Pigeon Point Research Articles

Multiple Avenues to Gender in Strawberries

ABSTRACTCommon strawberry cultivars are hermaphrodites, producing both anthers and pistils in their flowers. However, octoploid Fragaria species are trioecious and different genotypes can be female with pistillate flowers, hermaphrodites, or males with staminate flowers. One female selection, F. virginiana High Falls 22 and three hermaphrodite selections, N8688, RH23, and Montreal River 10 were hybridized with five June-bearing cultivars. Seedlings of each family were planted in Ontario and Michigan. Two F. chiloensis selections Pigeon Point (female) and FRA1267 (hermaphrodite), were hybridized with 14 F. virginiana selections. Seedlings from each family were planted in Ontario and Minnesota. In all progeny, the presence or absence of anthers was recorded and a subjective scale used to estimate the percentage of fruit set (1–10 representing 10% intervals). Also, FRA1267 was crossed with one F. × ananassa selection and the progeny intercrossed and grown in Ontario. In the sib-crosses gender was recorded. In two female parents, the female progeny had on average a higher fruit set than the hermaphrodite progeny. F. virginiana genotypes varied in their fruit set, which suggested that there are a number of alleles involved in the fertility of hermaphrodites. In crosses, FRA1267 produced 80% females when used as a female parent and 100% hermaphrodites when used as a male parent. It is thought that the trait is inherited cytoplasmically or that the F. chiloensis alleles involved are epistatic when F. virginiana or F. × ananassa is used as a male parent.

Hydrodynamic versus GIS modelling for coastal flood vulnerability assessment: Which is better for guiding coastal management?

Under climate change, sea-level rise and increasing storm surge intensity will increase the likelihood of floods for low-lying coastal areas. Therefore, Coastal Flood Vulnerability Assessments (CFVA) are necessary to inform decision making for coastal management, where applicable. Two types of tools, hydrodynamic models and Geographic Information Systems (GIS), are commonly employed for these evaluations. Using Pigeon Point, Southwest Tobago, as a case study, this paper compares the application of both to determine the best approach for CFVA that can be used to guide coastal management. For hydrodynamic modelling, available and surveyed data on bathymetry, topography and tides along with current and future estimates of mean sea-level were used to create a structured and an unstructured grid model via the LISFLOOD-FP and TELEMAC-2D codes, respectively. For the GIS assessment, a coastal digital elevation model was developed using the same data on bathymetry and elevation. These models were used to project the present and future impact of storm surges on coastal flood extent at Pigeon Point. Outputs generated were compared and analysed within a GIS. Using predictions from TELEMAC-2D (full shallow water equations) as the baseline for comparison, average results acquired revealed that projections generated by all three models were consistent (less than 5.00% difference in flood predictions). To add certainty to the modelling results, all models were used to simulate an observed spring high tide event for model validation purposes. The Root Mean Squared Error (RMSE) was calculated as an indication of model performance. RMSE values indicated that all models were consistent and matched well to the field observations. However, further analysis revealed that inherent in the use of GIS for CFVA is hydraulic connectivity issues due to exclusion of flow dynamics, which leads to over-estimation in flood extent. Acknowledging the theory that over-estimation leads to over-management, it is suggested that hydrodynamic models are better suited for detailed CFVA, while GIS can be used rapidly as a potential indicator of flood exposure for large sites.

Modelling coastal flood vulnerability: Does spatially-distributed friction improve the prediction of flood extent?

