Younger Marine Research Articles

Risky Alcohol Use, Age at Onset of Drinking, and Adverse Childhood Experiences in Young Men Entering the US Marine Corps

To examine how childhood experiences relate to risky underage drinking. A survey study of men starting military training between June 11, 2002, and April 5, 2006. Multivariate logistic regression models compared risky drinkers with "all others" or with nonrisky drinkers; excluding nondrinkers. Marine Corps Recruit Depot, San Diego, Calif. Forty-one thousand four hundred eighty-two men aged 18 to 20 years. Main Exposures Age at drinking onset; childhood emotional, physical, and sexual abuse; childhood emotional and physical neglect; and household alcohol abuse, mental illness, domestic violence, or divorce. Risky drinking identified by scoring responses to 3 questions about alcohol consumption. Of 41,482 young men, 6128 (14.8%) were identified as risky drinkers, 18,693 (45.1%) as nonrisky drinkers, and 16 661 (40.2%) as nondrinkers. Among drinkers, early initiation of alcohol use was strongly associated with risky drinking, with a 5.5-fold risk if age at onset of drinking was 13 years or younger. Other associated factors included tobacco use, rural or small hometown, higher education, motivation to join the military for travel or adventure or to leave problems at home, numerous close friends and relatives, household alcohol abuse or mental illness, and childhood sexual or emotional abuse. When the comparison group included nondrinkers, additional associated factors included childhood physical abuse and domestic violence. These analyses confirm previous findings on risks for alcohol misuse in young adults and quantify these risks in new, large, multivariable models, adding unique perspective from a population of young Marines. Public health efforts to decrease alcohol misuse may be effectively targeted by prevention of underage alcohol use, tobacco use, and childhood abuse.

Moving hotspots or reorganized plates?

Hotspot fixity and no major plate reorganization in the past ∼40 m.y. are two propositions important for studying absolute plate motion and mantle dynamics. Reexamining the hotspot data with the NUVEL-1A relative plate motion model, we find that these two propositions cannot be simultaneously tenable: either hotspots have been moving relative to each other, or a major reorganization of plate motion occurred in the past ∼40 m.y. Statistical compatibility tests show that hotspot rate data are incompatible with trend data, implying that hotspots have moved. Furthermore, hotspot rates are consistently lower than those predicted by best-fitting absolute plate motion models. This may be explained by hotspots moving systematically opposite to the plate motion. If so, the moving hotspots still provide a useful reference frame for defining absolute plate motion. However, all hotspot trend data, with ages as old as 40 Ma, are statistically compatible, indicating no major reorganization of plate motion in the past ∼40 m.y. In this case, relative plate motion models based on young marine magnetic anomalies may be used to infer older (<40 Ma) plate kinematics, which lack direct constraints.

A Sound Approach to Soft Sediment Resolution

The last few years has seen a surge in research activities directed towards investigating properties and dynamics of young marine, limnic and fluvial sediments. It is by now a well established fact that the sequence of sediments ranging from concentrated benthic suspension over fluid mud to un-consolidated material summarized as liquid sediments (LS), act as carriers for a wide range of pollutants discharged or migrated into waterways. Knowledge of the transport and fate of LS allows determining the transport and fate of adsorbed constituents (e.g., heavy metals, pesticides, PCBs, PAHs). To assess the environmental impact of LS, efforts have to be made to better understand the processes in relation to hydrodynamics and the chemical and physical properties of the layers. Since physical laws limit the resolution and detection power of conventional seismo-acoustic systems in respect of LS, alternative measurement, data analysis and processing approaches have to be found. Adapted acoustic procedures initially developed for shallow water marine environments to extreme shallow water regimes using matched field inversion techniques can reveal geoacoustic parameters including density, compressional wave speed and attenuation as a function of depth and time. The paper outlines the effects of sediment mobility upon the environment followed by a short overview of techniques commonly used to investigate sediments and other freshwater/marine events. The problems faced and limitations of existing systems are briefly outlined. Results obtained with recently developed and refined geoacoustic inversion methods are presented highlighting their potential for long-term study of physical properties and dynamics of LS.

Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes

Oceania supplies ∼40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives ∼4 Mt yr−1 particulate terrestrial organic carbon with initial particle Corg loading ∼0.7 mg m−2. Corg loading is reduced to ∼0.3 mg m−2 in the topset-upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus, and high net sediment accumulation rates of 1–4 cm yr−1. Carbon isotopic analyses (δ13C, Δ14C) of ΣCO2 and Corg demonstrate rapid (<100 yr) remineralization of both terrestrial (δ13C <−28.6) and marine Corg (δ13C ∼−20.5) ranging in average age from modern (bomb) (Δ14C ∼60) to ∼1000 yr (Δ14C ∼−140). Efficient and rapid remineralization in the topset-upper foreset zone is promoted by frequent physical reworking, bioturbation, exposure, and reoxidation of deposits. The seafloor in these regions, particularly <20 m, apparently functions as a periodically mixed, suboxic batch reactor dominated by microbial biomass. Although terrestrial sources can be the primary metabolic substrates at inshore sites, relatively young marine Corg often preferentially dominates pore water ΣCO2 relative to bulk Corg in the upper foreset. Thus a small quantity of young, rapidly recycled marine organic material is often superimposed on a generally older, less reactive terrestrial background. Whereas the pore water ΣCO2 reflects both rapidly cycled marine and terrestrial sources, terrestrial material dominates the slower overall net loss of Corg from particles in the topset-upper foreset zone (i.e. recycled marine Corg leaves little residue). Preferential utilization of Corg subpools and diagenetic fractionation of C isotopes supports the reactive continuum model as a conceptual basis for net decomposition kinetics. Early diagenetic fractionation of C isotopes relative to the bulk sedimentary Corg composition can produce changes in 14C activity independent of radioactive decay. In the Gulf of Papua topset-upper foreset, Δ14C of pore water ΣCO2 averaged ∼ 300‰ greater than Corg sediment between ∼1–3 m depth in deposits. Diagenetic fractionation and decomposition aging of sedimentary Corg compromises simple application of 14C for determination of sediment accumulation rates in diagenetically reactive deposits.

War, Critical Thinking, and Self-Understanding

Ms. Noddings believes we should not gloss over the controversial aspects of issues such as but should challenge our students to confront them, grapple with them, and arrive at their own conclusions. CAN STUDENTS learn to think critically if they are not asked to engage with critical issues? Fostering critical thinking is frequently stated as a fundamental aim of education,1 and yet many teachers report that they have been forbidden to discuss such critical issues as current wars, religion, and cultural differences in styles of parenting. Critical thinkers raise questions about claims and about the motives of those who make them, they identify logical flaws in arguments, they evaluate the premises from which arguments are launched, they search for evidence to support claims, and they explore the likely consequences of proposed actions. Critical thinkers are also reflective in the important sense that they regularly turn their analyses and questions on their own thinking and practices. Thus critical thinking, as I am using the term here, addresses issues that are significant in the lives of those who engage in the practice. Moreover, teachers may need to help students come to understand that certain issues they have not yet considered are indeed significant in their lives. The study of formal and informal logic, reflection on past events, and simulation of conflicts all contribute to the development of critical thinking.2 But the failure to confront issues critical to the present lives of students when we seek to teach critical thought sends a contradictory message: think critically -- but not about really controversial issues! Or do it on your own time! School is not the place for analysis and discussion of critical issues. As a result, students who end their formal schooling with high school may never encounter important and fascinating debates on war, religion, or parenting. And they may or may not learn to think critically. Here I wish to present possible topics for a critical exploration of just one of these issues: war. War is already a major strand in the social studies curriculum, but the discussion is usually confined to political causes, leaders, battles, and the resulting rearrangement of national boundaries. I wish to address psychological issues related to that should concern all citizens, especially the young who might join the military right out of high school. The main question I address is this: How can critical thinking help us to understand ourselves better and come to terms with our attitudes toward war? The Attractions of War No one wants war was a claim heard repeatedly as the U.S. and Great Britain prepared to invade Iraq. Were the political leaders who said this lying, or were they trying to reassure their citizens that they did not want and would avoid it if at all possible? This question seems to be unanswerable, so I'll set it aside. Let's also set aside the obvious fact that some people make a great deal of money from and its aftermath, and, although they deny it, they do want war. The questions that we must help young people to explore are these: Are there people, other than the greedy, who want war? Why? Are you such a person? Anthony Swofford, a young marine, has written about the desperate attractions of war. He notes that stories and films that disgust Mr. and Mrs. Johnson in Omaha or San Francisco or Manhattan -- films that threaten to convert many of us to pacifism -- have a very different effect on military men. Swofford writes: [They] watch the same films and are excited by them, because the magic brutality of the films celebrates the terrible and despicable beauty of their fighting skills. Fight, rape, war, pillage, burn. Filmic images of death and carnage are pornography for the military man.3 The rest of Swofford's paragraph is too obscene to reprint here, but his story is a familiar one. …

