Texas A&M University completed excavations at the Gault site (41BL323) in Bell County, Texas, in the spring season of 2000. Located at the head of Buttermilk Creek, past inhabitants have enjoyed perennial springs and a variety of natural resources available in the immediate area, including high quality chert from the Balcones Escarpment of the Edwards Plateau. Chipped stone material diagnostic of the Clovis period was recovered during the TAMU block excavation, informally referred to as the "Lindsey Pit," from clay deposits approximately 35 cm thick. Natural agents that may have impacted contextual integrity of the Clovis cultural deposits include stream action, pedoturbation, and bioturbation. Artifact spatial analyses examined long axis orientations and artifact degree of dip to identify non-random patterns that would result from stream action. Vertical and horizontal relationships of refitting artifacts were examined to evaluate post-depositional displacement. Orientations of chipped stone artifact long axes and inclination were found to be statistically random, with minor patterns that reflect the paleotopography. Thirty-three groups of refitting artifacts were identified, none of which contained elements recovered from deposits more recent than the Clovis clays. Five groups have elements that appear to come from both of the Clovis clay deposits, indicating a small degree of vertical displacement. The results of this research indicate the clays bearing Clovis materials retained a high degree of integrity such that the spatial patterns preserved in the archaeological record at this location are the result of cultural activities and not natural processes. Though time-consuming in the field and laboratory, additional fine-grained analyses such as artifact orientation and refit studies provide separate lines of evidence to account for natural processes that may have acted to obscure the original patterns of the archaeological record, and our understanding of past human cultures.

Polybrominated dibenzo-p-dioxins (PBDD) and dibenzofurans (PBDF) are a group of compounds of emerging interest as potential environmental stressors. Their structures as well as toxic responses are similar to the highly characterized toxicants polychlorinated dibenzo-p-dioxins. High levels of PBDDs have been found in algae, shellfish, and fish, also from remote areas in theBaltic Sea. This thesis presents studies on PBDD behavior in fish and offspring, and natural formation of PBDDs from naturally abundant phenolic precursors. The uptake, elimination, and maternal transfer of mono- to tetraBDD/Fs were investigated in an exposure study reported in Paper I. The effects of PBDDs in fish were examined in a dose-response study (Paper II). It was shown that fish can assimilate PBDD/Fs from their feed, although non-laterally substituted congeners were rapidly eliminated. Laterally substituted congeners were retained as was congeners without vicinal hydrogens to some extent. PBDD/Fs were transferred to eggs, and congeners that were rapidly eliminated in fish showed a higher transfer ratio to eggs. Exposure to the laterally substituted 2,3,7,8-TeBDD had significant effects on the health, gene expression and several reproduction end-points of zebrafish, even at the lowest dose applied. The geographical and temporal variations of PBDD in biota samples from the Baltic Seasuggest biogenic rather than anthropogenic origin. In Paper III, bromoperoxidase-mediated coupling of 2,4,6-tribromophenol yielded several PBDD congeners, some formed after rearrangement. The overall yield was low, but significantly higher at low temperature, and the product profile obtained was similar to congener profiles found in biota from the Swedish West Coast. In Paper IV, photo­chemi­cally induced cyclization of hydroxylated polybrominated diphenyl ethers under natural conditions produced PBDDs at percentage yield. Rearranged products were not detected, and some abundant congeners do not seem to be formed this way. However, the product profile obtained was similar to congener profiles found in biota from the Baltic Proper. Since the PBDD congeners found in biota have a high turn-over in fish, the exposure must be high and continuous to yield the PBDD levels measured in wild fish. Thus, PBDDs must presumably be formed by common precursors in general processes, such as via enzymatic oxidations, UV-initiated reactions or a combination of both. The presented pathways for formation of PBDDs are both likely sensitive to changes in climatic conditions.