This paper examines whether the application of spatially-distributed versus static friction in hydrodynamic modelling increases the accuracy of predicted coastal flood extent using Pigeon Point, southwest Tobago, as a case in point. A two-dimensional hydrodynamic flood model is created from acquired and surveyed bathymetric, topographic and tidal data via the LISFLOOD-FP model code. Using a Landsat 8 image of the study area, a Maximum Likelihood (ML) supervised classification was performed to distinguish different land cover classes within the study site. The classified Landsat 8 image was further processed by assigning friction values to each land cover class to create a spatially-distributed friction file in ASCII format for use in LISFLOOD-FP. Using the flood model developed, simultaneous simulations were performed to assess the impact of storm surges (varying levels) on coastal flood extent at Pigeon Point utilising a static friction value, which broadly defined the area (i.e., 0.02), and the spatially-distributed friction file generated. Model outputs were compared to determine the extent of difference in flood prediction obtained from the application of static versus spatially-distributed friction through a Geographic Information System (GIS) based analysis. The flood model developed was subsequently applied to simulate an observed spring tide event using both static and spatially-distributed friction value(s) defined and model performance in each case was evaluated using the Root Mean Squared Error (RMSE) approach. Collated results indicated that using spatially-distributed over static friction do not increase accuracy of predicted coastal inundation extent, nor improve model performance. However, it appears to provide more insight on flood timings, which can be useful for coastal management.

In vitro screening of octoploid Fragaria chiloensis and Fragaria virginiana genotypes against iron deficiency

Iron (Fe) deficiency is one of the common problems in strawberry (Fragaria × ananassa Duch.) growing regions. In vitro screening enables researchers to evaluate genotype performance under several concentrations of Fe in a relatively fast and economical way. Therefore, we evaluated the responses of several genotypes belonging to octoploid Fragaria chiloensis (L.) Mill. and Fragaria virginiana Mill. (the progenitors of cultivated strawberry) against Fe treatments under in vitro conditions. In the first experiment, HM 1, Pigeon Point, CFRA1267 (F. chiloensis subsp. pacifica), and CA1541 (F. chiloensis subsp. chiloensis) were tested with various Fe concentrations (0%, 10%, 15%, 25%, 50%, 65%, 80%, and 100%, where 100% = 27.8 mg L^{-1} FeSO_4.7H_2O). Different Fe concentration treatments resulted in differences in plant height, fresh and dry weight, as well as macro- and microelement concentrations among the tested genotypes. In the second experiment, 16 octoploid Fragaria genotypes were tested with 4 Fe concentration treatments (0%, 10%, 50%, and 100%, where 100% = 27.8 mg L^{-1} FeSO_4.7H_2O). Iron concentration and genotype interactions were significant for all studied characteristics except sulfur (S) and manganese (Mn) concentrations, and the 16 genotypes responded differentially to varying Fe treatments. The results of these experiments indicated that F. chiloensis and F. virginiana genotypes exhibited considerable variation under different Fe treatments in vitro, and the more resistant genotypes could be utilized to develop new strawberry cultivars with tolerance to low Fe concentrations.

Salinia revisited: a crystalline nappe sequence lying above the Nacimiento fault and dispersed along the San Andreas fault system, central California

Salinia revisited: a crystalline nappe sequence lying above the Nacimiento fault and dispersed along the San Andreas fault system, central California

The use of integrated sedimentological and geophysical methods in drumlin research – a case study of Pigeon Point, Clew Bay, Northwest Ireland

ABSTRACTDespite significant advances over the past decades, our understanding of drumlin formation and associated ice‐bed processes is still incomplete. In this paper, we present the integrated use of geomorphological, sedimentological and geophysical techniques as a powerful means to force a breakthrough towards solving the drumlin enigma.We report on investigations of the anatomy of the Pigeon Point drumlin, Clew Bay, Ireland. We found that the bulk of the landform, which displays a classical drumlin shape, consists of silty‐clayey diamicton showing evidence of deformation, hydrofracturing and comminution. The unit is interpreted as a sub‐glacial traction till/comminution till. The thin unit overlying this basal till consists of silty‐sandy diamicton, and is interpreted as a para‐glacially modified melt‐out till. The partly cemented third unit consists of stratified, massive to graded sands and gravels. Its contact with the sub‐glacial traction till consists of a series of concave shapes, which suggests that it was deposited in meltwater channels that flowed in sub‐glacial cavities and that cut laterally into the drumlin.We propose that highs in the undulating rockhead relief, as shown in the seismic profile, have provided nuclei which initiated drumlin formation. This idea is supported by the observation of local detached bedrock slabs that grade upwards into a comminution till. In the long profile, very high normalized induced polarization (IP) values form a wedge‐shape, which is interpreted as a set of conjugate thrusts, or a ‘pop‐up’ structure. The structure is positioned directly above one of the undulations in the bedrock, suggesting a direct relationship. The high values are thought to reflect the presence of pre‐existing clays, which were sheared into the till, thus forming linings in the thrust features. It is concluded that glacitectonic processes, notably differential bedrock weathering and thrusting, have played a key role in the formation of this drumlin. Copyright © 2011 John Wiley & Sons, Ltd.