Sources of osmium to the modern oceans: new evidence from the 190Pt-186Os system

High precision Os isotope analysis of young marine manganese nodules indicate that whereas the composition of modern seawater is radiogenic with respect to 187 Os/ 188 Os, it has 186 Os/ 188 Os that is within uncertainty of the chondritic value. Marine Mn nodule compositions thus indicate that the average continental source of Os to modern seawater had long-term high Re/Os compared to Pt/Os. Analyses of loess and freshwater Mn nodules support existing evidence that average upper continental crust (UCC) has resolvably suprachondritic 186 Os/ 188 Os, as well as radiogenic 187 Os/ 188 Os. Modeling the composition of seawater as a two-component mixture of oceanic/cosmic Os with chondritic Os compositions and continentally-derived Os demonstrates that, insofar as estimates for the composition of average UCC are accurate, congruently weathered average UCC cannot be the sole continental source of Os to seawater. Our analysis of four Cambrian black shales confirm that organic-rich sediments can have 187 Os/ 188 Os ratios that are much higher than average UCC, but 186 Os/ 188 Os compositions that are generally between those of chondrites and average-UCC. Preferential weathering of black shales can result in dissolved Os discharged to the ocean basins that has a much lower 186 Os/ 188 Os than does average upper crust. Modeling the available data demonstrates that augmentation of estimated average UCC compositions with less than 0.1% additional black shale and 1.4% additional ultramafic rock can produce a continental end-member Os isotopic composition that satisfies the requirements imposed by the marine Mn nodule data. The interplay of these two sources provides a mechanism by which the 187 Os/ 188 Os of seawater can change as sources and weathering conditions change, yet seawater 186 Os/ 188 Os varies only minimally.

Direct measurement of magnetic reversal polarity boundaries in a cross‐section of oceanic crust

Magnetic field measurements made by submersible define the cross‐sectional geometry of a magnetic polarity reversal boundary and the vertical variation of crustal magnetization in upper oceanic crust. Measured polarity boundaries show a systematic pattern of shallow dip towards the spreading axis within the upper extrusive lavas, and steeper dip in the lower extrusive lavas. This geometry is a consequence of the emplacement of extrusive lava at a midocean ridge. Reversal boundary geometry and magnetization estimates are used to calculate the magnetic contribution of the extrusive lava sequence to the overlying marine magnetic anomaly signal. From the forward modeling, the highly magnetized extrusive lavas contribute the majority (50–75%) of the observed sea surface magnetic anomaly, consistent with the extrusive crust forming the primary source layer for young marine magnetic anomalies.

