and as nonconformable tongues preserved along relay ramps in the fault system. Geologic relations in conjunction with He apatite thermochronometry suggest Neogene growth faulting and transfer motion along the Breckenridge fault, which bounded a system of NW-striking normal faults to the east. Together these faults produced the volcanic (Walker) graben in which the western flank of the 21-16 Ma Cache Peak volcanic center ponded. The southwest corner of the Walker graben was breached by normal faults of the Edison graben that formed a structural trough into the SJB. Currently it is unclear if marine conditions extended all the way into the Walker graben, either through an Edison graben channel, or by overtopping the growing Breckenridge fault. Regional U/Pb zircon basement geochronology and detrital zircon ages from upper Neogene strata, in conjunction with other provenance and stratigraphic data indicate that the Bena Gravel and “Kern River” Formation represent a prograding delta-fluvial plain system that flooded into the SJB, primarily through the Edison graben, as the southern Sierra began regional ascent in the Late Miocene. Continued regional uplift has resulted in the redistribution of most of the Walker graben fill into the SE SJB. In late Pliocene-Quaternary time the Breckenridge-Greenhorn horst began forming with the progressive exhumation of overlying SJB margin strata, and the incision of the lower Kern gorge as a superimposed drainage

Detrital zircon U/Pb ages of upper Miocene to Pleistocene strata of the SE San Joaquin Basin (SJB) in comparison to zircon age patterns of the southern Sierra Nevada Batholith (SNB); implications for late Cenozoic sediment provenance and dispersal patterns

Detrital zircon (dz) ages from upper Cenozoic strata of the SE SJB are compared to a large database on southern SNB zircon ages as a means of better resolving sediment provenance and dispersal patterns as well as the incision history of the lower Kern River basement gorge. Recent stratigraphic and depth of burial studies show that ~ 1500 m of SJB strata sat nonconformably above the low relief basement surface that the lower Kern gorge incised through over the past ~ 1 m.y., calling into question the Kern River as the principal source channel for the Kern River Fm. We focused our studies on the Kern River Fm., and adjacent units such as the Bena and Chanac, which are partly equivalent to the Kern River Fm. These strata all constitute a distinct plutonoclastic lithosome that based on dz data and distinct clasts of Neogene andesite/dacite, was derived from the extreme SE Sierra Nevada. The Neogene clasts were derived from the Cache Peak volcanic center, whose basal ignimbrites contributed distinct ca. 21 Ma volcanic zircon to the SE SNB-dominated dz population. This lithosome was delivered to the SE SJB through a major river trunk that we call the Caliente River, whose terminal channel is clearly expressed in DEMs, issuing westwards into the SJB ~ 10 km south of the lower Kern gorge. The Pleistocene channel walls of the lower Caliente River consist of the same lithosome, which we further trace into the subsurface as the principal lobes of the Stevens submarine fan. The Kern River-Bena-Chanac lithosome represents an upper middle Miocene through Pliocene fluvial-deltaic system that was delivered into the SE SJB through a structural trough that we call the Edison graben. The principal lobes of the Stevens submarine fan formed directly off the delta front. Greater Kern River drainage basement ages and matching dz ages from terrace sands within the lower Kern River are distinct from those of the Caliente lithosome. The Kern drainage dz signal is present in green mudstones and siltstones of latest Miocene-early Pleistocene age, and which replace the Caliente lithosome north of the lower Kern River. These strata are more akin to the Etchegoin and San Joaquin Fms. In parallel, the northern (Rosedale) lobe of the Stevens fan system contains the Kern drainage dz, signaling the deflection of the Kern drainage lithosome by the more voluminous Caliente lithosome

Pliocene cryptic subsidence followed by rapid Quaternary uplift in relation to mantle lithosphere removal, Kern Arch, eastern San Joaquin Basin (SJB), California