Zircon U-Pb age of the Pescadero felsite: A Late Cretaceous igneous event in the forearc, west-central California Coast Ranges

Weathered felsite is associated with the late Campanian–Maastrichtian Pigeon Point Formation near Pescadero, California. Poorly exposed, its age and correlation are uncertain. Is it part of the Pigeon Point section west of the San Gregorio–Hosgri fault? Does it rest on Nacimiento block basement? Is it dextrally offset from the Oligocene Cambria Felsite, ~185 km to the southeast? Why is a calc-alkaline hypabyssal igneous rock intrusive into the outboard accretionary prism? To address these questions, we analyzed 43 oscillatory-zoned zircon crystals from three incipiently recrystallized pumpellyite ± prehnite ± laumontite-bearing Pescadero felsite samples by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) techniques. Thirty-three zircons gave late Mesozoic U-Pb ages, with single-grain values ranging from 81 to 167 Ma; ten have pre-Mesozoic, chiefly Proterozoic ages. A group of the four youngest Pescadero zircons yielded an apparent maximum igneous age of ca. 86–90 Ma. Reflecting broad age scatter and presence of partly digested sandstone inclusions, we interpret the rest of the zircons (perhaps all) as xenocrysts. Twenty-three zircons were separated and analyzed from two samples of the similar Cambria Felsite, yielding a unimodal 27 Ma U-Pb age. Clearly, the origin of the Upper Oligocene Cambria Felsite is different from that of the Upper Cretaceous Pescadero felsite; these rocks are not correlated, and do not constrain displacement along the San Gregorio–Hosgri fault. Peak ages differ slightly, but relative probability curves for Mesozoic and pre-Mesozoic Pescadero zircons compare well, for example, with abundant U-Pb age data for detrital zircons from Franciscan metaclastic strata ~100 km to the east in the Diablo Range-San Francisco Bay area, San Joaquin Great Valley Group turbidites, Upper Cretaceous Nacimiento block Franciscan strata, and Upper Cretaceous forearc units of the Transverse Ranges. Based on zircon U-Pb ages, geologic and petrographic relations, the Pescadero felsite and a capping, sheared metaconglomerate underlie the Pigeon Point Formation. We infer that the magma formed by anatexis of Franciscan or Great Valley clastic sedimentary rocks originating from a parental Mesozoic Sierran-Mojave-Salinian calc-alkaline arc. The felsite erupted during Late Cretaceous time, was metamorphosed to pumpellyite-prehnite grade within the subduction zone, and then was rapidly exhumed, weakly zeolitized, and exposed before Pigeon Point forearc deposition. Pescadero volcanism apparently reflects a previously unrecognized ca. 86–90 Ma felsic igneous event in the accretionary margin.

Incorporation of Spatial and Economic Analyses of Human-Use Data in the Design of Marine Protected Areas

Social, economic, and ecological criteria contribute to the successful design, implementation, and management of marine protected areas (MPAs). In the context of California's Marine Life Protection Act Initiative, we developed a set of methods for collecting, compiling, and analyzing data about the spatial extent and relative economic importance of commercial and recreational fishing. We interviewed 174 commercial fishers who represented the major fisheries in the initiative's north-central coast region, which extends from Point Arena south to Pigeon Point. These fishers provided data that we used to map the extent of each of the fishing grounds, to weight the relative importance of areas within the grounds, to characterize the operating costs of each fishery, and to analyze the potential economic losses associated with proposed marine protected areas. A regional stakeholder group used the maps and impact analyses in conjunction with other data sets to iteratively identify economic and ecological trade-offs in designations of different areas as MPAs at regional, port, and fishery extents. Their final proposed MPA network designated 20% of state waters as MPAs. Potential net economic loss ranged from 1.7% to 14.2% in the first round of network design and totaled 6.3% in the final round of design. This process is a case study in the application of spatial analysis to validate and integrate local stakeholder knowledge in marine planning.