Sources and Resources: The Catholic Imagination of Flannery O'Connor

Sally Fitzgerald Sources and Resources: The Catholic Imagination of Flannery O'Connor The subject of Flannery O'Connor's Catholic imagination is obviously a large enough challenge in itself,but as though that were not enough, when I first proposed to write sometiiing on die subject I proceeded to compound die problem by prematurely attaching an extravagant title to my as yet unwritten remarks—one that implicitly promised to touch upon not only its more or less direct sources, but on die developmental resources by which diat genial imagination was nurtured and instructed. By describing it as genial, I don't mean to suggest tiiat Flannery O'Connor's imagination was entirely affable, mild, or sunny. I use the word here in its fourth dictionary meaning (its primary meaning in the Italian language, which keeps closer to the meaning of the Latin root): that is, as touched, or marked, by genius—which is to say tiiat, by Benedetto Croce's definition, hers was a truly human imagination. The excerpts from O'Connor's notebooks are exclusive to diis issue of Logos. Quotations from them are strictly prohibited. Logos 1:1 1997 The Catholic Imagination of Flannery O'Connor It was sheer hubris in me, I now see, to dunk tiiat I could cover so muchgroundin a single paper. Suchan overreachtowarddioroughness did lead me, however, in die first instance, into closer consideration of material recentiy made accessible to me, andnotyetpublished in any of its parts. I knew the documents to be extremely important in diemselves ,but had not yet realized how much direct light diey would shed on die struggles ofan extraordinary young woman in her attempt not only to formulate a reliable understanding ofherselfjôr herself, and to gain an increasingly solid footing in her faith, but to comprehend (despite persistentself-doubt) a steadilygrowingsense ofdienature and demands of her unmistakable gifts, which seemed to be directing her firmlyto a closelyrelatedliteraryvocation. Inher case,shewasbrought to recognize a vocation in which all three components—die personal, die religious, and die literary—were not only inextricably bound togedier and interactive but were in tiiemselves profoundly Catiiolic, not only by reason ofa lifelongpersonal and religious formation, butby her own will and intent, and ensuing deep commitment to excellence in all tiiree areas, as she approached and reached aduldiood. Early glimpses, provided by herself in her own scrawl, of Flannery O'Connor in two different stages ofemerging self-awareness and growth are to be found in two ordinary school notebooks, mottled black and white, in which she put down her tiioughts. Not for publication, but for her own consideration and re-consideration. The first was written when she was an eighteen-year-old undergraduate at die College in Milledgeville, still living at home with her mother and extended family.Apparently she intended to keep such a record thenceforth, but tiiis first resolve seems to have lasted only a little over a month (celebrated as an "anniversary"when she had persevered even diat long). She is still clearly a schoolgirl, a little worried about her looks, her lack of social ease, and what otiier people tiiink of her, but grown-up enough to be reassured by die pleasure and satisfaction she finds in what she can do well, and by a sense of essential ^vulnerability to emotional derailment. She daydreams 79 80 Logos aloud of fame, of die independence she would like to win for her motiier and herself, ofriches, and ofeventual love. But for every adolescent fantasy, there is a countering glimpse of an evolving O'Connor more familiar to us, who supplies an antidote ofcool realism to delusions, great or small, by an astringent analysis of herself and of her truest sentiments and aspirations, within the universal context ofwhich she never at any point lost sight. At die same time, impatience with herself and laments over her own perceived shortcomings ofpersonality and performance are opposedby a sometimes astonishing self-regard,inwhich she frankly declares tiiather love for herself, and for her motiier, supersedes any odier she might lose—as she is about to lose, to a wartime reassignment, the companionship and reassuring admiration ofthe young Marine for whom she admits, in diese self-examinations...

In Search of Al Schmid: War Hero, Blinded Veteran, Everyman

During an intense firefight at the Tenaru River on Guadalcanal in August of 1942, Marine Private Al Schmid, a Philadelphia metal worker, shared a machine gun emplacement with two other young Marines: Johnny Rivers, a Native-American from rural Pennsylvania, and Lee Diamond, a Jew from Brooklyn. During many hours of night combat, as wave after wave of Japanese tried unsuccessfully to cross the Tenaru and overwhelm the thin line of American defenders, first Rivers was shot and instantly killed, and then Diamond was severely wounded. Furious over the death of his friend and fighting for his life, Schmid continued to try to ward off the enemy. Toward the end of the battle, which was to prove decisive for securing Guadalcanal, he was wounded by a grenade fragment. One of his eyes was immediately destroyed and the other was greatly damaged. Now sightless, Schmid continued, with what little aid the barely conscious Diamond could provide, to fire the machine gun. Eventually he was credited with killing two hundred Japanese before his position was relieved in the morning. Schmid spent much of the next two years in military hospitals, where unsuccessful efforts were made to save what little sight remained to him, and where he began the process of blind rehabilitation.

