Bay Of Campeche Research Articles

Nested reliability analysis of mooring lines for floating systems

A formulation for the nested reliability analysis of mooring lines is presented, which handles the uncertainty in the maximum dynamic line tensions that is assessed conditional on the uncertain environmental variables describing extreme sea states. The formulation is applied to calibration of partial safety factors for the ultimate limit state. Response surfaces are used to describe the mean line tension and the probability distribution parameters of the maximum dynamic tension as functions of the environmental variables. The appropriateness of using simplified formulations of the maximum dynamic tension in the limit state function is examined, as well as the effect of reducing the number of environmental variables that are treated as uncertain. Numerical results are given for mooring lines designed for FPSO systems at 500 m, 1000 m, and 1500 m water depths in the Bay of Campeche (Gulf of Mexico) using environmental models based on hurricane and storm hindcast data.

Deep Currents in the Bay of Campeche

Abstract Data from five moorings deployed in the Bay of Campeche during November 2007–July 2008 are used to analyze subinertial motions of waters below 1000-m depth. To the authors’ knowledge, this is the first time such a comprehensive observational program of direct deep-current measurements has been carried out in the region. The mean currents are in agreement with a cyclonic circulation at 1000-m depth; however, this cyclonic pattern is not so clearly defined at deeper levels. Only at the deepest mooring, located at 3500-m depth, are the mean currents uniform all the way to the bottom. Over the Bay of Campeche’s smooth western slope, currents show features compatible with topographic Rossby waves having vertical trapping scales thicker than 700 m, periods between 5 and 60 days, and horizontal wavelengths of 90–140 km. In contrast, the eastern slopes are characterized by rough topography, and motions with periods longer than 28 days decrease toward the bottom, suggesting a substantial reduction in the low-frequency topographic Rossby wave signal. Velocities from one of the two neighboring moorings located over the eastern rough slope have a strong 3-day period signal, which increases toward the bottom and has a vertical trapping scale of about 350 m. These higher frequency motions are interpreted in terms of edge waves.

Preliminary trials on the use of large outdoor tanks for the ongrowing of Octopus maya juveniles

AbstractOctopus mayahas high growth rates, direct embryo-nicdevelopmentandhighhatchlingsurvival,makingit a good candidate for aquaculture diversi¢cation.The present study was designed to evaluate growthrate,survivalandfoodconversionofO.mayajuvenilescultured in outdoor tanks. Octopuses were capturedfrom the wild during the ¢shing season, and fed dis-carded ¢sh heads and whole crabs.Three trials wereconducted between 23 and 32 days, in September(trial1),October(trial2)andNovember(trial3)wherea decrease in sea water temperature was registered(29^24 1C,fromSeptembertoNovemberrespectively).Octopuseswereheldinthreeoutdoortanksof5m 2 ofbottom area and 0.5m deep, aerated sea water andwater £ow allowing10% of water exchange per day.Initial density was between 2.9 and 3.8kgm 3 withdiierent initial mean weight of 542.3 18.8,493 11.9 and 321 7.8g, for trials 1, 2 and 3 re-spectively. Speci¢c growth rate varied between 1.8and 2.7%BWday 1 with no apparent relation withthe culture temperature. These results put in evi-dencethattanksusedareadequatefortheongrowingof O. maya juveniles, with commercial size being at-tainedinafewweeks.Keywords: cephalopods,culture,growthrate,foodconversion,Octopusmaya,outdoortanksIntroductionThestudyofOctopusspp.culturehasrecentlyunder-gone a signi¢cant increase throughout the world,particularly in Spain, Italy, Portugal and Greece(Vaz-pires, Seixas & Barbosa 2004; Iglesias, Sanchez,Bersano, Carrasco, Dhont, Fuentes, Linares, Mun oz,Okumura, Roo,Van Der Meeren,Vidal & Villanueva2007). The need for diversi¢cation, taking into con-sideration biological and economical aspects, makescephalopods in general and octopuses in particular,potentialcandidates for industrialculture.TheYucatanoctopus,OctopusMaya,isanendemicspeciesfromtheYucatanpeninsula,withdistributionranging from the Campeche bay, in the North of theYucatanpeninsula,toIslaMujeres(Solis1967).Lately,the range has beenwidened inthe Northern limit toCiudaddelCarmen,Campeche(Solis1997,1998).Thisspecies accepts dead prey or prepared diets immedi-atelyafterbeingborn,andeasilyadaptstolaboratoryconditions (Rosas,Tut, Baeza, SaŁnchez, Sosa, Pasc-ual,Arena,DominguesC Derusha, Forsythe, Dimarco & Hanlon1989; Solis1998; Domingues, Lo¤pez, Mun oz, Maldo-nado, Gaxiola & Rosas 2007; Rosas, Cuzon, Pascual,Gaxiola, Lo¤pez, Maldonado & Domingues 2007; Ro-sas,Tut, Baeza, SaŁnchez, Sosa, Pascual, Arena, Dom-ingues&Cuzon2008)upto four(Hanlon&Forsythe1985) or ¢ve (Van Heukelem1983) generations. Thisspecies has fast growth rates up to 8%BWday

