Joel Edward Saylor

Anatolia has been a major thoroughfare for faunal migration, and its paleogeography impacted faunal dispersal among Africa, Europe, and Asia. Delays in faunal migration from Africa into and through Anatolia and differences in faunal populations between Europe and Anatolia are evident in the Early Miocene record despite the prior closure of seaways separating the continents. We suggest that high elevations in western Anatolia posed migration barriers, leading to the observed delays. To test this hypothesis, we calculated paleoelevations based on hydrogen isotopic ratios of 12 volcanic glass samples and oxygen isotopic ratios of 25 new and 117 published carbonate samples. We constrained new sample ages to 19–16 Ma based on detrital and volcanic zircon U-Pb geochronology. Volcanic glass samples yielded δDpaleowater values ranging from −113.7‰ to −67.5‰, and alluvial paleosol carbonates yielded δ18Opaleowater values ranging from −13.7‰ to −7.5‰. The δ18Opaleowater value (−4.7‰) from an Oligocene marginal marine paleosol sample is consistent with the δ18O values (−5.6‰ to −4.3‰) of precipitation from Global Network of Isotopes in Precipitation (GNIP) stations on the SW Anatolian coast and provides a low-elevation baseline for paleoelevation calculations. Application of a thermodynamic Rayleigh distillation lapse rate to the mean values of the most negative quartile of δ18Opaleowater (−9.6‰) and δDpaleowater values (−75.5‰) yielded 19–16 Ma paleoelevations for western Anatolia of 3.6 ± 0.5 km and 3.9 ± 0.5 km (1σ), respectively. We conclude that the Early Miocene topography in western Anatolia was ~2 km higher than the current topography, consistent with the hypothesis that high Early Miocene paleoelevations in western Anatolia hampered faunal dispersal.

Biogeodynamics research seeks to link lithospheric scale processes with surface ecosystem evolution. Western Anatolia-Aegean region provides a critical testing ground for this coupling, where mantle dynamics have driven dramatic topographic reversals. Tectonostratigraphic and geomorphic insights indicate that Western Anatolia maintained elevated landscapes prior to and through Early Miocene extension. These observations are inconsistent with simple rift-related thinning but support dynamic uplift driven by removal of dense lithospheric mantle. Here, we integrate geodynamic modeling with geological observations to reconstruct the region's paleoelevation and its control on intercontinental faunal connectivity. Our results indicate that lithospheric delamination (slab peel-back) was the primary driver of Early Miocene topography. Numerical models show that slab peeling from beneath the crust and subsequent asthenospheric upwelling triggered a transient surface uplift of > 1 km and southward younging volcanism from İzmir-Ankara suture to the western Taurides. Supported by metamorphic constraints indicating crustal thickness consistent with elevations of 2–3 km, these results are in good agreement with the existence of a paleo-"Anatolian Highland" at ~20 Ma. Crucially, this geodynamically sustained topography acted as a significant biogeographic barrier. Synthesizing our models with recent fossil record analyses, we suggest that high elevations delayed faunal migration between Eurasia and Afro-Arabia, severing connectivity despite the closure of the Neo-Tethys. The timing of increased biotic interchange in the Middle–Late Miocene coincides with evidence for topographic lowering linked to post-delamination driven by crustal stretching. We conclude that the thermal and mechanical evolution of the Anatolian lithosphere exerted a first-order control on the timing of biotic exchange, highlighting the direct link between lithosphere dynamics and vertebrate evolution.