Actinoptychus splendens (Shadbolt) Ralfs (Bacillariophyceae): a biostratigraphic marker for the later part of the Holocene coastal deposits along the southern North Sea

Actinoptychus splendens is a conspicuous and widely distributed marine diatom. At present it is common in the coastal waters of the southern North Sea, but it appears to be absent in the older Holocene deposits along the Dutch and Belgian coasts. Its first postglacial appearance here can be dated at between 4400 and 4100 BP. By 3800 BP it is well established in the region. Although generally not abundant, it can be found in nearly every sample of younger marine or brackish deposits. The large amount of material investigated from the area, as well as the high preservation potential and easy recognition of the species, preclude any other explanation for its apparent absence along southern North Sea shores prior to ±4100 BP, than a late natural immigration. This appears to be quite exceptional, all the common species which generally occur in association with A. splendens being present from the onset of Holocene sedimentation. A. splendens may become an important marker taxon in the Holocene stratigraphy of the coastal plains along the southern North sea.

Long-chain aliphatic nitriles in pyrolysates of young kerogen: implications for the intermediates in petroleum hydrocarbon formation.

Gas chromatographic/mass spectrometric examination of products from laboratory thermal degradation of kerogen from a young marine sediment (Tanner Basin off California), revealed a series of long-chain nitriles whose carbon-chain lengths range from 12 to 26. These compounds appeared after the relatively mild thermal conditions of 310–350°C for 5–116 hrs and disappeared before major n-alkane generation. We hypothesise that n-alkanes are generated at the expense of long-chain fatty nitriles which in turn are formed via fatty acid amide-linked structures in kerogen. Heating of standard long chain (C18) fatty acid amides with kerogen produced n-alkanes with no odd/even predominance. The heating experiments showed that these nitrogen compounds have a strong potential for producing a series of normal hydrocarbons. Consequently, nitrogen-linked long-methylene-chain structures in kerogen analogous to fatty acid amides/fatty nitriles can act as one of the precursors of petroleum hydrocarbons.

On the presence of regular periodicities in the thermoluminescence profile of a recent sea sediment core

We briefly discuss how the thermoluminescence (TL) profile of a young marine sediment provides phenomenological information on the changes in the environmental conditions in the past 18 centuries. The main periodicities present in the TL profile are studied and the similarities between the TL variations and the fluctuations in the contemporary tree-ring A 14 C signal are considered. An interesting result is the presence, in the TL data, of a well-defined 11-year cycle which is stable and ‘in phase’ for the entire period analysed. We also discuss how four dominant periodicities present in the TL data may be rewritten as the sum of an 11.4-year and of an 82.6- year cycle (reminiscent respectively of the Schwabe and of the Gleissberg cycles of solar activity), which are both amplitude modulated by a 206-year wave. This last periodicity has already been shown to play a dominant role in the A 14 C record. These results suggest that the TL profiles of recent marine sediments may be successfully used as a new line of evidence for solar variability in the past centuries.

Integrated Geologic and Geophysical Mapping: An Example from the Muddy Sandstone Wind River Basin, Wyoming: ABSTRACT

Muddy Sandstone stratigraphic traps have been the primary stratigraphic exploration target in the Wind River basin (WRB) for BP Exploration and many in industry since the discovery of the Grieve field (30 MMBO, 60 bcf of gas) in 1954. Since 1984 in the eastern WRB, 18 wildcats have been drilled resulting in three new field discoveries which total approximately 23 MMBOE. BP Exploration staff has successfully predicted the reservoir outcome of over 95% of the wildcats by incorporating log facies and facies models with seismic amplitude mapping of the Muddy reflector. The Early Cretaceous Muddy Sandstone unconformably overlies the earlier Cretaceous marine Thermopolis Shale and is conformably overlain by the marine Mowry Shale. An incised valley system was cut into the Thermopolis Shale during a eustatic sea level drop. During the ensuing sea level rise in the southeast portion of the WRB, the Recluse sandstone is the primary Muddy reservoir unit. Secondary Muddy sandstone deposition of marine shoreline sandstones occurred during fluctuations of the primary eustatic sea level cycle. Therefore, in certain areas of the WRB , the Recluse member sandstones can be overlain and/or underlain by marine sandstones. In areas where the older and younger marine sandstones are absent,more » seismic amplitude mapping, incorporating well control, provides a method of mapping the extent of the valley fill sediments. The Muddy valley-fill sediments are generally less than 30 m thick and are encased in slower velocity shales. When valley-fill sediments are present, the Muddy reflector is high amplitude in contrast to low amplitudes when the valley-fill is absent. Estimates of valley fill lithology are provided through synthetic modeling of well logs representing different lithofacies. The resulting wavelet characterization, which includes wavelet shape and peak-to-trough time separation, improves predictability of sandstone distribution.« less