Horizontal movements of Atlantic blue marlin (Makaira nigricans) in the Gulf of Mexico

We examined movements of Atlantic blue marlin (Makaira nigricans) from the Gulf of Mexico based upon 42 pop-up archival transmitting (PAT) tags. Long deployments (including one 334-day track) revealed diverse movement patterns within the Gulf of Mexico. North–south seasonal changes in blue marlin distribution showed strong correspondence with established seasonal patterns of sea surface temperature and primary production. During the summer spawning season, blue marlin utilized outer shelf and shelf edge waters in the northern Gulf of Mexico, and longer duration tracks indicated overwintering habitats in the Bay of Campeche. Egress occurred throughout the year and was difficult to determine because some tracks ended in the Straits of Florida (n = 3) while other tracks recorded movement through it or the Yucatan Channel (n = 4). Our results indicate that Atlantic blue marlin have a more restricted geographic range of habitats than previously recognized and that the Gulf of Mexico provides spatially dynamic suitable habitat that is utilized year-round through seasonal movements.

Crude Injustice in the Gulf: Why Categorical Exclusions for Deepwater Drilling in the Gulf of Mexico are Inconsistent with U.S. International Ocean Law and Policy

Those who cannot remember the past are condemned to repeat it. (1) I. INTRODUCTION II. HIGHSTAKES PROSPECTING IN A FRAGILE OCEAN. A. Overexploitation B. Pollution 1. Nutrient Loading 2. Synthetic Pollutants 3. Oil Pollution C. Climate Change and Ocean Acidification D. Deepwater Environments-The Last Frontier III. THE SEARCH FOR LIQUID GOLD; HIGH STAKES PROSPECTING IN THE GULF A. Gulf of Mexico: The Nation's Testing Ground B. Deepwater Horizon: Leaving a Legacy of Environmental Harms IV. NEPA AND OFFSHORE OIL PRODUCTION A. Council on Environmental Quality B. NEPA Compliance C. NEPA's Hard Look Requirement D. NEPA and Offshore Oil Drilling E. Deepwater Horizon-MMS Review of BP Plan 1. MMS: Environmental Review for BP Lease 2. Categorical Exclusion of BP's Exploration Plan V. Analysis and Recommendations A. Categorical Exclusions for Exploration Plans Violate NEPA and OCSLA 1. MMS: Failure to Assess the Impacts of a Catastrophic Oil Spill 2. MMS: Failure to Assess the Impacts of Using Dispersants in Deep Water 3. MMS: Categorical Exclusion of BP's Exploration Plan B. The Existing Environmental Review Process for Deepwater Drilling in the Gulf is Inconsistent with U.S. Ocean Policy C. Categorically Excluding Exploration Activities on the Outer Continental Shelf from Environmental Review Is Inconsistent with U.S. Obligations under International Law VI. CONCLUSION I. INTRODUCTION In an instant, oil and gas fumes raced from the well to the surface through the drill collar, exploding on contact with the semisubmersible oil rig's motors. Equipment designed to prevent such well blowouts failed, and oil flowed freely to the surface to fuel a massive fire that consumed the rig and caused it to collapse into the Gulf of Mexico. As the rig fell to the sea floor, the underlying well structure broke apart and allowed oil from the well to spew unimpeded into the ocean. Month after month the world watched in horror as tens of thousands of gallons of oil flowed into the Gulf's prime fishing grounds each day. Every effort to contain the oil failed. As some workers drilled relief wells to lower the pressure at the site of the blowout, others sprayed dispersants onto the growing oil slick to break down the oil before it reached the coast. Workers raced to implement measures to mitigate the environmental impact of the oil on beaches, inlets and estuaries. Politicians impatiently demanded accountability and financial commitments from responsible parties. Within days of the spill, the Gulf ecosystem revealed its fragility and vulnerability to human activity. White sand beaches turned black, seabirds lost their ability to fly, and marine organisms washed ashore dead--all victims of oil exposure. Technology proved inadequate to remove most of the oil from the water column. After millions of gallons of oil had been released into the Gulf, workers finally found a way to cap the well and stop the flow of oil, leaving the Gulf with a toxic legacy and an uncertain future. The account above bears a remarkably close resemblance to the April 20, 2010 Deepwater Horizon (DWH) oil well blowout that occurred off the coast of Louisiana, killed eleven people, and led to the largest oil spill in U.S. history. (2) Sadly, it is not. It is actually an account of the 1979 Ixtoc I oil well blowout in Mexico's Bay of Campeche that caused the release of approximately 147 million gallons of oil into the Gulf of Mexico (Gulf). (3) The oil contaminated 162 miles of Gulf shoreline, including large sections of the Texas coast. (4) The migration of oil from Mexican to U.S. waters caused a wide variety of damages to natural resources in the Gulf and caused economic hardship for many people who relied on the ocean to earn a living. …