Climate models run under warmer‐than‐modern conditions indicate that hurricanes pass closer to the US East Coast and show that a higher proportion of tropical cyclones achieve “major hurricane” strength with winds >209 km/hr. Empirical observations indicate that the dominant southward longshore current direction off the US East Coast is reversed during passage of tropical cyclones and that the duration of the reversal is longer with cyclones that pass closer to the coast. Inland or coast‐proximal hurricane tracks place the strongest northward‐directed winds over the shallow marine shelf resulting in northward longshore currents, with velocities sufficient to move zircon grains in inner‐shelf marine waters. We use these observations to hypothesize that detrital zircon sediment provenance in warmer‐than‐modern conditions would be dominated by southern Appalachian and Piedmont sources. We test this hypothesis by conducting U‐Pb analysis of detrital zircons from Miocene through modern samples from the Chesapeake Bay area (Calvert Cliffs, Maryland), midway between Newfoundland and Georgia. Modeling of the detrital zircon data using non‐negative matrix factorization yields endmembers that are similar to potential empirical sources spanning the coastline from Newfoundland to Georgia. Forward linear mixing with those empirical sources shows that there is a shift from southern‐dominated sources during the Miocene Climatic Optimum (MCO) to northern‐dominated sources during the Middle Miocene Climatic Transition. The same northern sources dominate modern beach samples. We conclude that the sediment provenance data support the hypothesis that there is a greater proportion of stronger hurricanes and that they pass closer to the coastline during warmer‐than‐modern climates.

Whereas the ability to acquire petrochronological data from detrital minerals has exploded, development of tools to analyze and interpret the multivariate data sets has not kept pace. Herein, we present a case study, which applies the recently developed non‐negative Tucker‐1 decomposition (NNT1) method to a multivariate detrital zircon data set from till samples collected above the Cu‐bearing Guichon Creek Batholith in southern British Columbia, Canada. Zircon composition variables that we consider include age, Ce anomaly, Ce _N /Nd _N , Dy _N /Yb _N , ΔFMQ, Eu anomaly, ΣHREE/ΣMREE, Hf, Th/U, Ti temperature, and Yb _N /Gd _N . The NNT1 approach successfully deconvolves the multivariate data set into two endmembers, which are consistent with derivation either from non‐oxidized and relatively anhydrous (i.e., low Cu‐ore potential, Source 1) or oxidized and hydrous (i.e., potential Cu‐ore bodies, Source 2) igneous rocks. Furthermore, we attribute each of the zircon grains to either the Source 1 or 2 endmember based on maximization of the likelihood that their measured multivariate geochemistry was drawn from one or the other of the learned multivariate endmembers. Finally, we demonstrate that the proportions of the Source 2 endmember decrease with increasing distance from the ore bodies, as expected due to down‐ice or off‐axis zircon mixing and dilution. We conclude that the NNT1 approach provides insight into geologically meaningful sediment transport processes and multivariate sediment sources even when those sources are unknown. It thus provides a basis for future petrochronological interpretations with applied and pure geoscience applications.

Western Turkey underwent episodic N-S extension following a Late Cretaceous–Paleogene compressional regime. This extension resulted in the formation of the N-S-oriented Selendi and Gördes basins, as well as the E-W-trending Alaşehir Basin. However, the timing of basin formation is debated, hampering geodynamic model development or links to causal mechanisms. Here, we test whether N-S- and E-W-trending basins formed synchronously by determining maximum depositional ages from detrital zircon or stratigraphic ages from zircon-bearing tuffs in the basin fill of the Gördes and Alaşehir Basins.Existing basin chronology for the Gördes Basin is inferential and inconsistent. Previous research suggests the onset of sediment accumulation in the Gördes Basin occurred between 24.1 and 21.7 Ma. However, the older age is based on K-Ar dating of dikes that cross-cut the basement of the Gördes Basin and are lithologically correlated to clasts in the lower basin fill. The younger age comes from the tuffaceous uppermost formation and, therefore, represents a minimum age for the basin fill. K-Ar ages from volcanic domes underlying the oldest stratigraphy in the center of the Gördes Basin range from 18.4 ± 0.8 Ma to 16.3 ± 0.5 Ma, implausibly implying they erupted after the surrounding basin fill was deposited. This discrepancy suggests that either the age of the basin fill or the conclusion that the igneous rocks are volcanic is incorrect.The age of the Alaşehir Basin is based primarily on palynological biostratigraphy and magnetostratigraphy. Both yield middle Miocene ages (~16.4–14.4 Ma), but it is unclear whether these represent the oldest stratigraphy in the basin. Detrital zircon provenance data indicate that the earliest basin-filling sediments in the Gördes Basin were derived from a mixture of sources with affinities to the Tauride and Anatolide belts. Sediment provenance changes rapidly upsection, and within 50 meters, the Anatolide source is absent. In the Alaşehir Basin, the Anatolide source is never present, and sediment provenance is dominated by Tauride sources from the onset of basin filling.Preliminary chronostratigraphic data indicate that the onset of sediment accumulation in the Alaşehir and Gördes basins may be synchronous but also highlight significant problems with the stratigraphic model for the Gördes Basin. Data from a sandstone in what is considered the lowermost formation of the Gördes Basin yield a maximum depositional age of 17.5 ± 0.2 Ma, younger than the oldest reported K-Ar ages of 21.7–20.5 Ma. A stratigraphically higher tuffaceous sample from the same formation yields an upward-younging age of 16.9 ± 1.7 Ma. However, two ignimbrite samples from what is considered a younger formation yield ages of 18.2 ± 2.8 Ma. These age inversions and stratigraphic inconsistencies indicate significant issues with the stratigraphic model for the basin. In comparison, a sandstone sample from the lowermost formation of the Alaşehir Basin yields an age of 19.0 ± 2.9 Ma. We conclude that the onset of sedimentation in the two basins is synchronous within the resolution of our methods, but significant work is needed to determine more precise basin chronologies and resolve apparent age inversions in the Gördes Basin.

