ABSTRACT This one-day field trip of regional geologic significance goes from Spokane, Washington, north along the Pend Oreille River to the Lafarge limestone quarries in the Metaline Formation near Metaline Falls, Washington, USA. Along the way, we will discuss local geologic and geomorphic features, archaeology of the Native culture, features of Pleistocene glaciation and the Eocene Newport fault in the Pend Oreille valley, and highlights of roadcuts and rock types. The main focus of the field trip centers on the paleontology of the lower bedded member of the Metaline Formation in the Lafarge quarry. Based on recent fossil identification of recently discovered trilobites, the age of the lower bedded member has been refined to Series 2-Stage 4 of the Cambrian. We will examine potential new species at stopping points within the quarry, identify key units of stratigraphy and relate them to the stratigraphic column of the guide, and include a structural geology discussion. Deformed trilobites, cleavage, and calcite-filled fractures indicate NW-SE compression during Mesozoic Cordilleran tectonism.

Abstract The middle member of the Cambrian Metaline Formation in northeastern Washington State is a 360-m-thick dolostone unit containing seven depositional and diagenetic lithotypes. Four major dolomite crystal fabrics (A-D) have been identified within these rocks. Cathodoluminescence was required to show subtle features in the dolomite crystal fabrics and helped separate discrete stages in the development of the four fabrics. Fabric A displays bright orange luminescence and is composed of micritic dolomite. Fabric B is a hypidiotopic and xenotopic fabric that shows a red-blue luminescence that does not outline individual crystals. Fabric C is more coarsely crystalline than fabric B and displays the same luminescence as fabric B. Fabric D is composed of zoned, brightly colored luminescent crystals of white sparry and saddle dolomite. Zebra dolomite in the Metaline Formation is a special feature formed when fabric D crystals filled subparallel, linear vugs in fabrics B and C. Each crystal fabric is related to one or more diagenetic process or diagenetic environment. The crystal fabrics can be interpreted for the Metaline section specifically and for dolostones in general. Fabrics, processes, and environments include: (1) fabric A (micritic dolomite), surface-controlled, penecontemporaneous, open systems, where surface-derived fluids cause dolomitization of original cal-cite/aragonite sediments and limestones; (2) early fabric B (idiotopic fabric), intraformational open systems, where surface-derived fluids or shallow-subsurface fluids cause dolomitization; (3) final form of fabrics B and C (hypidiotopic and xenotopic fabrics), intraformational closed systems, where subsurface fluids cause dolomitization diagenesis or neomorphism of earlier formed dolomites; and (4) fabric D (white sparry and saddle dolomite), deep-subsurface, secondarily opened systems that precipitate dolomite cements. Because each environment and its associated process produces a particular dolomite crystal fabric, each major diagenetic environment determines an end-member fabric that may be formed and preserved. Relicts of prior fabrics may or may not remain in the rock, depending on the completeness with which later processes develop. Often, only cathodoluminescence can show the relicts of early processes. Complex dolostones, such as the middle member of the Metaline Formation, can thus be interpreted by analyzing their contained diagenetic-crystal fabrics. By matching fabric with process and diagenetic environment, the evolution of a dolostone can be traced.

Abstract Lower Cambrian–Lower Ordovician passive-margin sediments were deposited across northeastern Washington, northern Idaho, and western Montana. Lower Cambrian strata record the initial transgression onto Laurentia in northeastern Washington. Middle Cambrian–Lower Ordovician units were deposited across a much broader area and record the establishment of a western ooid-algal shoal complex that restricted water circulation in an intrashelf basin that formed between the shoal and craton. Long-standing topographic highs in the region include Montania, which may have controlled the location of the ooid-algal shoal complex, and the Lemhi arch, which served as a western source area for siliciclastic sediment input. The Sauk megasequence sediments were deposited in multiple grand cycles that are regionally correlative. Each grand cycle consists of a shale and sandstone base deposited as sea level transgressed onto the craton. The basal siliciclastic units are gradationally overlain by carbonate, which was deposited as sea level continued to rise and an extensive carbonate platform developed. Some of the boundaries between the grand cycles are unconformities, recording rapid changes in sea level. Meter-scale shallowing-upward cycles are common within grand cycles, but they have not yet been regionally correlated.

There are several isolated outcrops (outliers?) of Devonian rocks in the Pacific Northwest (Washington and Oregon), USA. A locality in northeastern Washington, Limestone Hill, is considered in detail, and other small outcrops in northwest Washington and central Oregon are discussed. Limestone Hill is a Paleozoic outlier. The locality has Ordovician and Silurian (Llandovery and Wenlock) strata, Lower Devonian (Lochstone conglomerate, and Upper Devonian (Frasnian) carbonates with fossils. It has long been known that the area has many allochthons, and it has been assumed that Limestone Hill represents lithologies deposited much farther west. More recent data suggest that Limestone Hill is parautochthonous. Several brachiopod taxa, previously unknown from the Frasnian portion of Limestone Hill, have been found recently and are described herein. The brachiopod faunule consists of Emanuella sp., “ Allanella ” engelmanni , Cyrtina sp., Thomasaria sp., and an athyridid. These brachiopods appear to be like coeval faunas in Idaho, Montana, Utah, and Nevada, although more species assignments must be made. Frasnian brachiopods are in serious need of updates, as Famennian miospore and acritarch data suggest significant basin restriction and reduced seaway connectivity, with at least ephemerally extensive land areas with ubiquitous land plant taxa.