The Kern Arch (arch) is an actively growing promontory that extends westwards from the western Sierra Nevada into the eastern SJB where marine strata as young as upper Pliocene are undergoing erosion. Active uplift of the arch is controlled by west-side-up normal faulting along the Kern Canyon-Breckenridge system and northeast-side-up normal faulting along the Kern range front. Quaternary uplift and erosion have resulted in the loss of much of the arch's Pliocene subsidence history. This cryptic subsidence is reconstructed from low-grade metamorphic assemblages and compaction granulation textures in cores, and truncated down-hole thermal gradients from deep wells. These constraints indicate >1400m of cryptic Pliocene subsidence in the crest area of the arch, and a comparable additional minimum Quaternary uplift component to that which is expressed by topography and erosion. Pliocene-Quaternary facies relations are lost across the crest area of the arch, although depositional environments represented by the upper Miocene-Pliocene Kern River, Etchegoin and San Joaquin formations, as preserved off the flanks of the arch, suggest that a fluvial plain-deltaic environment faced northwest across the southern arch and graded northwestwards into a Pliocene marine embayment that developed across the former northern shelf edge of the SJB. How far to the east this facies system once lapped across recently exhumed western Sierra basement is poorly constrained. As the arch began its uplift in the latest Pliocene the marine embayment persisted in the eastern Tulare sub-basin. Lingering late Quaternary subsidence in the eastern Tulare sub-basin is marked by fluvial plain burial of mountainous western Sierra topography. Use of the upper Miocene shallow marine Santa Margarita Fm. as a strand line datum constrained by the resolved cryptic subsidence-uplift signals produces subsidence and uplift rolling hinges that resemble vertical transients that arise in numerical models of epeirogenic deformation resulting from the progressive peeling away of mantle lithosphere during delamination. We posit that such transients along the eastern SJB resulted when the southern Sierra Nevada mantle lithosphere drip progressively detached in Pliocene-Quaternary time

2004), Topographic response to mantle lithosphere removal in the southern Sierra Nevada region, Calif

ABSTRACT Geological studies of mantle xenoliths entrained in late Neogene-Quaternary lavas from the southern Sierra Nevada region and regional geophysical studies suggest that the highdensity mantle lithosphere that formed beneath the Sierra Nevada batholith in conjunction with arc magmatism is being convectively removed as a ''drip'' structure. This structure, as imaged seismically, is roughly cylindrical in shape with a diameter of ϳ100 km, and extends to ϳ225 km depth. Centered above this structure is a region ϳ120 km in diameter that is undergoing active subsidence relative to adjacent regions. Such subsidence is seen in the active fluvial-alluvial sediment flooding of mountainous topography of the southwestern Sierra and in the development of the adjacent Tulare Lake basin of the San Joaquin Valley. Dynamic modeling of such upper-mantle drip structures predicts a phase of overlying surface subsidence during the most vigorous phase of drip formation. The southern Sierra upper mantle drip and the overlying crust appear to be in this phase of their dynamically coupled evolution

Temporal relations of three dimensional mantle lithosphere delamination resolved in southeastern Great Valley's subsidence-uplift history, Sierra Nevada Microplate, California

A synthesis of geophysical and geological data suggests that the eclogitic (arclogite) mantle lithosphere root that formed during Cretaceous arc magmatism beneath the southern Sierra Nevada (SN) and adjacent Great Valley (GV) has progressively delaminated in E to W, and subsequently in S to N directions during Pliocene-Quaternary time. Thermo-mechanical modeling predicts km-scale subsidence/uplift transients through the course of delamination. The current delamination hinge runs along the southeastern margin of the GV, and turns westwards towards the axial southernmost GV. The Tulare (sub-) basin of the GV lies west of the delamination hinge, above the area of lower crustal attachment of the residual arclogite root, with the delaminated portion of the root hinging down to the east and south into the underlying mantle. The “center” of Tulare basin records ~700 m of anomalous Pliocene-Quaternary tectonic subsidence, which occurred mainly during the E to W phase of delamination. The southern margin of Tulare basin is uplifted and eroded along the Kern Arch, a Quaternary epeirogenic uplift zone that continues eastwards into the western Sierra, where GPS monuments record the most rapid contemporary uplift rates of the entire SN. The southern segment of the delamination hinge curves westward and runs along the transition between Tulare basin and the Arch. Erosional truncation patterns of Cenozoic strata along the eastern margin of the Arch, along with subsurface data on: 1. mechanical granulation textures; 2. low grade metamorphic phases; 3. vitrinite reflectance; 4. detrital apatite (U-Th)/He ages; and 5. thermal modeling, - all indicate up to ~1500 m of Pliocene cryptic (total) subsidence and sedimentation prior to rapid Quaternary uplift of the Arch. The cryptic subsidence was in continuity with the anomalous subsidence recorded in Tulare basin, and follows the regional pattern of southward increasing sediment loading and total subsidence along the southern Great Valley. The Tulare-Kern Arch subsidence/uplift relationships record epeirogenic transients arising from the Pliocene phase of E to W delamination, followed by the Quaternary S to N phase of delamination. This transient pattern parallels rock uplift, and volcanic and thermal flux patterns of the adjacent southern SN