Asymmetrical quartz crystallographic fabrics formed during constrictional deformation

Numerical simulations predict unique quartz crystallographic fabric patterns for plane strain, flattening, and constriction. Multiple studies support the predictions for plane strain and flattening. To test predictions for constriction, this paper analyzes five examples of quartz crystallographic fabrics from a 1-km-wide domain of L tectonites in the Pigeon Point high-strain zone, Klamath Mountains, California, U.S.A. These samples were deformed under greenschist- to amphibolite-facies conditions. Quartz c-axis fabrics are similar to the predicted double-girdle fabrics except that amphibolite-facies samples exhibit c-axis maxima and are distinctly asymmetrical about the elongation lineations. Activation of different slip systems combined with small deviations from pure constriction account for the c-axis maxima, and noncoaxial flow accounts for the fabric asymmetry. The simple-shear component is randomly oriented in geographic coordinates throughout the domain of L tectonites. These data confirm that numerical simulations predict the quartz c-axis fabric geometry developed during constriction for some deformation conditions, and they confirm the quartz a-axis patterns predicted for constriction for the first time. These data also demonstrate that the relationship between quartz crystallographic fabrics and strain geometry is not straightforward, and they indicate that a-axis fabrics may be more useful indicators of strain geometry variations.

Kinematic significance of L tectonites in the footwall of a major terrane-bounding thrust fault, Klamath Mountains, California, USA

Detailed geologic mapping, cross-section reconstructions, strain analyses, and kinematic analyses, enable the reconstruction of a ∼one-kilometer-wide domain of L tectonites in the east–west-striking, subhorizontal to gently south-dipping Pigeon Point high-strain zone (PPHSZ) associated with a major thrust fault separating oceanic- and arc-affinity terranes in the Klamath Mountains, California. L tectonites are associated with: (1) a convex-upward warp of the upper high-strain-zone boundary, (2) a transition from mafic metavolcaniclastic rocks to micaceous quartzites, (3) folds subparallel with mineral lineations, (4) emplacement of synkinematic ultramafic/mafic intrusive bodies, and (5) a local temperature increase from greenschist- to amphibolite-facies conditions. Pure-shear-dominated deformation accommodated zone-normal shortening and transport-parallel elongation coupled with subordinate top-to-the-west-directed, thrust-style simple shear. L tectonite formation was controlled by the shape of the high-strain-zone boundary driving lateral flow into the apex of the lens-shaped zone in response to a favorable kinematic geometry and bulk strain in the constrictional field. Localized magmatic heating best explains the shape of the high-strain-zone boundary, but L tectonites are not partitioned into a single rheological domain. During terrane amalgamation strain-path partitioning occurred with localized top-to-the-west-directed simple shear partitioned into a structurally overlying thrust zone and pure-shear-dominated subvertical shortening and transport-parallel elongation partitioned into the PPHSZ.

Genetic evidence for the cryptic species pair, Lottia digitalis and Lottia austrodigitalis and microhabitat partitioning in sympatry

It has been proposed that the common West Coast limpet, Lottia digitalis, is actually the northern counterpart of a cryptic species duo including, Lottia austrodigitalis. Allele frequency differences between southern and northern populations at two polymorphic enzyme loci provided the basis for this claim. Due to lack of further evidence, L. austrodigitalis is still largely unrecognized in the literature. Seven additional enzyme loci were examined from populations in proposed zones of allopatry and sympatry to determine the existence of L. austrodigitalis as a sibling species to L. digitalis. Significant allele frequency differences were found at five enzyme loci between populations in Laguna Beach, southern California, and Bodega Bay, northern California; strongly supporting the existence of separate species. Both species exhibit two microhabitat morphotypes, a gooseneck barnacle morph in the mid-intertidal zone and a rock morph in the high-intertidal zone. In sympatry, L. austrodigitalis was more abundant higher in the intertidal on rocks, whereas L. digitalis was more abundant lower in the intertidal on barnacles. This finding supports earlier claims of microhabitat partitioning in this sibling species pair. In addition to this finding, the transition zone between the species was found to have shifted substantially northward in only two decades, from Monterey Peninsula, CA to near Pigeon Point, CA, where L. digitalis previously dominated.

