Heat flow constraints on the South Pacific Superswell

The South Pacific superswell has been defined as a large region of anomalously shallow bathymetry, low Love wave velocities, and low effective elastic thicknesses relative to those predicted for its age. These phenomena have been interpreted as reflecting a combination of lithospheric reheating and thinning, and dynamic uplift due to mantle flow. We use heat flow data to better constrain the thermal structure of this region and examine the predictions of various possible models. The average heat flow for the superswell region does not differ significantly from that for lithosphere of similar ages elsewhere on the Pacific plate. Given their uncertainties, the heat flow data imply that thermal lithospheric thickness exceeds 60 km, but cannot discriminate between greater thicknesses. The lack of observed high heat flow appears not to be explained by biases due to water circulation in the thin sediment cover, since the superswell heat flow is not higher than for sites elsewhere with similar sedimentary environments. The Darwin Rise has been proposed as a fossil superswell in the Cretaceous, on the basis of the many similar characteristics to the South Pacific superswell. We find that the Darwin Rise heat flow values do not exceed those for similar ages elsewhere in the Pacific and Atlantic. This observation suggests that any thermal effects associated with the formation of the Darwin Rise are no longer present, and it is consistent with the idea of a fossil superswell. The surface heat flow data thus provide no evidence that the temperatures in the uppermost portion of the lithosphere; are significantly higher in the entire superswell region than in other areas of comparable age. This observation is intriguing given the suggestion that the thin effective elastic thicknesses inferred from seamount loading may reflect reheating of the lithosphere. Models in which the plate thicknesses and/or the basal temperatures are increased to yield temperatures high enough to explain the low effective elastic thicknesses predict surface heat flow much higher than observed. Reheating the lithosphere, as is proposed for hot spots, yields temperatures adequate to explain the effective elastic thicknesses only if reheating occurs at very shallow depths, and again implies a surface heat flow much greater than observed. Hence, unless shallow reheating is somehow localized beneath the seamounts, the thinner elastic thicknesses may reflect mechanical, rather than thermal, weakening of the lithosphere

The transition between the Sheba Ridge and Owen Basin: rifting of old oceanic lithosphere

Magnetic quiet zones are present along the margins of the entire length of the Gulf of Aden to the Owen fracture zone. This includes the easternmost 300 km between the eastern edges of Arabia and Africa to the Owen fracture zone where old oceanic lithosphere was rifted to form the Sheba Ridge. Within this easternmost region the boundary between the quiet zone and the old oceanic lithosphere is marked by ridge complexes, the Sharbithat Ridge Complex to the north and the Error Ridge Complex to the south. These ridge complexes, which lack a magnetic signature, occupy a structural position similar to the hinge zones at the continental margins to the west. They appear to have formed early in the opening of the Gulf of Aden or perhaps to have been pre-existing features. The boundary between Sheba Ridge and the northern magnetic quiet zone is often marked by an abrupt end of the Sheba Ridge seafloor spreading magnetic anomaly pattern and a sharp basement deepening to the north. The boundary between the East Sheba Ridge and northern magnetic quiet zone becomes less distinct near the Owen fracture zone. This is also accompanied by changes in the East Sheba Ridge, specifically a decrease in magnetic anomaly amplitudes, increase in ridge flank depths and a loss of the ‘cooling-curve’ ridge flank shape. This may be the result of lower mantle temperatures in the vicinity of the Owen fracture zone. The sediments within the magnetic quiet zone can be divided into a lower disturbed unit and an upper unit consisting of flat-lying reflectors. The disturbance of the lower sediments may have resulted from a period of diffuse extension in the magnetic quiet zone prior to the establishment of the Sheba Ridge spreading center. The similarity of the easternmost quiet zone to quiet zones at rifted continental margins leads to the suggestion that these regions were formed by diffuse extension of old oceanic lithosphere. Using a two-layer lithospheric attenuation model and assuming extension during a period of 15Myr followed by 10Myr of cooling, the basement depths and heat flow measurements can be adequately matched. The modeling implies 45 per cent crustal extension in the quiet zone. The amount of extension calculated is compatible with documented motion between Arabia and Africa. The old oceanic lithosphere thus must have been substantially thinned to a thickness similar to 10-14Myr old ocean before seafloor spreading was initiated at the Sheba Ridge

Has the Wharton Basin's Heat flow been perturbed by the formation of a diffuse plate boundary in the Indian Ocean?