Detrital petrochronology is a powerful method of characterizing sediment and potentially sediment sources. The recently developed Tucker-1 decomposition method holds promise of using detrital petrochronology to identify both sediment-source characteristics and the proportions in which sources are present in sink samples even when sediment sources are unknown or unavailable for sampling. However, the correlation between endmember characteristics and lithological sources or proportions and sedimentary processes has not been established. Herein we present a case study of the recently developed Tucker-1 decomposition method to a multivariate geochemical data set from detrital zircons in till samples collected above the Cu-bearing Guichon Creek Batholith (GCB) in southern British Columbia, Canada. Data include a suite of eleven variables, including age, Ce anomaly, CeN/NdN, DyN/YbN, ΔFMQ, Eu anomaly, ΣHREE/ΣMREE, Hf, Th/U, Ti temperature, and YbN/GdN, from 12 samples from collected at a range of distances in the down ice-flow direction from the GCB.We demonstrate that endmember modelling using the Tucker-1 decomposition method successfully deconvolves the multivariate data sets into two endmembers in which the geochemical distributions are consistent with derivation from either non-oxidized and relatively anhydrous (i.e., low ore potential, Source 1) or oxidized and hydrous (i.e., potential ore bodies, Source 2) igneous rocks. Furthermore, we demonstrate that the proportions of the Source 2 endmember decrease with increasing distance from the ore bodies, as expected due to downstream zircon mixing and dilution.Finally, we attribute each of the zircon grains to either the Source 1 or 2 endmember based on maximization of the likelihood that their measured multivariate geochemistry was drawn from one or the other of the learned multivariate endmembers. We compared these grain attributions to the results of an independent Classification and Regression Tree (CART) analysis designed to characterize zircon grains as either “fertile” or “barren” with respect to copper based on their geochemistry. We find that there is ~80% overlap between the source attributions based on the CART analysis and the grain-source identification based on the Tucker-1 decomposition.We conclude that the novel Tucker-1 decomposition approach provides a flexible, precise, and accurate method of characterizing multivariate sediment sources even when those sources are unknown. It thus provides a basis for future petrochronological interpretations with applied and pure geoscience applications. All of the analyses presented herein can be freely accessed through a web application (https://dzgrainalyzer.eoas.ubc.ca/) or open-source Julia code (https://github.com/MPF-Optimization-Laboratory/MatrixTensorFactor.jl).

