Sedimentation and basin evolution during initial marine flooding into the Gulf of California: Late Miocene Boleo Formation, Baja California Sur, México

Gulf surges are transient disturbances that propagate along the Gulf of California (GoC) from south to north, transporting cool moist air toward the deserts of northwest Mexico and the southwest United States during the North American monsoon. They have been shown to modulate precipitation and have been linked to severe weather and flooding in northern Mexico and the southwest United States. The general features and progression of surge events are well documented but their detailed dynamical evolution is still unclear. In this study, a convection-permitting simulation is performed over the core monsoon region for the 12–14 July 2004 gulf surge event and the dynamics of the simulated surge are examined. Initially, convection associated with the tropical easterly wave precursor to Tropical Cyclone Blas creates a disturbance in the southern GoC on early 12 July. This disturbance is a precursor to the gulf surge on 13 July and is a Kelvin shock (internal bore under the influence of rotation) that dissipates in the central GoC. The surge initiates from inflow from the mouth of the GoC along with convective outflow impinging on the southern GoC. Continued convective outflow along the GoC generates multiple gravity currents and internal bores while intensifying the simulated surge as it propagates up the GoC. As the core of the surge reaches the northern GoC, a Kelvin shock is again the best dynamical fit to the phenomenon. Substantial low-level cooling and moistening are associated with the modeled surge along the northern GoC as is observed.

Acanthemblemaria balanorum Brock (Clubhead Blenny; Fig. 1) is a chaenopsid tube blenny endemic to the Tropical Eastern Pacific. Adults of this species, as all members of the Chaenopsidae, inhabit vacated invertebrate tubes or tests (Stephens 1963; Lindquist 1985). In the case of A. balanorum, the shelter of choice is the vacated test of Megabalanus Hoek barnacles, a genus characterized in the Tropical Eastern Pacific by a complex of species (Henry and McClaughlin 1986) that typically live in the upper 10 m on shallow rocky reefs (Brusca and Hendrickx 2008). In the Gulf of California (GOC), Mexico, A. balanorum overlaps in distribution with two congeners, A. crockeri Beebe and Tee-Van and A. hastingsi Lin and Galland, and these species are known to exhibit depth partitioning, with A. balanorum inhabiting relatively shallower depths, A. crockeri inhabiting relatively deeper depths, and A. hastingsi overlapping near the edges of the depth ranges of the other two species at intermediate depths (Lindquist 1985). A detailed study of the relationships among these three congeners in the southern GOC (Lindquist 1985) reported that A. balanorum inhabits shelters (5barnacles) down to approximately 7 m depth. Guides to the fishes of the region (e.g., Allen and Robertson 1994; Humann and DeLoach 2004) report a similar depth range. In November 2010, I observed and collected several individuals of A. balanorum at a depth of 21 m at the base of a pinnacle off the south end of Maria Cleofas, the southernmost point in the Islas Marias archipelago, southern GOC. These individuals, like all individuals of this species that I have observed, inhabited vacant barnacles (Megabalanus). This observation represents a significant depth range extension for this normally shallow subtidal fish (and may also represent an extension for the barnacle; Brusca and Hendrickx 2008). This ability of a microhabitat specialist to colonize abnormal macrohabitats (in this case much deeper than normal waters) when its microhabitat (5barnacles) is available supports a hypothesis that these specialists are resource (5shelter) limited. Similar shelter limitation has already been experimentally demonstrated in the GOC congener, A. crockeri, which increases in average density with shelter addition (Hastings and Galland 2010). I observed additional evidence that A. balanorum is a shelter-limited microhabitat specialist in July 2009 at Las Animas, a small island and a series of small pinnacles in the central GOC. That site proved to be ideal A. balanorum habitat, with several large boulders completely covered by broad, very dense Megabalanus fields down to 5 m depth. Within these barnacle fields, I observed large numbers of A. balanorum, more densely distributed than any other chaenopsid population reported to date (e.g. in Lindquist 1985; Clarke 1996; Thomson and Gilligan 2002; P.A. Hastings, pers. comm.). During an opportunistic survey of the area, I placed a 0.25 m quadrat on five randomly selected areas on the top of a large, flat boulder at 5 m depth in order to survey chaenopsids and Bull. Southern California Acad. Sci. 110(2), 2011, pp. 52–55 E Southern California Academy of Sciences, 2011