Topographic response to mantle lithosphere removal in the southern Sierra Nevada region, California

Geological studies of mantle xenoliths entrained in late Neogene–Quaternary lavas from the southern Sierra Nevada region and regional geophysical studies suggest that the high-density mantle lithosphere that formed beneath the Sierra Nevada batholith in conjunction with arc magmatism is being convectively removed as a “drip” structure. This structure, as imaged seismically, is roughly cylindrical in shape with a diameter of ~100 km, and extends to ~225 km depth. Centered above this structure is a region ~120 km in diameter that is undergoing active subsidence relative to adjacent regions. Such subsidence is seen in the active fluvial-alluvial sediment flooding of mountainous topography of the southwestern Sierra and in the development of the adjacent Tulare Lake basin of the San Joaquin Valley. Dynamic modeling of such upper-mantle drip structures predicts a phase of overlying surface subsidence during the most vigorous phase of drip formation. The southern Sierra upper mantle drip and the overlying crust appear to be in this phase of their dynamically coupled evolution

Sediment provenance and dispersal of Neogene–Quaternary strata of the southeastern San Joaquin Basin and its transition into the southern Sierra Nevada, California

We have studied detrital-zircon U-Pb age spectra and conglomerate clast populations from Neogene–Quaternary siliciclastic and volcaniclastic strata of the southeastern San Joaquin Basin, as well as a fault-controlled Neogene basin that formed across the southernmost Sierra Nevada; we call this basin the Walker graben. The age spectra of the detrital-zircon populations are compared to a large basement zircon age data set that is organized into age populations based on major drainage basin geometry of the southern Sierra Nevada and adjacent ranges. We find a direct sediment provenance and dispersal link for much of the Neogene between the Walker graben and the southeastern San Joaquin Basin. In early to middle Miocene time, this link was accented by the delivery of volcaniclastic materials into the southeastern Basin margin from the Cache Peak volcanic center that was nested within the Walker graben. In late middle Miocene through early Pleistocene time, this linkage was maintained by a major fluvial system that we call the Caliente River, whose lower trunk was structurally controlled by growth faults along the Edison graben, which breached the western wall of the Walker graben. The Caliente River redistributed into the southeastern San Joaquin Basin much of the ∼2 km of volcaniclastic and siliciclastic strata that filled the Walker graben. This sediment redistribution was forced by a regional topographic gradient that developed in response to uplift along the eastern Sierra escarpment system. The Caliente River built a fluvial-deltaic fan system that prograded northwestward across the lower trunk of the Kern River and thereby deflected the Kern drainage flux of sediment into the Basin edge northward. In mainly late Miocene time, turbidites generated primarily off the Caliente River delta front built the Stevens submarine fan system of the southeastern and central areas of the San Joaquin Basin. In late Quaternary time, 1–1.8 km of Caliente River–built strata were eroded as an epeirogenic uplift that we call the Kern arch emerged along the southeastern Basin margin, in response to underlying mantle lithosphere removal. The sediment that was eroded off the arch was redistributed mainly into the Maricopa and Tulare sub-basins that are located to the southwest and northwest, respectively, of the arch