A compaction correction for the paleomagnetism of the Cretaceous Pigeon Point Formation of California

The paleomagnetism of the Cretaceous Pigeon Point Formation turbidites was reexamined to determine whether the 25° of southerly paleolatitudinal offset originally observed (Champion et al., 1984) for these rocks was all, or in part, due to compaction shallowing of their paleomagnetic inclination. The study consisted of two parts: (1) A standard paleomagnetic study, including detailed thermal and alternating field demagnetization, was conducted on oriented cores collected at Pigeon Point, approximately 50 km south of San Francisco, California. The results of this study were combined with the alternating field demagnetized results for samples provided by D. Champion from the initial Pigeon Point paleomagnetic study. The combined data set has a mean direction for Pigeon Point (I=41.6°, D=346.9°) similar to that originally obtained by Champion et al. (1984). (2) Material from the Pigeon Point Formation was disaggregated, given a laboratory analog of a postdepositional remanence, and compacted to pressures as high as 0.13 MPa which caused volume losses up to 53%. The laboratory‐compacted samples were alternating field demagnetized, and their magnetic inclination and anisotropy of anhysteretic remanence were both measured. These data were used to derive correction curves, following Jackson et al. (1991), which describe the specific relationship between remanence anisotropy and inclination shallowing for the Pigeon Point Formation. Two correction curves were determined, one assuming that the magnetic particle orientation distribution experienced a prolate deformation after remanence acquisition and one assuming an oblate deformation. These two different corrections were necessary because the anisotropy of anhysteretic remanence indicates a composite fabric due to both a prelithification technically caused lineation and a burial compaction foliation. The anisotropy of anhysteretic remanence measured for each paleomagnetic sample and the correction curves determined from the laboratory compaction experiments indicate that the inclination of the Pigeon Point Formation has been shallowed by burial compaction. The compaction‐corrected Pigeon Point mean directions assuming either a prolate (I=53.1°, D=347.2°) or an oblate (I=49.8°, D=346.8°) deformation suggest only 13° to 16° of southerly paleolatitudinal offset for the Pigeon Point Formation in the Cretaceous, not the 25° originally observed (Champion et al., 1984). The resulting paleolatitude for the Pigeon Point Formation could indicate that Salinia served as a link between the cratonic Sierra Nevada arc to the north and the Peninsula Ranges/Baja‐Borderlands allochthon to the south. Alternatively, our results suggesting a 10° compaction inclination shallowing for the Pigeon Point turbidites may indicate that many of the paleomagnetic studies placing the Peninsula Ranges/Baja‐Borderlands 15° to the south of North America in the Cretaceous and Tertiary may have suffered from a similar effect and that the allochthon has been nearly in place since the Cretaceous.

Primary fabric ellipsoids in sandstones: implications for depositional processes and strain analysis