History of stage 5 sea level in Bermuda: Review with new evidence of a brief rise to present sea level during Substage 5a

Abstract Oxygen-isotope Substage 5e is represented by the Devonshire Formation in Bermuda. The occurrence of these coastal-marine deposits to about 5 m indicates Pleistocene sea-level data in Bermuda do not need tectonic corrections. A few published U-series coral dates suggest that a conglomerate (Spencer's Point Formation) may have formed during Substage 5c. Geologic mapping, however, indicates that the eolianite beneath the conglomerate is pre- rather than post-Devonshire Formation in age as was previously thought, and the aminostratigraphy of marine sheels also confirms the correlation of the Spencer's Point and Devonshire Formations. Substages 5c and 5a are represented by the Southampton Formation. Large eolianites comprise the bulk of this formation. They are onlapped by a few, small, younger marine (+1 m) and eolian deposits. Aminostratigraphy confirms that these late Southampton age deposits are significantly younger than the Devonshire Formation, and U-series dates indicate a Substage 5a age. The setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms. This evidence that sea level in Bermuda was at about present datum late in Substage 5a agrees with interpretations of Neotyrrhenian deposits of Mediterranean shorelines, but not with inferences from the deep-sea oxygen-isotope record, or with data from uplifted coral reefs.

Sm-Nd in marine carbonates and phosphates: Implications for Nd isotopes in seawater and crustal ages

This study explores the possibility of establishing Nd isotopic variations in seawater over geologic time. Calcite, aragonite and apatite are examined as possible phases recording seawater values of ϵ_(Nd). Modern, biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have Nd concentrations of from 0.2 to 70 ppb, showing that primary marine CaCO_3 contains little REE and that Nd/Ca is not greatly enhanced relative to seawater during carbonate precipitation. Very young marine limestone and dolomite containing no continental detritus have ~200 ppb Nd. All the carbonates are LREE enriched (-0.16≤ƒ^(Sm/Nd) ≤-0.45). Modern and very young Atlantic and Pacific carbonates have ϵ_(Nd) in the range of shallow Atlantic and Pacific seawater respectively, implying that they derive their REE from local seawater. The Nd in well preserved carbonate fossils is ≤4 × 10^4 ppb, much greater than in their modern counterparts but like the high values found for carbonates in other studies. We believe the high REE contents (at the 500 ppb level) in some detritusfree carbonates are due to REE-rich Fe-hydroxide in/on the carbonate. In favorable cases, such material may record seawater ϵ_(Nd) values, however introduction of extraneous REE may obscure the original isotopic composition of pure CaCO_3 because of its very low intrinsic primary REE abundance. Modern biogenic apatite is also shown to have very low REE content (<150 ppb Nd) but appears to quickly scavenge REE from seawater. Inorganically precipitated apatite from phosphorites has high concentrations of seawater-derived REE. Young phosphorite apatite from the Atlantic and Pacific oceans has ϵ_(Nd) in the range of the seawater from these oceans. Older apatite samples of similar age from different localities bordering common oceans record similar values of ϵ_(Nd)(T). Sedimentary apatite has ϵ_(Sr)(T) values in good agreement with the curves for ^(87)Sr/^(86)Sr of seawater as a function of time. Individual conodonts from a single formation yield the same ϵ_(Sr)(T) and ϵ_(Nd)(T). Other workers have shown that sedimentary apatite preserves seawater REE patterns. These characteristics suggest that sedimentary apatite can be used to determine ϵ_(Nd)(T) in ancient seawater. The seawater values so inferred range between −1.7 and −8.9 over the last 700 my and lie in the range of modern seawater, showing no evidence for drastic changes. High values of seawater ϵ_(Nd)(T) in the Triassic and latest Precambrian may correlate with the breakup of large continental landmasses. The initial ϵ_(Nd)(T) =−15.0 of a 2 AE old phosphorite implies the presence of ~ 1.5 AE old continental crust at 2 AE ago. The approach outlined here can be used to constrain the age of the exposed crust as a function of time.