The Central Indian Ocean region has heat flow higher than expected for its lithospheric age. This heat flow anomaly is thought to be associated with deformation of sediment and crust and high seismicity. To better constrain the nature of this deformation, we examine the spatial variation of the heat flow. Previous work suggested high heat flux also in the Wharton Basin to the east, which shows less seismicity and deformation. Using new values for lithospheric age from reinterpretation of the magnetic anomalies, we have reexamined the heat flow and found it no higher than expected, in contrast to the Central Indian Basin. This spatial distribution of heat flow highs and expected values is consistent with the pattern of seismicity and deformation and the predictions of the recent diffuse plate boundary model [Wiens et al., 1985] for the region

Topographic relief and sediment thickness: Their effects on the thermal evolution of the oceanic crust

We compiled a suite of 490 heat flow measurements from the Pacific Ocean in areas with less than 85 m of sediment. Heat flow patterns at different basement ages vary with topographic relief. Areas with reliefs 300 meters are conductively blanketed at 70–90 m.y. and convect out to ≥ 90–110 m.y

Design of the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS)

The Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) is a multi‐component epidemiological and neurobiological study designed to generate actionable evidence‐based recommendations to reduce US Army suicides and increase basic knowledge about the determinants of suicidality. This report presents an overview of the designs of the six components of the Army STARRS. These include: an integrated analysis of the Historical Administrative Data Study (HADS) designed to provide data on significant administrative predictors of suicides among the more than 1.6 million soldiers on active duty in 2004–2009; retrospective case‐control studies of suicide attempts and fatalities; separate large‐scale cross‐sectional studies of new soldiers (i.e. those just beginning Basic Combat Training [BCT], who completed self‐administered questionnaires [SAQs] and neurocognitive tests and provided blood samples) and soldiers exclusive of those in BCT (who completed SAQs); a pre‐post deployment study of soldiers in three Brigade Combat Teams about to deploy to Afghanistan (who completed SAQs and provided blood samples) followed multiple times after returning from deployment; and a platform for following up Army STARRS participants who have returned to civilian life. Department of Defense/Army administrative data records are linked with SAQ data to examine prospective associations between self‐reports and subsequent suicidality. The presentation closes with a discussion of the methodological advantages of cross‐component coordination. Copyright © 2013 John Wiley & Sons, Ltd .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102177/1/mpr1401.pd

Neurocognitive Function and Suicide in U.S. Army Soldiers

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138894/1/sltb12307_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138894/2/sltb12307.pd

Screening Young Adults for Prevalent Chlamydial Infection in Community Settings

Community-based testing may identify young adults in the general population with sexually transmitted chlamydial infection. To develop selective screening guidelines appropriate for community settings, the authors conducted a cross-sectional analysis of the National Longitudinal Study of Adolescent Health Wave III (April 2, 2001 – May 9, 2002)

Field procedures in the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS)

The Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS) is a multi‐component epidemiological and neurobiological study of unprecedented size and complexity designed to generate actionable evidence‐based recommendations to reduce US Army suicides and increase basic knowledge about determinants of suicidality by carrying out coordinated component studies. A number of major logistical challenges were faced in implementing these studies. The current report presents an overview of the approaches taken to meet these challenges, with a special focus on the field procedures used to implement the component studies. As detailed in the paper, these challenges were addressed at the onset of the initiative by establishing an Executive Committee, a Data Coordination Center (the Survey Research Center [SRC] at the University of Michigan), and study‐specific design and analysis teams that worked with staff on instrumentation and field procedures. SRC staff, in turn, worked with the Office of the Deputy Under Secretary of the Army (ODUSA) and local Army Points of Contact (POCs) to address logistical issues and facilitate data collection. These structures, coupled with careful fieldworker training, supervision, and piloting, contributed to the major Army STARRS data collection efforts having higher response rates than previous large‐scale studies of comparable military samples. Copyright © 2013 John Wiley & Sons, Ltd .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102238/1/mpr1400.pd