DIGITAL uses SCSI technology in most of its storage products and consequently has led major standards and industry bodies to improve the technology in the following areas: increased synchronous data phase speed beyond fast SCSI; longer, more complex electrical configurations by means of expander circuits; versatile and more manageable connectivity through a smaller, improved physical interconnect; and dynamic device insertion and removal. Data phase transmission rate extension is achieved through understanding and controlling silicon chip timing and transmission media parameters. Using expander devices to confine transmission line effects to shorter segments allows large increases in the maximum distance between devices and in the device population within the same SCSI domain. Expanders enable complex, hublike configurations to be created without changing existing SCSI devices or software. The use of 0.8-millimeter connector technology and consideration of cable losses has reduced the physical size of the external shielded interconnect by approximately two thirds, decreased the number of parts required to support complex configurations by a factor of 10, and increased the interconnect density to the same level used in serial SCSI. Finally, the mating and demating events that occur during device insertion and removal produce a spectrum of small, undetectable, electrical disturbances on the active bus that appear to be limited by the physics of the media and device capacitance.

For three years the Carbonate Rock Subcommittee of the A.A.P.G. Research Committee has been compiling data for approximately 500 terms that are used in describing and naming limestone and dolomite. With the great advance in knowledge about these rocks, resulting mainly from studies associated with the occurrence of petroleum in reefs and limestone banks, the body of nomenclature is expanding constantly. Contributing to the proliferation, but not without "mixed blessings," are investigations of ancient rocks, modern sediments, environments of deposition, dolomitization, mineral species, grain-sizes, fabrics, and diagenetic processes. The subcommittee will assemble these terms, dissect them, illustrate their important concepts, and publish the results. By means of the illustrations to accompany the final report, the subcommittee hopes to consolidate the best contemporary ideas and at the same time prevent further confusion and synonymy in this highly complex family of petroliferous rocks. End_of_Article - Last_Page 616------------

Four major evaporite cycles are widely present in Lower and Middle Permian strata of western Oklahoma, interstratified with clastic sediments in a sequence 4,000 feet thick. Named in ascending order the Wellington, Cimarron, Blaine (including salt beds that underlie and overlie it in subsurface), and Cloud Chief, they consist almost exclusively of anhydrite and rock salt. Thin beds of dolomite also are present, but potassium salts have not been found. The cycles diminish in thickness upward, as the maximum thickness of the lower two is 1,000 feet, the next younger 600 feet, and the youngest 100 feet. The uppermost or Cloud Chief evaporites consist only of massive anhydrite, whereas each of the three lower cycles is divisible into individual subcycles, some of them traceable over a region covering more than 15,000 square miles. A single cycle of anhydrite overlain by salt characterizes each of these major units. Dolomite-anhydrite couplets in the 150-foot thickness of the Blaine also are outstanding for their demonstrable continuity and persistence. Continuous cores of nearly pure rock salt 150 feet thick in the lower part of the Cimarron evaporites likewise show pronounced cyclical development, which is reflected in the isomorphous potassium of the halite, in the range of 100 to 400 ppm. Low potassium values in the lower part of each cycle contrast with high values in the upper part, producing geochemical discontinuities at the boundaries between successive cyles. Also arranged in cycles are the clastic sediments of the framework that contains the cyclic evaporites. Particularly conspicuous are the interbedded brownish red and gray-green shales of the Flowerpot, Blaine, and Dog Creek Formations. Investigations of boron thus far suggest a marine environment for the shales, and in one area the highest shale values (250 ppm boron) are associated with as much as 4.5 per cent copper. Cyclicity in the Permian evaporites of Oklahoma are related to cyclical changes in environment during the progressive sinking of a sedimentary basin. Roles are doubtless played by tectonism and climate, in forming the basin itself as well as in producing the aridity necessary for the precipitation of evaporites, but eustatic change in level of the sea must also have been a prominent factor during Early Permian time, when continental glaciation in the southern hemisphere was repeatedly raising and lowering the sea. End_of_Article - Last_Page 359------------

