The results of drilling on Resolution and Allison guyots, in the Mid-Pacific Mountains (MPM), document a long history of volcanism, subsidence, and accumulation of Hauterivian-Albian shallow-water carbonate sediments. Mid-Cretaceous emersion was followed by subsidence and accumulation of pelagic sediments.Basement beneath Resolution Guyot is subaerial flows of alkalic basalt, with radiometric dates averaging 127.6 ±2.1 Ma, emplaced at about 14°S. Overlying shallow-water carbonates are 1620 m thick. Sediments at Site 866, 2 km inward from the platform edge, were deposited in shallow subtidal to intertidal depths, with intermittent subaerial exposure. At Site 867, 0.5 km from the platform edge, beach and storm deposits are common, and at Site 868,0.1 km from the edge, sponges and rudists in life positions indicate a platform-margin environment.At Allison Guyot, alkalic basalt sills were cored at the bottom of Hole 865A. Seismic profiles suggest as much as 600 m of sediments underlie the sills, which have 40 Ar/ 39 Ar radiometric dates averaging 110.7 ±1.2 Ma. The drilled strata, 730 m thick, extend from near the base to nearly the top of the Albian. The section begins with about 200 m of clayey limestone deposited in quiet, swampy waters. Upward, clays gradually disappear, reflecting the burial of volcanic hills as the seamount subsided. The rest of the series is wackestone deposited in subtidal to intertidal environments.Core and logging data at both guyots show shallowing-upward cycles of 3 to 10 m thick. Fourier analysis yields estimates of about 100 ka as the most common frequency. Longer-term fluctuations in sea level are suggested by facies successions at a decameter scale. Diagenesis was dominated by dissolution of aragonite, and cements are now marine, low-magnesium calcite. Pore-water data show the entire succession to be open to modern seawater. Dolomite dominates in the lower 400 m of carbonate strata at Resolution Guyot, and Sr-isotope data suggest much of it formed 15 to 20 m.y. after deposition. Compaction of limestone over buried basement topography proceeded apace with deposition and continued after drowning of the guyots.During the latest Albian, a fall in relative sea level of nearly 200 m exposed limestone strata on both guyots to subaerial and wave erosion, but whether the cause was tectonic or eustatic is not yet known. By mid-Turonian time, the guyots had re-submerged, but only pelagic sediments accumulated. Why no further shallow-water sediments accumulated on the guyots is a mystery. They were at about 8°S (Resolution) to 11°S (Allison) at the time of emergence. Upper Cretaceous pelagic sediments are preserved only in cavities within Albian limestone. Eocene and Paleocene sediments on Allison Guyot, about 120 m thick, were deposited at near-equatorial latitudes. The Lower Cretaceous platform is variably encrusted with phosphorite and ferromanganese oxides, even where buried beneath pelagic sediments.Primary control on acoustic-wave velocity is from diagenetic changes in density. Cha...
Introduction Although Obstructive Sleep Apnea (OSA) is prevalent in the military population, traditional scoring/clinical cut-offs of available screening tools may not be appropriate for this younger, slimmer population. We additionally have limited information regarding utility of OSA screening in those with history of mild traumatic brain injury (mTBI). The current study compared multiple STOPBANG scoring methods to determine how well they were associated with self-reported sleep measures in an mTBI sample. Methods Secondary analyses were conducted from a large database of evaluations from a multi-center, longitudinal study of mTBI. Participants were included if they had completed the STOPBANG and additional sleep measures. The subsequent sample (N=486) included participants with history of mTBI (n=408) and controls (n=78). The sample was predominantly male (n=421) with a mean age of 39 (IQR = 31/37/47). Results Sleep efficiency was not significantly associated with any STOPBANG scoring, in the total sample or when controlling for mTBI. In the total sample, sleep quality was most strongly associated with traditional STOPBANG scoring (STOPBANG ≥ 3, β=0.51). Sleep duration was most strongly associated with Snoring/Tired/Hypertension (STP = 3, β=0.79). When controlling for mTBI, duration was most strongly associated with traditional scoring (β=0.48), while sleep quality was most strongly associated with Snoring/Tired/Hypertension (β=0.78). Follow-up analyses demonstrate a significant difference in correlation between groups for STP/Sleep Quality, with a stronger correlation for those without mTBI. Conclusion The STOPBANG measure was significantly associated with self-reported sleep quality/duration measures, but not sleep efficiency. Although traditional clinical cut-offs for OSA predicted sleep measures in this sample, the relationship between risk scores and outcomes became more nuanced when history of mTBI was included. Future studies are needed to understand the relationship between OSA risk and subsequent diagnosis in the mTBI population. Support Defense and Veterans Brain Injury Center (GDHS,W91YTZ-13-C-0015), DOD(W81XWH-12-2-0095), VA(I01 CX001135)
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