When measuring strains in deformed clastic rocks, geologists usually assume one or more of the following: (1) objects were initially circular; (2) objects were initially non-circular but had uniform orientations; (3) object populations initially had a fabric, but that this fabric had a symmetrical relationship to bedding; or that (4) initial fabrics are recognizable even after straining. To evaluate these assumptions, we measured 43 fabric ellipsoids in non-strained, poorly sorted sandstones from four depositional settings: DSDP core 174 (fan and abyssal plain deposits off the coast of Oregon); the Cretaceous Great Valley sequence, California (fore-arc deposits): the Cretaceous Pigeon Point Formation, California (accreted and slumped turbidites); and crossbedded sandstones from intracontinental basins in California and Australia. Our results indicate the following: (1) in two-dimensional cuts, individual grains have variable but usually small axial ratios (<3/1) and grains with larger axial ratios are more often, but not always, oriented at small angles to bedding; (2) averaged ratios and orientations of populations of grains in three dimensions define non-spherical fabric ellipsoids, but with small axial ratios (average principal ratios = 1.31:1.14:1); (3) these fabric ellipsoids show a wide range of shapes; and (4) orientations of fabric ellipsoid XY planes have highly variable orientations and are not parallel to bedding or cross-bedding. These results indicate that fabric ellipsoids measured in deformed sandstones must be corrected for the presence of primary fabrics when attempting to calculate strains. However, because of the variable orientations and shapes of the primary fabric ellipsoids and lack of relationship to bedding, strains can, at best, only be bracketed by multiplying final ellipsoids measured in strained samples by reciprocal primary fabric ellipsoids having a variety of orientations and shapes. These data and microstructures in grains and matrix cements also argue against significant compaction during burial in these clast-supported, sand-rich units and instead suggest that the primary fabrics largely reflect grain packing processes during deposition, and/or slumping and packing in the case of the Pigeon Point samples.

Pre-lithification structures, deformation mechanisms, and fabric ellipsoids in slumped turbidites from the Pigeon Point Formation, California

Paterson, S.R. and Tobisch, O.T. 1993. Pre-lithification structures, deformation mechanisms, and fabric ellipsoids in slumped turbidites from the Pigeon Point Formation, California. Tectonophysics, 222: 135–149. Quantitative fabric, structural, and microstructural analyses of pre-lithification folds, foliations, and lineations formed by slumping of turbidite sequences in the Cretaceous Pigeon Point Formation, California, provide a useful comparison with strain and microstructures developed in lithified and tectonically deformed turbidites. Our results indicate the following: 1. (1) multiple generations of folds, cleavages, and lineations can develop prior to any post-lithification tectonic deformation 2. (2) individual grains in sandstones have variable axial ratios, but the ratios and orientations of large populations of grains define fabric ellipsoids with small axial ratios ( ave. = 1.25:1.13:1) 3. (3) phyllosilicate grains define moderate flattening fabrics (reflecting 20–40% shortening or volume loss), with the intensity of alignment partly controlled by the percent of quartz and feldspar grains 4. (4) the fabric ellipsoids in sand-rich layers largely reflect deposition and slumping: pre- and post-slump compactions did not occur, in sand-rich units but did align clay particles in mud-siltstone units, and 5. (5) intra-grain microstructures in quartz and feldspar (e.g., undulose extinction, subgrains) are inherited or recycled features rather than representing effects of post-lithification strains. Our data also suggest that prelithification slumping occurred by pervasive grain rotation and grain boundary sliding in saturated sands with some local movement of material along bedding horizons. A likely model for the folding and associated fabrics is that buckling and fold-hinge flattening drove fluid expulsion, which in turn caused local grain-scale realignment, transposition of bedding, and the development of an axial planar cleavage in the hinge zones. Continued fluid flow was channeled by the clay-silt layers in fold limbs and axial plane cleavege in fold hinges.

Pebbly mudstones in the Cretaceous Pigeon Point Formation, western California: a study in the transitional stages from submarine slumps to cohesive debris flows

The pebbly mudstones in the Late Cretaceous Pigeon Point Formation originated by slumping and related debris-flow processes in a submarine canyon/slope depositional system. The sedimentary characteristics of the pebbly mudstones (PM) enable the distinction of two main varieties: (a) heterogeneous or “patchy” pebbly mudstones (PPM) exhibiting irregular bed geometries and diffuse to irregular bed contacts, with maximum clast sizes in intraformational boulder-sized population, including abundant rip-up mudstone and sandstone clasts with common soft sediment deformations; (b) homogeneous pebbly mudstones (HPM) with tabular bed geometries, non-erosive and almost flat bed contacts, maximum clast sizes in extraformational pebble-sized fraction and scarce to absent soft-sediment deformations.The two varieties of pebbly mudstone represent the mechanical transition from slumps to cohesive debris flows. The presence of abundant intraformational clasts and disrupted, yet preserved slump-fold features in the PPM suggest that this facies represents a stage closer to the slump end-member. As the shear-strain progressed and a fully remolded cohesive debris flow developed, an almost complete disaggregation of the poorly consolidated sand and mud clasts and the incorporation into the remolded “matrix” phase took place.

