John Warme

• PhD, UCLA, 1966
• Professor Emeritus at Colorado School of Mines

We interpret a discrete, anomalous ~10-m-thick interval of the shallow-marine Middle to Late Devonian Valentine Member of the Sultan Formation at Frenchman Mountain, southern Nevada, to be a seismite, and that it was generated by the Alamo Impact Event. A suite of deformation structures characterize this unique interval of peritidal carbonate facie...

Describes six processes and features connected with 382-m.y. Late Devonian middle Frasnian Alamo Impact in southern Nevada

A wide variety of impact processes and resulting products are summarized in the context of genetic depositional realms proposed for the marine, Late Devonian Alamo Impact Event, central Great Basin, western USA.

Devonian limestone and dolostone formations are superbly exposed in numerous mountain ranges of southeastern Nevada. The Devonian is as thick as 1500 m there and reveals continuous exposures of a classic, long-lived, shallow-water carbonate platform. This field guide provides excursions to Devonian outcrops easily reached from the settlement of Ala...

Based on evaluation of past results and new research, we have partitioned the distribution of the Alamo Breccia in southeastern Nevada and western Utah into six genetic Realms that provide a working model for the marine Late Devonian Alamo Impact Event. Each Realm exhibits discrete impact processes and stratigraphic products that are enumerated her...

The present Central and Eastern High Atlas mountains of southern Morocco represent a short-lived Mesozoic rift, 500 100 km, associated with an ancient fracture zone between the Saharan Craton to the south and the smaller microplate mesetas to the north. A continental rift opened in the Upper Triassic, accumulating redbeds, evaporites and basalts. M...

Recent investigations on the Late Devonian Alamo Impact Event at Tempiute Mountain, Nevada, reveal that pervasive deformation in bedrock, breccia types, and the presence of high-pressure, shock-metamorphism in minerals and rocks suggest a scenario produced by impact-cratering processes.

About 370 million years ago, an object from space splashed down into the Devonian sea that bordered western North America, almost instantly blanketing much of southern Nevada and surrounding areas. Now known as the Alamo impact, the event resulted in one of the best-exposed and well-dated impact deposits and a full-scale physical model for understa...

The Alamo Breccia is a Late Devonian sedimentary layer as much as 135 m in thickness that is widespread over southern Nevada, USA. Direct evidence for an impact origin of the Alamo Breccia includes shocked quartz grains within the Breccia matrix and broken fragments of distinctive carbonate lapilli beds within the heterolithic Breccia clast populat...

Carbonate accretionary lapilli occur in the Late Devonian Alamo Breccia of south-central Nevada. They provide evidence for the extraterrestrial impact origin of the breccia, and help unravel the complicated events that formed it. The accretionary lapilli (Alamo lapilli) are concentrated in lapilli beds, and portions of the latter occur as reworked...

The Alamo Breccia is a carbonate rock breccia of Late Devonian age in southern Nevada. It is an anomalous sedimentary unit because it has the properties of a massive debris-flow and turbidity-current deposit that would be expected to occur in deep water, but is intercalated over much of its area with typical shallow-water carbonate-platform beds. T...

The sub-critical Alamo impact event, which occurred in a nearshore marine setting during the early Late Devonian (-367.2 million years ago), resulted in the formation of the spectacular and widespread Alamo megabreccia and relatedphenomena now exposed in southern Nevada, western USA. Although the exact site and dimensions of the Alamo impact crater...

The Alamo breccia is probably the most voluminous known outcropping carbonate megabreccia. It occupies -4000 km2 across 11 mountain ranges in southern Nevada, has an average thickness of -70 m, and contains a volume of 250+ km3. The breccia is a single bed, of early Frasnian (early Late Devonian) age, that formed in the wake of a giant slide that d...

A transmission electron microscope (TEM) study of quartz grains strongly implies that the Alamo breccia of southern Nevada resulted indirectly from a Late Devonian hypervelocity impact event. The Alamo breccia is perhaps the most voluminous marine carbonate megabreccia exposed on land. It covers ≈4,000 km2, averages ≈70 m thick, and contains...