Anatolia is a major thoroughfare for faunal migration and its paleogeography impacted faunal dispersals from, and to, Africa, Europe, and Asia. For example, the first appearance of hominoids in central Anatolia was 2-6 Myr after the formation of the "Gomphotherium Landbridge" according to fossil records, yet the arrival of hominoids at a far more distant location in China occurred only 1-2 Myr after the formation of the landbridge. Furthermore, in the early Miocene, the populations of small mammals in Europe and Anatolia differed greatly. Mineral barometry-based crustal thickness calculations and Airy isostatic considerations suggest paleoelevations of 3.5–4.1 km in early Miocene western Anatolia. This presents the possibility that the observed delays in faunal dispersion and differences in faunal populations were the result of topographic barriers in western Anatolia. Nevertheless, the hypothesis that high elevations posed migration barriers in western Anatolia lacks supporting paleoelevation data. To test the hypothesis, we first established a new geochronological model for the Gördes Basin based on U-Pb ages from sandstones and tuffs collected from new stratigraphic sections and then measured hydrogen isotopic ratios of 13 volcanic glass samples and oxygen isotopic ratios of 28 carbonate samples from that basin. The onset of the sedimentation of the Gördes Basin at 18-19 Ma based on both maximum depositional ages (sandstone) and true depositional ages (tuffs) is younger than previously estimated at 21-20 Ma. We calculated the paleowater isotopic compositions with standard isotopic fractionation during precipitation and a 15°C precipitation temperature for CO3. Volcanic glass samples have δDpaleowater(pw) values ranging from -113.7 to -67.5‰ and δ18Opw values ranging from -12.9 to -6.1‰. Hydration by primarily ambient waters rather than magmatic water is indicated by a slight negative trend between δD and weight percentage H2O. The analysis of the δ18O and δ13C of alluvial carbonate samples and microphotographs demonstrate that they are not diagenetic. Paleoelevation was calculated using alluvial carbonate materials and volcanic glass samples with wt% H2O> 2. A 16 Ma paleosol sample in a marginal marine environment was chosen as a low-elevation baseline for determining Miocene paleoelevations. Calculated paleoelevations of 19-16 Ma western Anatolia are 3.6 ± 0.7 and 4.3 ± 0.9 km (1σ), based on the most negative δ values of -12.9‰ and -113.7‰ for δ18Opw and δDpw, respectively. Paleoelevations calculated based on the most negative quartile are 3.2 ± 0.5 km and 3.9 ± 0.6 km (2σ) for δ18Opw and δDpw, respectively.We conclude that the early Miocene topography in western Anatolia was approximately 2-3 km higher than the current topography, based on independent oxygen and hydrogen isotopic compositions of carbonate and volcanic glass paleoelevation proxies. Moreover, independent estimations based on Airy isostacy agree with the calculated paleoelevations. These factors together support the model of extreme early Miocene paleoelevations in western Anatolia and the hypothesis that early Miocene faunal dispersal was hampered by high relief. If that is the case, extensional deformation throughout the Miocene-Pliocene could cause a decrease in paleoelevation and an establishment of faunal migration corridors in the western Anatolia.

Source‐to‐sink systems respond to and therefore potentially record topographic and tectonic changes. North of the Tian Shan Belt, the Sikeshu subbasin of the SW Junggar Basin transitioned from active extension in the Triassic to post‐extensional subsidence in the Jurassic‐Cretaceous. Sediment in the Sikeshu subbasin has been shown to be derived from the Tianshan. However, the details of the source‐to‐sink system remain unclear and discrepancies exist between proxy records. The heavy minerals in the Middle Triassic in the Sikeshu subbasin are dominated by garnets. To investigate the garnet sources and decipher the Mesozoic source‐to‐sink evolution, we conducted petrological and sedimentary analysis and detrital garnet and tourmaline geochemistry. We found that the geochemistry of garnets in the Middle Triassic sandstone is most consistent with that of the skarns in the Yili Block (YB) in Tianshan, while the geochemistry of 55%–84% of garnets in other Mesozoic sandstones is consistent with that of garnets in amphibolites in the YB. The geochemistry of the tourmalines since the Upper Triassic is consistent with that of the meta‐sedimentary rocks in the YB and Central Tianshan Block. The dominance of garnets sourced from skarns in the Middle Triassic probably indicates a near‐source point provenance and the broader range of garnet compositions from the Upper Triassic–Lower Cretaceous suggests multiple sources. We infer that the point source changed to multiple sources, which is consistent with the zircon spectra changing from unimodal to multimodal. This change reflects the expansion of the drainage that accompanies a change from active rifting to a post‐rift stage.