Geomagnetic field variations have been observed at four stations in the central Gulf of California and at one Pacific coast station at the same latitude. The four Gulf stations comprise two pairs of stations on opposite sides of the Gulf; one pair, at El Barril and Bahia Kino, was placed across what was thought to be a long section of transform fault in the Gulf and the second pair, at Mulege and Guaymas, was placed across the Guaymas basin which is a proposed site of an ocean ridge type spreading centre. Variations in the vertical component of the magnetic field show almost complete reversal on opposite sides of the Gulf in the frequency range 0.25–4.0 c hr-1. Analysis of the data indicates that induced electric currents flow in and under the Gulf of California. Models for 1 chr-1 suggest that the surface conductor alone is insufficient to account for the surprisingly large anomaly between El Barril and Bahia Kino. Although only a small number of data points is available it is thought that this anomaly indicates the possible existence of a spreading centre between these two stations. The suggestion is therefore made that the fracture pattern for the central Gulf of California includes a spreading centre at the San Pedro Martir basin. A consequence of this is that the fracture pattern must change with time. No explanation of this changing fracture pattern is attempted but its occurrence would account for the presence of the many islands in the Gulf of California.

Clay dispersal and the geochemistry of manganese in the Northern Gulf of California

Research Article| February 01, 2013 Thick evaporites and early rifting in the Guaymas Basin, Gulf of California Nathaniel C. Miller; Nathaniel C. Miller * 1Marine Geology and Geophysics, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program, 266 Woods Hole Road, Woods Hole, Massachusetts 02543, USA *E-mail: ncm@mit.edu. Search for other works by this author on: GSW Google Scholar Daniel. Lizarralde Daniel. Lizarralde 2Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, Massachusetts 02543, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Nathaniel C. Miller * 1Marine Geology and Geophysics, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program, 266 Woods Hole Road, Woods Hole, Massachusetts 02543, USA Daniel. Lizarralde 2Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, Massachusetts 02543, USA *E-mail: ncm@mit.edu. Publisher: Geological Society of America Received: 14 Jun 2012 Revision Received: 12 Sep 2012 Accepted: 21 Sep 2012 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2013 Geological Society of America Geology (2013) 41 (2): 283–286. https://doi.org/10.1130/G33747.1 Article history Received: 14 Jun 2012 Revision Received: 12 Sep 2012 Accepted: 21 Sep 2012 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Nathaniel C. Miller, Daniel. Lizarralde; Thick evaporites and early rifting in the Guaymas Basin, Gulf of California. Geology 2013;; 41 (2): 283–286. doi: https://doi.org/10.1130/G33747.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Multichannel seismic transects reveal an ∼2-km-thick, ∼50 × 100 km evaporite body under the shelf on the eastern margin of the Guaymas Basin, central Gulf of California (Mexico). These thick newly discovered evaporites appear to be correlated with well-known gypsum beds near Santa Rosalía to the northwest, on the Baja California peninsula. Closing the Gulf of California along kinematic flow lines suggests that the thin, scattered, ca. 7 Ma Santa Rosalía gypsum beds formed on the fringe of the much thicker evaporite deposit. This correlation, and the large volume of the Guaymas evaporates, implies that substantial marine incursions and subsequent evaporite deposition occurred during the Late Miocene and prior to lithospheric rupture. Furthermore, the shape of the Guaymas evaporite is indicative of a transtensional basin, suggesting that oblique extension existed in the central Gulf of California ca. 7 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Coccolithophore export production in Guaymas Basin, Gulf of California: response to climate forcing

Temporal variability of satellite chlorophyll-a as an ecological resilience indicator in the central region of the Gulf of California

The oegopsid squids Abraliopsis and Pterygioteuthis are abundant and diverse genera with taxonomic and distributional problems. Identification and distribution of species in the Mexican Pacific has been somewhat controversial. Here are provided a large series of new records for Abraliopsisaffinis, Abraliopsisfalco, Pterygioteuthisgemmata, Pterygioteuthisgiardi and Pterygioteuthishoylei from the Gulf of California and off the SW coast of Mexico. All five species were collected in the central or the southern Gulf of California, or in both. Abraliopsisaffinis was found in seven samples with a total of 48 specimens, from 21°59' to 24°53'12"N. Abraliopsisfalco was much less represented in the samples (14 specimens) but it was found in 10 localities, four of which correspond to the central-southern Gulf of California (north to 27°44'53"N) and six to SW Mexico (south to 16°49'18"N). In the case of Pterygioteuthisgemmata, only two records (three specimens) were obtained, both in the SW Gulf of California, while Pterygioteuthisgiardi (nine specimens) records were all from the central Gulf of California (27°44'53” to 25°39'59"N). In the case of Pterygioteuthishoylei (nine specimens), material was obtained in six localities, also in a restricted latitudinal range (24°23'48” to 25°56'56"N).