Life on the Margins: (Ex) Buccaneers and Spanish Subjects on the Campeche Logwood Periphery, 1660-1716

In 1675, William Dampier set sail from Jamaica for the Bay of Campeche on Mexico's Yucatán coast to trade for logwood. Dampier, who would later become famous as a naturalist, a buccaneer, and one of the foremost chroniclers of the Golden Age of English buccaneering, recorded his experiences over the course of a year spent in English logwood communities near this Spanish settlement. The author's account gives a fascinating portrayal of a society beyond the margins of imperial control. In Laguna de Términos, an inlet just west of the town of Campeche (in Mexico's Yucatán Peninsula), English sailors cut logwood, a popular dyestuff used in Europe for red, purple, and black clothing dyes and ink, that grew throughout the swampy tropical lowlands of the area. They traded their harvest with merchants who would ship it to ports as far away as Boston, London, and Amsterdam. Seeking an independent life separate from the arbitrary power of shipboard hierarchy, the loggers lived communally. They worked, hunted, and drank on their own schedule.

Inertial Currents in the southern Gulf of Mexico

Current velocity data recorded from 1 March to 17 June 1997 at four stations in the Bay of Campeche, southern Gulf of Mexico, were used to describe inertial currents. Data were low-pass filtered using a Lanczos filter, and transformed to the frequency domain with the classical Fast Fourier Transform, rotary spectra, and the Morlet Wavelet Method. The strongest total currents developed in the eastern part of the bay, with a dominant east-west component. The predominant direction of the total current was parallel to the coast. The amplitude of tidal currents was small when compared with subtidal currents. During the sampling period several episodes of inertial currents were observed, some of which corresponded to those predicted by theory. Inertial currents in the lower layer were linked through large phase lags, revealing the baroclinic mode of the inertial currents. Spectral energy was concentrated in the low-frequency bands, corresponding to inertial and subinertial periods. The dominance of spectral energy at low frequencies reveals the influence of mesoscale cyclonic and small-scale anticyclonic eddies in the northeastern Bay of Campeche. These eddies are believed to be the origin of the inertial currents, since the inertial currents observed were unrelated to wind forcing.

Biogeochemical controls on authigenic carbonate formation at the Chapopote “asphalt volcano”, Bay of Campeche