Osmoregulation in Nestling Glaucous-Winged Gulls

-Blood samples from 32 nestling Glaucous-winged Gulls (Larus glaucescens) ranging in age from 1 to 41 days were collected at a nesting site near Vancouver, B.C. The hematocrit was positively correlated, the plasma sodium and chloride concentrations negatively correlated, and the plasma potassium and osmotic concentrations uncorrelated with age. Salt gland secretion was elicited in 23 young gulls by intravenous injection of I M NaC1. The concentration and the volume of secretion increased with age. Sodium secretion was positively correlated with the size of the salt gland. The secretion of potassium and minimum maintained concentrations of sodium were positively correlated with age. In the first hour of secretion, hatchlings eliminated 39% of the injected fluid containing 24% of the injected sodium; in contrast, the oldest nestlings removed 77% of the fluid and 55% of the sodium. Cloacal fluid voided by older salt-loaded birds was less concentrated than that of younger ones. Organ weights were determined in 20 nestlings. Kidney weight was 2-3% of the body weight regardless of age, but the relative weights of the Harderian, salt, and adrenal glands decreased with age. From the time they begin to feed, young marine birds consume foods that are hyperosmotic to their body fluids and must, therefore, eliminate excess solutes (mainly sodium and chloride) in order to remain in osmotic balance. Adult birds of marine species eliminate excess sodium chloride by means of the salt glands (Peaker and Linzell 1975), the secretion of which has roughly twice the concentration of sea water. Thus, they can drink sea water or eat salt-rich foods and still maintain osmotic balance. Adult birds also have other osmoregulatory options: e.g., they can select food items and so, theoretically at least, regulate their salt intake; those living along the coast also have access to fresh water. In contrast, nestlings do not have these choices although their parents could select food of low osmotic concentration or extract salts from it before feeding it to them. However, my observations of the food (often whole small fish or mussels) regurgitated by nestlings suggest that the adults do neither of these things. Nestlings do not ordinarily have access to water, although they have been reported to eat grass, which may provide them with free water (Ensor and Phillips 1972). They may also use dew or the parents may bring them fresh water, although neither of these possibilities seems to have been substantiated. Hence, nestling marine birds probably rely heavily on extrarenal secretion to excrete excess salt. Little has been reported about the rate of maturation of the secretory process or the factors that affect it in such nestlings. Douglas (1968) examined the size and secretory capacity of salt glands from Ad6lie Penguin chicks (Py oscelis adeliae). He found that the gland's weight and secretory rate were linearly correlat d with body size, but that the chloride concentration of the secretion was constant hroughout the growth period. He noted secretion in pipping chicks and suggested that ev n at this age, they were capable of handling the excess salt in their diet of marine inverteb es. Hughes (1968) also found that the salt gland of Common Tern chicks (Sterna hirundo) enlarged in linear fashion with body size, even though older birds were less efficient at excreting imposed salt loads than younger ones. This was due to a decrease in the volume secreted by the salt gland, not in the concentration of the secretion. However, some of the birds in that study were salt-loaded more than once during their growth period and this may have influenced their responses. Ensor and Phillips (1972) compared the secretory capacities of salt glands from 4to 5and 15to 16week-old chicks in two mixed populations of gulls (Larus argentatus and L. fuscus) that had been raised either on a marine island or an inland freshwater site. The younger birds from the marine environment were smaller than their freshwater counterparts and had larger salt glands, nearly twice as large on a weight-specific basis. The secretion of their glands was twice as concentrated in sodium and was produced at three times the rate of that from freshwater birds. These differences disappeared by the time the birds were 15-16 weeks old. In the present study, I examined the blood of birds at representative stages of the entire maturation period for age-related changes in hematocrit, electrolyte concentration, and os-

