The Uranium-Trend Dating Method: Principles and Application for Southern California Marine Terrace Deposits

Uranium-trend dating is an open-system method for age estimation of Quaternary sediments, using disequilibrium in the 238U–234U–230Th decay series. The technique has been applied to alluvium, colluvium, loess, till, and marine sediments, in this study we tested the U-trend dating method on calcareous marine terrace deposits from the Palos Verdes Hills and San Nicolas Island, California. Independent age estimates indicate that terraces in these areas range from –80 ka to greater than 1.0 Ma. Two low terraces on San Nicolas Island yielded U-trend plots that have a clustered array of points and the ages of these deposits are indeterminate or highly suspect. Middle Pleistocene terraces and one early Pleistocene terrace on San Nicolas Island and all terraces on the Palos Verdes Hills gave reasonably linear U-trend plots and estimated ages that are stratigraphically consistent and in agreement with independent age estimates. We conclude that many marine terrace deposits are suitable for U-trend dating, but U-trend plots must be carefully evaluated and U-trend ages should be consistent with independent geologic control

Deficiency of the Mitochondrial Electron Transport Chain in Muscle Does Not Cause Insulin Resistance

It has been proposed that muscle insulin resistance in type 2 diabetes is due to a selective decrease in the components of the mitochondrial electron transport chain and results from accumulation of toxic products of incomplete fat oxidation. The purpose of the present study was to test this hypothesis.Rats were made severely iron deficient, by means of an iron-deficient diet. Iron deficiency results in decreases of the iron containing mitochondrial respiratory chain proteins without affecting the enzymes of the fatty acid oxidation pathway. Insulin resistance was induced by feeding iron-deficient and control rats a high fat diet. Skeletal muscle insulin resistance was evaluated by measuring glucose transport activity in soleus muscle strips. Mitochondrial proteins were measured by Western blot. Iron deficiency resulted in a decrease in expression of iron containing proteins of the mitochondrial respiratory chain in muscle. Citrate synthase, a non-iron containing citrate cycle enzyme, and long chain acyl-CoA dehydrogenase (LCAD), used as a marker for the fatty acid oxidation pathway, were unaffected by the iron deficiency. Oleate oxidation by muscle homogenates was increased by high fat feeding and decreased by iron deficiency despite high fat feeding. The high fat diet caused severe insulin resistance of muscle glucose transport. Iron deficiency completely protected against the high fat diet-induced muscle insulin resistance.The results of the study argue against the hypothesis that a deficiency of the electron transport chain (ETC), and imbalance between the ETC and β-oxidation pathways, causes muscle insulin resistance

United States Geological Survey Reports

From abstract: "The determination of Th^232, Rn^222, and Pb^210 by isolation and subsequent activity analysis of some of their short-lived daughter products is described.

Genesis of Marine Terrace Soils, Barbados, West Indies: Evidence from Mineralogy and Geochemistry

Well-developed, clay-rich soils dominated by interstratified kaolinite-smectite are found on the uplifted coral reef terraces on the island of Barbados. The reef limestone is unlikely to have been the soil parent material however, because it is 98 per cent CaCO, and geomorphic evidence argues against the 20 m of reef solution required to produce the soils by this process. The mineralogy of the sand, silt, and clay fractions of the soils, and trace element geochemistry, suggest that aeolian materials carried on the trade winds from Africa, volcanic ash from the island of St. Vincent, and quartz from Tertiary bedrock on the island itself are the parent materials for the soils