The Campeche Knolls in the Bay of Campeche, southern Gulf of Mexico, were investigated through detailed seafloor mapping, ROV surveys, and sediment and pore water sampling. The knolls are elongated, submarine hills created by salt tectonics with a positive relief of up to 800 m above the surrounding seafloor. Several of the knolls are associated with sea-surface oil slicks identified from satellite data, indicating the presence of hydrocarbon seeps on the seafloor. One of the knolls, named “Chapopote”, was studied in detail during two international research expeditions (SO174/2 and M67/2) and is characterized by extensive hydrocarbon seepage including large asphalt flows, oil and gas seeps, and seafloor gas hydrate deposits. Chemosymbiotic biological communities and authigenic carbonate deposits are associated with the seeps and are the result of both biogeochemical turnover and the interaction between downward-diffusing seawater and hydrocarbon-rich pore fluids at shallow sediment depth. Authigenic carbonates are characterized by aragonite, exhibit a porous texture, and are cemented by a matrix of microsparitic to sparitic aragonite. Macropores of the carbonates were completely filled with liquid oil. Carbonate microfabrics include peloidal or clotted fabrics that may indicate the existence of microenvironments resulting from microbial metabolism. Banded/botryoidal aragonite cements line the intra- and bioclasts and incompletely fill the pore spaces. The stable carbon isotopic composition of authigenic aragonite varies between − 28.6‰ and − 17.9‰ (PDB), identifying oil oxidation as the primary source of carbon to the DIC pool, while lipid biomarker data demonstrate the concurrent existence of microbial communities responsible for anaerobic oxidation of methane (AOM). These observations indicate the presence of additional, AOM-independent reactions responsible for carbon sequestration at hydrocarbon seeps and demonstrate the complexity of biogeochemical processes at seep sites in the Gulf of Mexico basin. Oxygen isotope data of authigenic aragonite vary from + 2.5‰ to + 3.8‰ (PDB), indicating carbonate precipitation in slight disequilibrium with the surrounding pore fluids.

Post-nesting migrations of loggerhead sea turtles in the Gulf of Mexico: dispersal in highly dynamic conditions

This study is the first report of post-nesting migrations of loggerhead sea turtles (Caretta caretta) nesting in Sarasota County (Florida, USA), their most important rookery in the Gulf of Mexico (GOM). In total, 28 females (curved carapace length CCL between 82.2 and 112.0 cm) were satellite-tracked between May 2005 and December 2007. Post-nesting migrations were completed in 3–68 days (mean ± SD = 23 ± 16 days). Five different migration patterns were observed: six turtles remained in the vicinity of their nesting site while the other individuals moved either to the south-western part of the Florida Shelf (n = 9 turtles), the Northeast GOM (n = 2 turtles), the South GOM (Yucatan Shelf and Campeche Bay, Mexico, and Cuba; n = 5 turtles) or the Bahamas (n = 6 turtles). In average, turtles moved along rather straight routes over the continental shelf but showed more indirect paths in oceanic waters. Path analyses coupled with remote sensing oceanographic data suggest that most of long-distance migrants reached their intended foraging destinations but did not compensate for the deflecting action of ocean currents. While six out of seven small individuals (CCL < 90 cm) remained on the Florida Shelf, larger individuals showed various migration strategies, staying on the Florida Shelf or moving to long-distance foraging grounds. This study highlights the primary importance the Western Florida Shelf in the management of the Florida Nesting Subpopulation, as well as the need of multi-national effort to promote the conservation of the loggerhead turtle in the Western Atlantic.

Distribution of total organic carbon and total nitrogen in deep-sea sediments from the southwestern Gulf of Mexico

The temporal and spatial variations of total organic carbon (TOC) and nitrogen (TN) contents, and the carbon-nitrogen ratio in superficial sediments collected at 115 locations at depths between 1,025 and 3,795 m in the Gulf of Mexico during the SIGSBEE, PROMEBIO and DGoMB cruises are herein reported. The average TOC concentration was 0.9 ± 0.3%, the TN 0.12 ± 0.03% and the C/N ratio 8.0 ± 1.7. None of the typically hemipelagic sediment samples recorded any sulfur. In contrast, chemosynthetic sediment samples from the immediate area of the Chapopote asphalt volcano in the Campeche Bay (3,300 m deep) were significantly higher both in their TOC and TN values than hemipelagic samples, and were characterized by high sulfur contents with local variations associated with bathymetric features in the lower continental slope and the abyssal plain. This study shows that the elemental composition of the abyssal sediments is controlled by depth and follows a parabolic pattern for both TOC and TN. Average values for the continental slope were TOC = 0.8 ± 0.2%, TN = 0.11 ± 0.0 4% (n=39), and for the abyssal plain TOC = 1.0 ± 0.3%, TN = 0.12 ± 0.03% (n=44). The C/N ratio suggests that the organic matter in the superficial sediments has a mixed hemipelagic-terrigenous origin, and it depends on the distance from the coast. This is a major contrast to open-coast gradients where C/N ratios remain constant, and thus it is characteristic of a marginal sea. The bathymetry affects TOC and TN, causing significant differences among the physiographic regions. TOC and TN recorded in a long-term time series station in the abyssal plain displayed changes with time, showing alternating periods of high terrigenous and photoautotrophic input. This study provides evidence of the inter-yearly variability in the origin of the organic matter in the abyssal plain. TOC and TN decrease with depth in the sediment due to the changing sedimentation conditions.

