A method is given for modifying the estimated radiocarbon dates of two samples when they are known to be in the wrong order.

Small sample 14C dating is tested using conventional as well as high-resolution low-level liquid scintillation (LS) spectrometers. Contrasted are the results obtained dating -.25, 125 and 250mg of elemental carbon in standard size counting vials (3mL) and 0.3mL teflon and quartz vials. It is demonstrated that the improved performance of the 0.3mL counting vials enables just adequate resolution of 25mg and very good resolution of 100mg carbon samples both at Modern and Old age limits when the determination is made in a highresolution low-level LS spectrometer.

Calcareous tufa from five sites in southern Poland, representing several most typical conditions of tufa sedimentation, were chosen for 14C, 13C, and 18O measurements. These tufas were deposited in a high-energy turbulent stream (the Raerawka site), in streams with moderate but variable flow (Rzerzusnia and Trzebienice), and in semilimnic conditions (Sieradowice site). Sediments of the Gliczarow site represent spring travertines. In all but the latter site, direct comparison of 14C dates of carbonate and organic fractions was possible, leading to an estimate of initial apparent age of carbonate sediments. Clear correlation was found between the value of initial apparent age of tufas and the hydrodynamic conditions of sedimentation. Corresponding values range from ca 3900 yr (Raetawka) to 910 yr for semilimnic sediments (Sieradowice). Intermediate, almost identical values, equal to 2460 +/- 200 yr and 2100 +/- 160 yr, were obtained for tufas from Rzerzusnia and Trzebienice, respectively. Detailed sedimentologic classification of tufaceous deposits is presented and some primary and secondary factors affecting the accuracy of radiocarbon dates of various types of tufas are also discussed.

A re-evaluation of the Longin collagen-extraction method shows that a lower reflux temperature reduces degradation of protein ("collagen") remnants. This allows additional purification through ultrafiltration to isolate the >30kDalton fraction of the reflux product.