The Arbuckle Mountain region of south-central Oklahoma is made up of thick Paleozoic rocks that were folded and faulted during several orogenic episodes within Middle and Late Pennsylvanian time. Pre-Pennsylvanian rocks ranging in age from Cambrian through Mississippian are differentiated into a southwestern basin province containing nearly 12,000 feet of sediments and a northeastern shelf province containing 7,000 feet of sediments. Ordovician rocks, principally carbonates, make up more than two-thirds of the stratigraphic section, having a thickness of 8,500 feet in the basin and 5,000 feet on the shelf. The region persisted in pre-Pennsylvanian time as a continually sinking site of marine deposition, in which slight local uplift but no mountain-building orogeny is indi ated. During Pennsylvanian time 17,000 feet of strata that are chiefly fine-grained clastic sediments were deposited in the Ardmore basin, adjoining the Arbuckle Mountains on the south, nearly in the same position as, and doubtless the continuation of, the older Ordovician basin. In the central part of the Arbuckle Mountains and along the northern edge, Pennsylvanian marine clastics and limestone are interstratified with conglomerates in a sequence not more than 5,000 feet thick. These rocks were deposited over the site of the earlier shelf area. Structural differentiation of the Arbuckle Mountains began in early mid-Pennsylvanian time with the slow epeirogenic rise of the shelf area--the Hunton anticline--which resulted in the spreading of conglomeratic strata in surrounding areas of marine deposition. The Hunton anticline evidently remained emergent and was being continually uplifted through most of the Middle and Late Pennsylvanian. Total uplift was approximately 4,100 feet, nearly all of which was attained by gentle domal warping, and the Hunton anticline now stands as the most simple of all the major Arbuckle Mountain structural features. It is the only anticlinal structure to be uplifted so little that Lower Ordovician, Cambrian, and pre-Cambrian rocks are not exposed. While the shelf area was rising, the basin area continued to sink and to receive sediments, partly derived from the eroding Hunton anticline. Local uplift on the northeast flank of the present Arbuckle anticline and north flank of the Tishomingo anticline resulted in pre-Desse erosion of all or parts of the Atoka, Wapanucka, and Springer formations, but the south flanks of these anticlines are structurally and stratigraphically conformable with the thick Pennsylvanian rocks of the Ardmore basin. Neither the Arbuckle anticline nor the Tishomingo anticline was a significant positive area until after the close of Hoxbar time. Principal deformation of the Arbuckle Mountains was during the Late Pennsylvanian Virgil epoch. The Hunton anticline underwent its last and one of its strongest orogenic pulses just before Ada (mid-Virgilian) time, and it is inferred that the chief folding of the Arbuckle anticline, as well as the Tishomingo anticline, Mill Creek syncline, and Belton anticline, occurred during this episode. This was a short but severe time of structural deformation. The Arbuckle anticline was sharply folded, overturned on its north flank and locally on its south flank, and faulted in its axial part by thrusting. Parts of the fault systems probably were established at this time. Structural uplift was so End_Page 425------------------------------ great that the Reagan sandstone of Cambrian age was locally exposed, from which it can be deduced that 11,000 feet of pre-Pennsylvanian rocks and probably at least 5,000 feet of Pennsylvanian strata had been stripped away. The orogenic product derived from this deformation was the Collings Ranch conglomerate, a massive limestone boulder deposit which has an exposed thickness of 2,000 feet and a probable initial thickness of 3,000 feet. From the character of the rocks comprising the conglomerate, it is certain that the source areas were the Arbuckle and Tishomingo anticlines. A slightly later surge of orogeny continued and even intensified the deformation. Block faulting, accompanied by some folding, broke the folded complex along previously established structural lines into grabens and horsts elevating the anticlines to greater heights and permitting the exposure, after erosion, of large granite areas in the Tishomingo and Belton anticlines. The Collings Ranch conglomerate was mostly eroded except where preserved in grabens, and the new orogenic deposit, the Vanoss conglomerate of latest Pennsylvanian age, was spread as a feldspar-rich blanket on the strongly folded and eroded edges of the older rocks. This younger conglomerate has a maximum thickness of 650 feet on the western edge of the Mill Creek syncline, nearest the Arbuckle and Tishomingo anticline . At a few places the lower part of the Vanoss conglomerate is faulted and slightly folded by a final weak pulse, but the overlying younger rocks, including the Hart limestone which is considered to be the base of the Permian system, are virtually flat and mark the close of the Arbuckle orogeny in this region. One of the major problems in Arbuckle Mountain structural interpretation concerns the nature of the northwest-trending through-going faults, principally the Washita Valley fault, Reagan fault, and the Sulphur fault zone. These have been variously interpreted as normal, thrust, scissor, and rift faults. Dips observed or inferred on the outcrop, together with information from drill holes, indicate that these faults locally have normal and locally thrust relations, and the conclusion is reached that both the Washita Valley and Reagan faults have a component of strike-slip movement. The Tishomingo anticline is believed to have moved northwestward between these two faults, probably as a result of stress transmitted from the Ouachita Mountains. End_of_Article - Last_Page 426------------