Role of Near-Bottom Currents in the Distribution of Sediments within the Southern Bay of Campeche, Gulf of Mexico

Abstract The sediment distribution in the southern Bay of Campeche is mainly governed by wind-induced currents and mesoscale cyclonic eddies. An increase in sediment grain size toward the sea is attributed to the presence of a convergence zone that sorts the sediments from heavier to lighter. A small anticyclonic eddy near the coast leads to a concentration of sediments westward of the Grijalva-Usumacinta River. We combined current profiles and charts of the distribution of magnetic susceptibility within sediments with a hydrodynamic numerical model to elucidate the distribution of the major sedimentary units in the Southern Bay of Campeche, Gulf of Mexico. Acoustic Doppler current profiles and geostrophic velocity data were used to set the water velocity at the open boundaries of the applied numerical model. The model was forced by the dominant winds. Sediment on the southeastern side of the bay is dominated by carbonates because of a lack of river discharge and other systems that contribute terrigenous ...

Seasonal and interannual variability of cross-shelf transports of chlorophyll in the Gulf of Mexico

The seasonal and interannual variability of offshore cross-shelf transports of chlorophyll-rich waters in the Gulf of Mexico is studied using Level-3, monthly SeaWiFS data and monthly NCEP/NCAR-Reanalysis winds for the period September 1997–August 2007. Offshore cross-shelf transports of chlorophyll-rich waters have a seasonal cycle mainly modulated by the component of the wind field along the coast. These transports are basically located at three regions: southwest of the Texas–Louisiana (LATEX) Shelf, the southern Bay of Campeche, and southeast of the Mississippi River mouth. Southwest of the LATEX Shelf and in the southern Bay of Campeche, the confluence of seasonal along-coast currents, produced by the convergence of the seasonal along-coast wind stress component, induces offshore cross-shelf transport of chlorophyll-rich waters, with maximum values of chlorophyll- a concentration occurring at these locations during May and October–November, respectively. On the slope, southeast of the Mississippi River mouth, the seasonal maximum of chlorophyll- a concentration is observed in July due to the prevailing southwesterly winds during this month. A large fraction of the interannual variability of the offshore cross-shelf transports of chlorophyll-rich waters in the southern Bay of Campeche is explained by anomalies of the convergence of the along-coast wind stress component. On the southwestern LATEX Shelf, in addition to this process, cyclonic and anticyclonic eddies reaching this region may contribute to the interannual variability by shifting the location of the offshore cross-shelf transports.

New Species of Prodistomum Linton, 1910 (Digenea: Lepocreadiidae) From the Longtail Bass, Hemanthias leptus (Ginsburg, 1952) In The Bay of Campeche, Gulf of Mexico

Prodistomum lichtenfelsi n. sp. (Digenea: Lepocreadiidae) is described; it was obtained from the intestine of the longtail bass, Hemanthias leptus (Ginsburg), collected from the Bay of Campeche in the Gulf of Mexico. This is the first record of a parasite from this host. Prodistomum lichtenfelsi n. sp. is similar to P. hynnodi, P. menidiae, and P. waltairensis in that it possesses a prepharynx that is distinctly shorter (153 microm [110-210] long) than the combined length of the esophagus (163 microm [110-220] long) and the pseudoesophagus (137 microm [120-170] long), but it differs from them in having an excretory vesicle that extends into the forebody, a smooth ovary and testes, and vitellaria that extend to the posterior level of the esophagus. An updated key to the 12 nominal species within Prodistomum is given, and the diagnosis of the genus is emended to include species possessing a sinuous external seminal vesicle.