The 80-m-thick Alamo Breccia within the Guilmette Formation is dated by a succession of conodont faunas as having been emplaced within a brief interval in the middle of the early Late Devonian (early Frasnian) punctata Zone. The breccia is underlain by peritidal to supratidal carbonate rocks containing a shallow-water (<10-m deep) pandorinellinid b...

Eight folded illustrations in pocket. Typescript (photocopy). Thesis (M. Sc.)--Colorado School of Mines. Includes bibliographical references (leaves 175-182).

Heterogeneous fills within similar subsurface systems are problematic for hydrocarbon exploration and production. Diagramming the stratigraphic and lithologic associations of the Torrey Canyon on photomosaics demonstrates the complexities. Many elements resemble fluvial fills; others are unique to the submarine setting. The basal (first-order) boun...

The Campos basin is situated in offshore southeastern Brazil. The Lagoa Feia is the basal formation in the stratigraphic sequence of the basin, and was deposited during rifting in an evolving complex of lakes of different sizes and chemical characteristics, overlying and closely associated with rift volcanism. The stratigraphic sequence is dominate...

The central and eastern High Atlas ranges of southern Morocco represent deposition in an Early to Middle Jurassic rift which first collected continental basalts, red beds, and evaporites. Carbonate deposition was initiated by a euxinic phase, followed by a mosaic of normal marine limestones and marls controlled by regional subsidence and local diff...

The central and eastern High Atlas ranges of southern Morocco represent deposition in an Early to Middle Jurassic rift which first collected continental basalts, red beds, and evaporites. Carbonate deposition was initiated by a euxinic phase, followed by a mosaic of normal marine limestones and marls controlled by regional subsidence and local diff...

The Campos basin is situated in offshore southeastern Brazil. The Lagoa Feia is the basal formation in the stratigraphic sequence of the basin, and was deposited during rifting in an evolving complex of lakes of different sizes and chemical characteristics, overlying and closely associated with rift volcanism. The stratigraphic sequence is dominate...

Carbonate platforms developed during the Early and Middle Jurassic on the margins of two seaways that are now exposed in the Middle and High Atlas, Morocco. The seaways occupied transtensional rifts, which, by Early Jurassic, had formed the segmented terrain on which the carbonate platforms established. Two episodes of platform development occurred...

The E-trending Piaui Basin off the N Brazilian continental margin is an Atlantic-type rifted basin. The stratigraphic and structural framework of the basin is interpreted as recording wrenching during separation of S America and Africa along the equatorial Romanche Fracture Zone. Superposition of rifting and wrenching resulted in a diverse set of s...

Field studies document an apparent eustatic control on facies patterns along a tectonically active margin. In the San Diego Embayment and northern Baja California, progradational-retrogradational shoreline sequences characterize Late Cretaceous and Eocene forearc stratigraphy. Extensive benthonic foraminifera and nannoplankton data provide control...

Heads of submarine canyons may occur anywhere on continental margins, from river mouths to continental slopes, producing a distinctive interface between shallow- and deep-marine environments. Inception of most canyons is subaerial, fluvially cut during lowered sealevel. Submarine mass flow also commences canyon formation. Submarine erosion shapes a...

Nine dives in the research submersible “Alvin” were made into Great Abaco Submarine Canyon to depths ranging from 1850 to 3666 m. Our observations indicate that the walls of this canyon are distinctly terraced, consisting of nearly vertical to overhanging rock cliffs and intervening, less steep sediment-covered slopes. The wall rock consists mostly...

Lower (?) to middle Eocene submarine canyon and associated inner fan deposits are well exposed along sea cliffs and in outcrops immediately inland in northern San Diego County, California. Seven environments are interpreted from these basin-margin deposits. These sub environments were recognized on the basis of bed forms, sedimentary structures, te...