The Arbuckle limestone of upper Cambrian and lower Ordovician age is 6,700 feet thick and is divided into eight formations which in ascending order are Fort Sill, Royer, Signal Mountain, Butterly (top of Cambrian), McKenzie Hill, Cool Creek, Kindblade, and West Spring Creek. These units crop out over 100 square miles of the Arbuckle anticline in the western Arbuckle Mountains. Principal features of Arbuckle limestone stratigraphy are: 1. The sequence is about 98 per cent carbonate rock, the remaining part being: (a) thin sandstone beds, and (b) shale, chiefly in the form of partings. 2. Limestone is the original deposit and dolomite in general is a replacement of it. The limestone types consist mostly of: (a) algal beds, (b) calcarentite or pellet limestone, grading into intraformational conglomerate, (c) fine-grained limestone, either laminated or massive, and (d) oolitic limestone. 3. Distribution of sand and chert is of value for subdivision and correlation. Sand is lacking in Cambrian strata except coarse arkose at or near the Cambrian-Ordovician boundary, whereas Simpson type sand in limestone is common in Ordovician formations. Chert is rare in Cambrian but prevalent in Ordovician strata. 4. No physical evidence for unconformity is recognized in the Arbuckle limestone. 5. Faunal zones are persistent laterally and are close approximations to true time horizons. 6. Major dolomite-limestone facies are chiefly in Cambrian beds and are regional in scope, the contacts changing progressively along strike at the rate of 5-17 feet per mile. The dolomite-limestone ratio increases eastward. Principal features of structural history are: 1. Anticlinal folding, overturning of the north limb and locally of the south, and accompanying thrust faulting, in post-Hoxbar, upper Pennsylvanian time, coinciding with major folding of the Ardmore basin. 2. Deposition of stratified limestone conglomerate more than 2,000 feet thick in the Turner Falls area, and folding of this conglomerate as part of the Arbuckle orogeny. 3. Later elevation and high-angle faulting, accompanied by only minor folding, in latest Pennsylvanian (Vanoss) time, resulting in deposition of the younger and thinner Pontotoc conglomerate as a bordering rim on the north and west flank of the Arbuckle Mountains. End_of_Article - Last_Page 621------------

Rocks of a unique type have been recently discovered in the Wichita Mountains of southwestern Oklahoma. Composed principally of zeolites and opal, with variable amounts of dolomite and calcite, these rocks occur as four scattered outcrops in Kiowa County. They appear to be stratified and have a maximum thickness of 47 feet. The name is given to these zeolite-opal rocks. The Tepee Creek sediments rest with an erosional unconformity on anorthosite and contain rounded pebbles of that igneous rock. The formation, furthermore, is intruded by several small granite dikes of pre-Cambrian age. The unconformity, the zeolite-opal rocks, and the period of igneous activity represented by the granite dikes have not been previously recognized. Evidence is presented to show that the zeolites and opal have formed by the alteration of a sediment which was essentially an anorthosite-graywacke, with some beds containing dolomite and perhaps limestone. The zeolites, chiefly natrolite, and the opal are secondary. The zeolites probably were derived diagenetically by the action of saline waters of a pre-Cambrian sea on the labradorite of the detrital anorthosite. The opal may be partly diagenetic but some of it is later, for it replaces natrolite.