Three Dimensional Hydrodynamic Model with Multiquadtree Meshes

This study presents a three dimensional model for the transport of conservative contaminants, which can be used for bodies of water which are affected by winds and/or tides. The model solves the equation of mass transport, based on results obtained using a hydrodynamic model for shallow waters that works in a finite volume scheme and a type of hierarchical grid, called multiquadtree, which is adaptable to the bathymetry. To solve the vertical coordinates, the coordinate z is transformed into a sigma (s) coordinate, thus allowing the same number of layers in the vertical, regardless of depth. This hydrodynamic model is validated using two cases: a long wave propagated in a channel of variable width and bottom and wind action in a rectangular basin. Finally, the results obtained are presented for a hypothetical single port outfall in the bay of Campeche, Mexico. The model developed here is both quick and easy to use and is efficient when compared with models presented by other authors since it uses adaptable grids which allow detailed solutions to be obtained for areas of interest such as coastlines and the area around an outfall.

Reliability-based design criterion for TLP tendons

This paper presents a methodology to perform a Load and Resistance Factor Design (LRFD) criterion for the design of Tension Leg Platform (TLP) tendons in their intact condition. The proposed design criterion considers the Ultimate Limit State (ULS) for the tendon sections, expressed in terms of the expected value of the extreme Interaction Ratio (IR), considering long-term storm sea states, and takes into account the dynamic load effects interaction and the statistics of its associated extreme response. The partial safety factors are calibrated through a long-term reliability-based methodology for the storm environmental conditions in deep waters of the Campeche Bay, Mexico. Different target reliability values are considered in order to evaluate the effect of this key parameter on safety factors. The results show that the partial safety factors reflect both the uncertainty content and the importance of the random variables in structural reliability analysis. When tendons are designed according to the developed LRFD criterion, a less scattered variation of reliability indexes is obtained for different tendon sections across a single or a variety of TLP designs. Finally, it is observed that the target reliability value has a strong influence over the safety factor values and thus over the final size of the structural elements.

Ek-Balam field: A structure related to multiple stages of salt tectonics and extension

The Ek-Balam field is a major oil and gas field in the offshore Campeche Bay, Mexico. The structure was formed as a result of multiple episodes of salt tectonics and associated extension. Salt movement into the core of the structure initiated in the Jurassic–Early Cretaceous and continued until the Miocene. The most prominent normal faults are of Jurassic–Early Cretaceous age and detach in the Jurassic salt. These faults mostly dip to the west, although in the vicinity of the Ek-Balam structure, some east-dipping faults are also present. Some of these faults were subsequently reactivated in the Late Cretaceous and Tertiary. Separating the Ek and Balam structures is a set of Upper Cretaceous faults, which drop the eastern part of the structure down. Tertiary faults are related to continued uplift of the salt and are symmetrically distributed with respect to the central uplift. Seismic time maps, three-dimensional depth models of the top of the Cretaceous breccia and the Kimmeridgian, and balanced structural cross sections provide accurate details of the structural geometry and fault patterns in the Ek-Balam structure. At the level of the Cretaceous breccia, many of the faults have small throws and are discontinuous along trend. The top of the Kimmeridgian, however, is cut by faults of different ages, many of which have significant throw and extend for longer distances. The detailed structural geometry and fault patterns will be useful for identifying compartments within the Ek-Balam field and for identifying secondary traps within Kimmeridgian and Oxfordian reservoirs.

Structural reliability evaluation considering capacity degradation over time

Due to the ageing of the existing infrastructure on a worldwide scale and to the lack of codes for the continued safety management of structures during their lifetime, it is necessary to develop mathematical tools to evaluate their structural reliability over a time interval taking into consideration the reduction in their structural capacities. In this paper, an approach to evaluating structural reliability that takes into account capacity degradation over time by means of closed mathematical expressions is proposed. Two alternative indicators of structural reliability are considered: (1) The expected number of failures over a time interval, taking into account the uncertainty due to both aleatory and epistemic uncertainties; (2) The confidence factor, λ conf ( t ) , and the confidence level, K x ( t ) , as functions of time ( t ) are presented within a Demand-and-Capacity-Factor Design format (as used in FEMA 351). Both indicators are extended (based on the approach proposed by Cornell and collaborators) to estimate the reliability of a structure over a time interval. This reliability analysis takes into account events of different intensities (all possible events at the site) by means of environmental hazard curves. It is assumed that the structural capacity decreases linearly with time. The proposed expressions can be applied to different types of structures and can consider different conditions and levels of cumulative damage. An illustrative example is presented using a simplified model of a fixed steel jacket platform located at Campeche Bay in the Gulf of Mexico. The damage condition considered is the fatigue crack sizes at the critical joints caused by service and storm waves. The environmental hazard is represented in this example by means of exceedance rate curves of the maximum wave heights. The results obtained from the proposed expression are analyzed and compared with those obtained from numerical integration.