Because borings represent taxa that had specialized morphological characteristics, they are useful for biological and paleobiological studies of both the borers and the substrates that they bore. Such structures also document the evolution of the borers and the boring habit, and thus borings can be geologic age indicators. Most borers discussed her...

We have studied two tidal lagoons, Mugu Lagoon in temperate California and Laguna Potosi in tropical Mexico. Critical for the sedimentology, ecology, and history of the lagoons is their inlet position and condition (open or closed). Sedimentation is tidally controlled when the inlets are open and negligible when they are closed.

Marine borers are nearly ubiquitous in the modern seabed. Their distinctive excavations provide abundant potential trace fossils, and their general erosional activities (bioerosion) are important factors in marine sedimentation and benthic ecology. Species of excavators include protozoans, plants, and animals. Those best studied are boring fungi, a...

The High Atlas Trough was formed during the early rifting of Africa and North America. Sedimentologic evidence indicates that subsidence of the trough was not accompanied by intense crustal deformation. The trough was a site of active sedimentation from Lower (Liassic) to Middle (Dogger) Jurassic time, and it contains a sequence of predominantly ca...

Distinctive biogenic sedimentary structures (trace fossils) in sedimentary rocks reflect the burrowing behavior of the animals that made them. Because the distribution of these animals is influenced by environmental factors such as water depth and substrate type, trace fossils have been used widely as paleoenvironmental guides. The massive, ungrade...

Cores recovered in the Caribbean Sea on JOIDES Leg 15 exhibit a superb assemblage of biogenic sedimentary structures. They are identified as distinctive trace fossils (ichnogenera) similar to those well-known from land-based stratigraphic sections. They represent the burrowing behavior of benthic animals living contemporaneously with sedimentation....

Rocks of the rim and upper walls of Scripps Submarine Canyon are intensely burrowed by marine invertebrates. Important excavators are bivalves, polychaetes, and sipunculoids whose activities culminate in a network of passageways and eventual disintegration of the rocks. In many localities erosion by animals is more important than erosion by physica...

Investigation of marine invertebrates that bore, rasp, scrape, or otherwise erode intertidal and subtidal outcrops of sedimentary rocks of the Pacific Coast suggests that they are very significant in attrition of submarine outcrops and in shaping the configuration of the seabed. Localities ranging from the intertidal zone to depths of 160 ft in sub...

The Central High Atlas Mountains occupy the site of an Early to Middle Jurassic east-west-trending seaway known as the Central High Atlas trough. Late Triassic-Early Jurassic continental rifting, combined with a transtensional structural regime, formed a system of pull-apart basins comprising the trough. A thick sequence of carbonate shelf-to-basin...

Biological attack of carbonate-cemented sandstones and mudstones (Cretaceous and Eocene ages) and semi-consolidated calcareous muds (Holocene age) were studied near La Jolla, southern California. Rocks were collected from the intertidal zone to a depth of 40 m using SCUBA. The deeper samples came from Scripps and La Jolla submarine canyons. In orde...

Living animals and empty shells have been collected in 55 samples from Mugu Lagoon, coastal southern California. The abundances and distributions of 73 molluscan species from the samples were studied in order to evaluate postmortem movement of shells. Although transportation is common across short distances within the lagoon, several lines of evide...

Graded bedding is common in intertidal sediments of Mugu Lagoon, California. This bedding is different from other graded sequences which have been described in that the coarsest size-grade at the top of the bed is the same size as the coarsest size-grade at the base; this size simply becomes less common upwards. The grading is accomplished by burro...

Prior to paleoecologic interpretation of fossils and their surrounding matrix, it is necessary to judge the adequacy of the geologic record to depict depositional site ecology. In a study of the ecology of Mugu Lagoon, several aspects of sediment and organism distribution are of interest. The aim of this work is to determine how well the Recent eco...

Shallow-water marine research is being conducted at the Pacific Missile Range Headquarters of the U. S. Navy, Point Mugu, California. This area was chosen because of its relatively natural state, ecologic variation, and large populations of invertebrates that may be preserved in the geologic record. Consent and aid for this project has been given b...