Geologic Setting and Oil and Gas Potential of Eastern United States Continental Margin North of Cape Hatteras: ABSTRACT

Two sedimentary basins, the Georges Bank basin off New England and the Baltimore Canyon Trough off the Middle Atlantic states, have been examined for geologic setting and hydrocarbon potential. Georges Bank basin, a complex-shaped trough, is on a block-faulted basement of igneous, metamorphic, and sedimentary rocks. The deepest part of the basin (deeper than 8 km) and the oldest sediments are restricted to south-central Georges Bank. Toward the northeast and southwest, the sedimentary section thins to less than 2 km over the Yarmouth Arch-LeHave platform and the Long Island platform. The only deep wells in the area are the COST G-1 and G-2; data from these wells will not be released until 60 days after the first oil and gas lease sale. Seismic correlation with the Shell M hawk B-93 well on the Scotian Shelf indicates that most of the sedimentary rocks in the Georges Bank basin are Jurassic and older. Jurassic sandstone and limestone units serve as potential reservoir rocks. Potential hydrocarbon traps may occur on structural highs associated with draping of Jurassic and basal Lower Cretaceous strata over basement blocks. The Baltimore Canyon Trough is an elongated northeast-trending basin that contains at least 14 km of Jurassic and younger marine and nonmarine sedimentary rocks. Lithologic and stratigraphic data from the COST B-2 and B-3 wells indicate that Lower Cretaceous and Jurassic rocks are predominantly nonmarine to shallow-marine sandstone and shale. Analyses of organic carbon and identification of low thermal maturity suggest that gas rather than oil will be produced. Nineteen wildcat wells have been completed; three are significant natural-gas discoveries. The largest discovery is probably associated with a large rollover trap on the downthrown block of a Cretaceous and Jurassic growth fault. Potential hydrocarbon traps in carbonate rocks beneath the present continental slope have not yet b en explored. End_of_Article - Last_Page 746------------

Sea-Level Lowering During the Illinoian Glaciation: Evidence from a Bahama "Blue Hole"

Stalagmites have been recovered from 45 meters below sea level in an underwater karstic cave ("blue hole") near Andros Island in the Bahamas. Uranium series ages, corrected for contamination of the sample by young marine carbonate replacements, show that the speleothem was deposited between 160,000 and 139,000 years before the present. This period corresponds to the Illinoian glacial event and demonstrates that sea level must have been lowered by at least 42 meters (allowing for subsidence) from its present position during this time.

Generation of unsaturated and aromatic hydrocarbons by thermal alteration of young kerogen

Abstract Monounsaturated, monoaromatic and polyaromatic hydrocarbons generated by artificial thermal alteration of young marine (Tanner basin, offshore California) kerogen were studied by computerized GC-MS. Their relative amounts changed with temperature (150–410°C) and time (5–120 hr) of heating as follows: Monounsaturates → Monoaromatics → Polyaromatics. Distribution of alkyl homologs of phenanthrene also changed with increasing degree of thermal alteration. These results are in agreement with those observed for crude oils and shales.

Thermal alteration experiments on organic matter from recent marine sediments in relation to petroleum genesis

Three fractions of organic matter: lipid (benzene:methanol-extractable), humic acid (alkali-extractable) and kerogen (residue) were extracted from a young marine sediment (Tanner Basin, offshore southern California) and heated for different times (5-116 hr) and temperatures (150-410 C). The volatile (gases) and liquid products, as well as residual material, were then analyzed. On a weight basis, the lipid fraction produced 58% of the total identified n-alkanes, the kerogen fraction 41%, and the humic acid less than 1%. The volatiles produced by heating the lipid and humic acid fractions were largely CO2 and water, whereas those produced from heated kerogen also included methane, hydrogen gas and small amounts of C2-C4 hydrocarbons. A mechanism for hydrocarbon production due to the thermal alteration of organic constituents of marine sediment is discussed.