Structural geometry and evolution of the Ku, Zaap, and Maloob structures, Campeche Bay, Mexico

The Ku, Zaap, and Maloob structures consist of an arcuate series of fold-thrust structures, which change orientation from approximately east-west to north-northwest–south-southeast along a structural salient in the offshore Campeche Bay, Mexico. The structures are related to a series of thrust faults, which merge into the Maloob thrust. The Ku, Zaap, and Maloob fields located on these structures together constitute an important complex of fields with proven remaining reserves of approximately 1850 MMBOE. The structures formed during three main periods of deformation: (1) a Jurassic–Cretaceous extensional episode; (2) a Miocene compressive phase, during which the main trap-forming structures were formed; and (3) a Pliocene to Holocene extensional episode, resulting in several listric growth faults. Three-dimensional (3-D) models of the main reservoir unit (Upper Cretaceous breccia), and other prospective reservoir units (Eocene and Kimmeridgian) constructed by integrating 3-D seismic interpretation, well data, and a series of balanced structural cross sections, provide an understanding of the geometry and evolution of the structures. The Zaap, Maloob, and sub-Maloob structures are interpreted as a series of faulted detachment folds, detaching within salt and other Jurassic ductile units. The front limbs of these structures are typically cut by thrust faults with small displacements, terminating in the lower Tertiary section. The Ku and Pakal structures also originated as a detachment fold, but was faulted relatively early in its deformational history. The frontal zone of this structure is marked by a closely spaced thrust system consisting of the Ku, Pakal-1, and Maloob thrusts. The 3-D models provide an accurate picture of the structural geometry of the principal reservoir units, which will be useful for future production from the fields and for exploration in adjacent areas in the basin.

Updated checklist and identification of areas of endemism of benthic amphipods (Caprellidea and Gammaridea) from offshore habitats in the SW Gulf of Mexico

An updated checklist of the benthic amphipods associated with soft bottoms in the SW Gulf of Mexico has been made and the areas of endemism have been identified. Amphipods were collected in a depth interval of 25 to 3700 m during six cruises from 1994 to 1999. A total number of 56 species were identified, 11 belonging to the suborder Caprellidea and 45 to the suborder Gammaridea. Thirteen species extended their geographical distribution within the Gulf of Mexico and four species were considered new records in the Gulf of Mexico. A biogeographic analysis based on the shared species and the parsimony criterion helped identify three areas of endemism in the SW Gulf of Mexico. They were named: area A, a small area on the continental shelf of the Bay of Campeche; area B, the continental slope of the Bay of Campeche; and area C, the lower continental slope of the Mexican ridges extending into the western Sigsbee abyssal plain. These areas are defined in terms of their complex topography that may help isolate habitats that promote endemicity.

Application of 129I / 127I to define the source of hydrocarbons of the Pol-Chuc, Abkatún and Taratunich–Batab oil reservoirs, Bay of Campeche, southern Mexico

Homogeneous 129I / 127I ratios from 6.51 ± 1.36 × 10 − 14 to 12.6 ± 1.49 × 10 − 14 were measured in formation brine at the Pol-Chuc, Abkatún, Taratunich–Batab off-shore oil reservoirs, Bay of Campeche in S-Mexico. Cosmogenic production could account for a homogeneous, Late Cretaceous/Paleocene time period (71.3 ± 5.3 to 56.3 ± 2.9 Ma) for the sedimentation and burial of organic material in the source formation. As the actual reservoir column is formed by Paleocene to Kimmeridgian sediments, the lower part of the lithological column must have received hydrocarbons that migrated downward from an initial source rock (Upper Cretaceous?) during a post-Paleocene event, probably during Miocene. Cosmogenic production from Tithonian shales can be excluded, as 129I would have been decayed. As an alternative or complementary process, the subsurface, radiogenic production of 129I / 127I by 238U-fission in Uranium-enriched sediments should also be considered to explain the present, low 129I / 127I ratios.