Allocation of organic material and energy to the holdfast, stipe, and fronds inPostelsia palmaeformis (Phaeophyta: Laminariales) on the California coast

Postelsia palmaeformis were collected from the lower intertidal at Pigeon Point, California, USA, in May 1987, and the proximate composition and allocation of energy to the various body components were determined. The holdfast and stipe have a proximate composition (% dry weight) of ca. 40% ash, 5.3% protein, 1% lipid, 2% soluble carbohydrate, and 55% insoluble carbohydrate. The fronds have a proximate composition of ca. 25% ash, 6.5% protein, 2% lipid, 3% soluble carbohydrate, and 65% insoluble carbohydrate. The energetic level was ca. 12 kJ g-1 dry wt and ca. 19 kJ g-1 ash-free dry wt. The relative proportion of three plant components varied, comprising 26, 39, and 35% wet wt and 20, 42, and 38% kJ for the holdfast, stipe, and fronds, respectively. A plant with a basal stipe diameter of 33 mm contains 114 g wet wt and 266 kJ. The maximal density found in May 1987 was 826 plants, 49 301 g wet wt, and 106 157 kJ m-2.P. palmaeformis differs in these characteristics from another intertidal pheophyte,Durvillaea antarctica, that is found in a high-energy intertidal zone.

Application of wind‐forced, long, coastal‐trapped wave theory along the California coast

The theory of wind‐forced, frictional, long, coastal‐trapped waves is applied along the California coast (1) to examine the sensitivity of the model to the numerous arbitrary and subjective choices which must be made during the application procedure and (2) to hindcast observable quantities in the region of the Coastal Ocean Dynamics Experiment (CODE) in an attempt to understand the dynamics of the region. Results of the model sensitivity study show that the model predictions are highly sensitive to the choice of wind stress used to force the model. Along the California coast, measured coastal and buoy winds are far superior to the calculated (Bakun) winds. The model predictions are relatively insensitive to uncertainties in the other model inputs. Hindcast results show that bottom pressure and alongshelf currents over the shelf are primarily wind forced throughout the year with most of the forcing located between Pigeon Point (∼200 km south of CODE) and the CODE site. While the time variability is hindcast quite well, the model systematically underpredicts the bottom pressure and alongshelf currents by a factor of 1.2–2.5 and fails to predict the observed midshelf vertical structure of the alongshelf currents. Cross‐shelf velocities and temperatures are poorly hindcast throughout.

Mytilophilus pacificae n. g., n. sp.: A New Mytilid Endocommensal Ciliate (Scuticociliatida)

Mytilophilus pacificae n. g., n. sp.: A New Mytilid Endocommensal Ciliate (Scuticociliatida)

Tectonic and eustatic controls of late quaternary shelf sedimentation along the Central California (Santa Cruz) continental margin: high-resolution seismic stratigraphic evidence