Distribution of silicoflagellates in plankton and core top samples from the Gulf of California

The fin whales ( Balaenoptera physalus ) in the Gulf of California comprise a resident population genetically isolated from the rest of the North Pacific. The species occurs in the Eastern Midriff Islands Region (EMIR), in the central Gulf of California. The present study estimated fin whale abundance and apparent survival using photo‐identification data collected via weekly small‐boat surveys conducted from 2009 to 2017. In total, 1082 fin whales were recorded during 287 surveys that totaled 1924 h of research effort. After a photo comparison process of the dorsal fin, 376 unique individuals were identified, of which 180 had distinct features and high‐quality photos to be included in the mark‐recapture analysis. A mark ratio of 0.615 was obtained. A Jolly–Seber/POPAN mark‐recapture model yielded a superpopulation size of = 360 (SE Un = 34.4, 95% CI [304–429]). The estimates for the years 2010–2016 were similar, from 178 (95% CI [185–363]) to 259 (95% CI [179–375]). A Cormack‐Jolly‐Seber model was used to estimate probability of survival. A hierarchical Bayesian time series analysis of encounter rates collected from 2012 to 2017 showed evidence of seasonality, with whales mostly present during the cold season (December–May), which coincides with the local upwelling regime. This information adds to the value of the EMIR as an important area for fin whale conservation in the Gulf of California.

Seasonal and annual variability in particle fluxes in the Gulf of California: A response to climate forcing

Interannual response of euphausiid community abundance during the anomalous warming period (2014–2016) in the Gulf of California

Rifts in the interior of continents that evolve to form large oceans typically last for 30 to 80 m.y. and longer before complete rupture of the continent and onset of sea-floor spreading. A distinct style of rifts form along the active tectonic margins of continents, and these rifts more commonly form marginal seas and terranes or continental blocks or slivers that are ruptured away from their home continent. The Gulf of California and the Baja California microplate make up one of the best examples of the latter setting and processes. In the southern Gulf of California, sea-floor spreading commenced only ~6–10 m.y. after the formation of the oblique-divergent plate boundary at ca. 12.5 Ma. Three main factors caused this rapid rupture: (1) an inherited long, narrow belt of hot, weak crust from a volcanic arc that was active immediately before formation of the oblique-divergent plate boundary and that lay between two strong batholith belts; (2) relatively rapid plate motion resulting in high strain rates; and (3) a dominant role of strike-slip faulting in the highly oblique-divergent setting that formed large pull-apart basins with rapid and focused crustal thinning in a linked en-echelon system. Accentuating factor 1 is that the formation of slab windows associated with microplate capture west of the Baja California peninsula may have further weakened the crust. These causes of rapid rupture of continental lithosphere are mostly linked to the fact that the Gulf of California developed along a long-lived tectonically active margin of a continent with a convergent or oblique-convergent setting since at least the Jurassic, but not a margin that was thickened in a major contractional orogen. This combination of causes and factors suggests that rifts that form at active margins are fundamentally different than continental interior rifts, and that these differences can produce vastly different rifting histories. The formation and northwestward motion of the Baja California microplate also show that “terranes” formed in an obliquedivergent setting can form and move long distances over relatively short geologic time intervals. INTRODUCTION The rupture of continental lithosphere is one of the most fundamental tectonic processes. Complete rupture of a continent requires the familiar progression from early rifting to extreme continental lithosphere thinning to continental breakup that forms oceanic spreading in a nascent ocean (e.g., Veevers, 1981). The development of a rift, and whether it progresses to breakup, is mainly dependent on the thermal structure, crustal thickness, and crustal strength of the lithosphere when rifting begins (e.g., Buck, 2007), as well as forces at the base of the lithosphere and far-field plate interactions (Ziegler and

Sources and hydrothermal alteration of organic matter in Quaternary sediments: A synthesis of studies from the Central Gulf of California

The use of mark-recapture data can be an alternative to other methods for estimating abundance of the jumbo squid Dosidicus gigas and can be used when catch-per-unit-effort data applied to depletion models or estimates from survey research are not available. Two mark- recapture events were analyzed in the central Gulf of California, Mexico, during October 2001 and April 2002 to assess the status of jumbo squid. Results from October 2001 yielded a population size of 20.2 million squid with a 95% CI of 16 to 26.5 million squid (p < 0.05). In April the popula- tion size was estimated at 132.6 million squid with a 95% CI of 85.5 to 222 million squid (p < 0.05). The results for October and April show 2 different periods of abundance. Estimates of tag return rates were higher in April (5.5%) than in October (1.7%), and recruitment is the most plausible explanation. In the Gulf of California, recruitment of jumbo squid commonly occurs during April and May.