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Faults on microcontinents record the dynamic evolution of plate boundaries. However, most microcontinents are submarine and difficult to study. Here, we show that the southern part of the Isla Ángel de la Guarda (IAG) microcontinent, in the northern Gulf of California rift, is densely faulted by a late Quaternary‐active normal fault zone. To characterize the onshore kinematics of this Almeja fault zone, we integrated remote fault mapping using high‐resolution satellite‐ and drone‐based topography with neotectonic field‐mapping. We produced 13 luminescence ages from sediment deposits offset or impounded by faults to constrain the timing of fault offsets. We found that north‐striking normal faults in the Almeja fault zone continue offshore to the south and likely into the nascent North Salsipuedes basin southwest of IAG. Late Pleistocene and Holocene luminescence ages indicate that the most recent onshore fault activity occurred in the last ∼50 kyr. These observations suggest that the North Salsipuedes basin is kinematically linked with and continues onshore as the active Almeja fault zone. We suggest that fragmentation of the evolving IAG microcontinent may not yet be complete and that the Pacific‐North America plate boundary is either not fully localized onto the Ballenas transform fault and Lower Delfin pull‐apart basin or is in the initial stage of a plate boundary reorganization.

 

Significant sediment flux and deposition in a sedimentary system are influenced by climate changes, tectonics, lithology, and the sedimentary system's internal dynamics. Identifying the timing of depositional periods from stratigraphic records is a first step to critically evaluate the controls of sediment flux and deposition. Here, we show that ages of single‐grain K‐feldspar luminescence subpopulations may provide information on the timing of previous major depositional periods. We analyzed 754 K‐feldspar single‐grains from 17 samples from the surface to ∼9 m‐depth in a trench located downstream of the Mission Creek catchment. Single‐grain luminescence subpopulation ages significantly overlap at least eight times since ∼12.0 ka indicating a common depositional history. These depositional periods correspond reasonably well with the Holocene intervals of wetter than average climate conditions based on hydroclimatic proxies from nearby locations. Our findings imply a first‐order climatic control on sediment depositional history in southern California on a millennial timescale.

 

Drone image-derived digital elevation model at 'incised terrace' site in "Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México" created with Agisoft Photoscan software. WGS1984 UTM Zone 12N. 

Drone image-derived digital elevation model at sag pond site in "Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México" created with Agisoft Photoscan software. WGS1984 UTM Zone 12N. 

This is the 3-m resolution digital elevation model from "Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México". Digital elevation was constructed from two 0.5-m resolution Pleiades satellite images (product type: 50cm Panchromatic + 2m (4-Band) Multispectral Bundle) using the NASA Ames Stereo Pipeline software. WGS1984 UTM Zone 12N. 

Drone image-derived digital elevation model at 'flight of terraces' site in "Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México" created with Agisoft Photoscan software. WGS1984 UTM Zone 12N. 

Drone image-derived digital elevation model at 'southern terraces' site in "Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México" created with Agisoft Photoscan software. WGS1984 UTM Zone 12N. 

Dosimetry data, equivalent doses, and single grain post-infrared infrared stimulated luminescence (p-IR IRSL) ages from "Microcontinent Breakup and Links to Possible Plate Boundary Reorganization in the Northern Gulf of California, México". Also shown in Table S2 of publication's supplementary file. 

Tectonic deformation can influence spatiotemporal patterns of erosion by changing both base level and the mechanical state of bedrock. Although base-level change and the resulting erosion are well understood, the impact of tectonic damage on bedrock erodibility has rarely been quantified. Eastern Tibet, a tectonically active region with diverse lithologies and multiple active fault zones, provides a suitable field site to understand how tectonic deformation controls erosion and topography. In this study, we quantified erosion coefficients using the relationship between millennial erosion rates and the corresponding channel steepness. Our work shows a twofold increase in erosion coefficients between basins within 15 km of major faults compared to those beyond 15 km, suggesting that tectonic deformation through seismic shaking and rock damage significantly affects eastern Tibet erosion and topography. This work demonstrates a field-based, quantitative relationship between rock erodibility and fault damage, which has important implications for improving landscape evolution models.