Structural inversion and origin of a Late Ordovician (Trenton) carbonate buildup: evidence from the Tanglewood and Devils Hollow members, Lexington Limestone, central Kentucky (USA)

Throughout east–central United States, Lexington/Trenton limestones are largely Late Ordovician (Chatfieldian; mid-Caradoc), argillaceous, skeletal calcarenites, which are transgressive upward into Late Ordovician (late Chatfieldian–Edenian; mid-late Caradoc) shales and interbedded micrograined limestones. In central Kentucky, however, the same sequence is partially truncated by an unconformity and passes upward into a thicker, younger (Edenian; late Caradoc), regressive shoal complex of coarse calcarenites and calcirudites that is not generally typical of the Lexington/Trenton sequence elsewhere. The shoal complex is interpreted to have been a carbonate buildup and is partially bound by extant faults with basement precursors. Comparison of isopachous maps for pre- and postunconformity buildup units with basement structural lineaments suggests that the buildup is related to reactivation—and in one prominent case, inversion—of the basement structures. The coincidence of structural reactivation, inversion, and buildup development with other major regional, cratonic changes may reflect a reorganization of cratonic, far-field forces accompanying a nearly coeval reversal in the polarity of Taconic subduction.     

Relationship between Cultural Factors and Nematodes on Merion Kentucky Bluegrass

A 2-year study was conducted on Merion Kentucky bluegrass turf (Poa pratensis) to identify potential relationships among seasonal population dynamics of nematodes, chemical applications, thatch, tillering, dollar spot caused by Sclerotinia homoeocarpa, clipping weight, and other factors. Numbers of Tylenchorhynchus maximus determined during June were inversely related to the wet weight of grass from May. One or more monthly counts of Paratylenchus hamatus, Criconemella rusium, and T. maximus negatively correlated with the numbers of spring tillers. Applications of benomyl, used for dollar spot control, decreased numbers of T. maximus and free-living nematodes, and this chemical was associated with acidification of the thatch. Hoplolaimus galeatus levels were associated with an estimated 8% increase in the severity of dollar spot.     

Effects of Nematicides on Nematode Densities in Turf in Connecticut

The plant-parasitic nematodes Criconemoides lobatum, Hoplolaimus tylenchiformis, and Tylenchorhynchus dubius were present in the top 7.5 cm of sod consisting of numerous stolons and fibrous roots. Phenamiphos and 1,2-dibromo-3-chloropropane (DBCP) controlled all three species, whereas ethoprop and oxamyl controlled H. tylenchiformis and T. dubius but not C. lobatum. Benomyl and carbofuran controlled H. tylenchiformis but had poor control of C. lobatum and T. dubius. The effectiveness of carbofuran varied with the type of formulation, being most effective as a quick-release formulation. C. lobatum was the most difficult to control with chemicals. No chemical treatment improved the growth of ''Astoria colonial'' bentgrass (A. tenuis Sibth.) or Kentucky bluegrass (Poa pratensis L.) under the moist condtions prevalent in these tests.