A high-resolution “uniboom”, seismic stratigraphic investigation of a portion of the central California continental shelf has demonstrated that depositional patterns and sequences are controlled largely by an interplay of glacioeustatic sea-level fluctuations superimposed on local tectonics. Wrench tectonics, associated with active right-lateral shear along the San Gregorio fault zone, and the Pigeon Point Basement High control the location, distribution and overall geometry of depositional sequences via en echelon folding and differential subsidence. Areas of relatively thick and thin late Quaternary sediments conform in large part with structures produced during wrenching. Glacioeustatic sea-level oscillations have also shaped depositional patterns and sequences. Correlation of our seismic stratigraphic data with a southern California continental margin sea-level curve, suggests that during the last glacial maximum, approximately 18,000 yrs ago, a relative lowstand resulted in the erosion of a distinct unconformity upon which late Quaternary sediments have accumulated. A rapid rise of sea level to a relative stillstand, approximately 12,000 yrs ago, produced a concave-up, marine terrace profile across the mid-shelf, that has since been infilled with as much as 22 m of Holocene clastic sediments. A relative drop of sea level, approximately 11,000 yrs ago, allowed sediments to build seaward as a series of prograding clinoforms that form the basal sequences of the late Quaternary sediment fill. The succeeding Holocene transgression partially eroded the top of this earlier regressive sequence, and has now established a typical, wave-graded shelf along which sediments fine in a seaward direction to water depths of 90–100 m. At greater shelf water depths, surface sediments coarsen and appear to be relicts of previous relative sea-level lowstands. The presence of now submerged and buried marine terraces along both the central and southern California continental margins, at elevations lower than modern terraces actively forming today, suggests that flights of raised marine terraces may not always decrease in age with decreasing elevation, as is commonly assumed for relative dating. Because sea-level fluctuations during at least the past 700,000 yrs, have been both numerous and of unequal magnitudes, it is likely that age inversions will occur within any given flight of raised Quaternary marine terraces along tectonically active continental margins.

Sudden Clarity at the Artichoke Stands, and: Small Hours

SUDDEN CLARITY AT THE ARTICHOKE STANDS / David Barber It is the bargain season along the highway where the usual muscular sky dismisses the shape of things to come. Five for a dollar. Six for a dollar. Eighteen cents a pound. The first serious tilt toward summer, the locals would tell you, begins in the earnestness of early artichoke stands: one after another blooming out of the mist, desperately generous, just before you pass. One obvious thing to say about artichokes is how sexual. All that opening, armor that tries to talk you out of it, the secret bud at the center speaking for everything forbidden. So much of it prelude. But even here where they tumble in the beds of pickups, spill over tables, stun the roadsides with their wantonness, it's no different than anywhere else: the emblems of desire resolve into the particular. I'm thinking of a checkered tablecloth, ringless hands, the slow cajoling of gas heat and a kitchen window hitched six inches to keep the spices honest. Scarves of steam; two artichokes perspiring on my mother's china. I'm thinking of a corner table in a beachfront cafe and the fingers of a woman who did not want anything I could give her undressing an artichoke with a deliberacy that seemed almost sad. The smallness of her wrists, teethmarks on the spent clutter of petals, the last lump of its heart in my own mouth:her quick gift, her gesture. And I'm losing myself, as the scale complains tunelessly beneath my dozen, over the ingenuity it must have taken to first see cuisine in the hard aloofness of these blossoms and over the artful lengths we will go for our three seconds of shuddering. It is absurd. It is always 18 · The Missouri Review absurd, passion, until we concede to the fine details of it: Chinese soap, half-moon scar above her left nipple, hole in the armpit of her favorite dress, Pigeon Point, Coltrane, blackberries; that alarming lavender sky in the Monet postcard pinned at perfect eye-level to one who is leaning close, looking up, riding her. David Barber The Missouri Review · 19 SMALL HOURS / David Barber The dark has everything to do with memory. Memory being what the dark of our bodies abides by. What swells without warning. Afterwards, she talked and he listened. It was the year of her birth. The melons were beautiful that summer and the heat tremendous. She likes the story best about her father pulling off the road to purchase a heroic watermelon that took two arms to carry though the contractions by that time were fierce. She likes the thought of newspapers spread on the tailgate all delivery long. The Rambler parked in the shade by the hospital. Her father slicing away. She got out of bed to close the window. Her body was darker than the rest of the room. Then he talked and she listened. He likes how inside the dark of melons there is light. The way it waits there. It calls to mind how light is dark's child. It reminds him of rooms made intentionally dark where his body got lighter and lighter. If love is dark work, it is only because the body beside us can be the light we live by. He doesn't like to call it hunger. It's more luminous than that. We press our breath into service like saws. Something opens and we see. 20 · The Missouri Review ...