William N. Krebs

• PhD
• n/a at Independent Researcher

Evidence of the Cambrian Explosion in the White Mountains, CA

The formation of lacustrine diatomite depends upon adventitious circumstances: the creation of lake basins, nutrient-rich water, and lack of clastic input. These conditions persisted for millions of years in western Nevada during the late Miocene but came to an end by the Pliocene. Quaternary diatomite did form in some pluvial lakes during glacial...

Fossil evidence indicates that modern assemblages of temperate nonmarine planktonic diatoms began near the middle/late Miocene boundary when the genus Actinocyclus, an important constituent of lacustrine planktonic diatom assemblages during the early to middle Miocene, was replaced by genera of the family Stephanodiscaceae. This floral turnover has...

Lacustrine Diatomites in the western USA----age, distribution, origins, and potential for future research.

Graphic correlation analysis of biostratigraphic data from wells drilled in Sabah and Sarawak reveals that their Upper Tertiary sections consist of numerous chronosequences that are separated by hiatuses (unconformities or condensed sections). These hiatuses converge and diverge and are highly variable in duration, but their timing and maximum dura...

Introduction Diatoms constitute an important rock-forming microfossil group. They evolved rapidly during the Cenozoic, and unlike other microfossils, diatoms are found in marine, brackish, and lacustrine sediments, and are thus useful for age dating and correlating sediments that accumulated in a variety of environments. Their fossil assemblages ar...

A multidisciplinary project on an archaeological site on the Mitchell River, which feeds into Choctawhatchee Bay on the Florida panhandle, was designed to understand human adaptations to a dynamic hydrological environment during the Middle and Late Archaic period (ca. 8000–3000 B.P.). Now in a freshwater environment, on a sandy terrace above the Mi...

Chronostratigraphic Chart of the Stratigraphy of Malaysia

Core data---Figures 1 and 2.

Recovery of diatoms in core from an estuary in Florida.

A New Chronosequence Stratigraphy for the Tertiary of Offshore Sabah and Sarawak, Northwest Borneo, Malaysia William N. Krebs PETRONAS Carigali Sdn Bhd Petronas Twin Towers, KLCC, 50088 Kuala Lumpur, Malaysia williamkrebs@petronas.com.my Unconformities and condensed sections are boundary events in sequence stratigraphy that represent discontinu...

Unconformities and condensed sections are boundary events in sequence stratigraphy that represent discontinuities in deposition. These events can be detected using chronostratigraphy. Unconformities, for example, represent periods of geologic time not preserved in the rock record---a hiatus. Condensed sections, however, are thin rock intervals whic...

A stratigraphic chart incorporating all major Cenozoic Basins in Malaysia was constructed by Petronas. This chart reflects the most recent interpretations of Malaysian stratigraphy and correlations of east and west Malaysia. Our goals are to generate a comprehensive chronostratigraphic chart and increase the success rate of hydrocarbon exploration...

A stratigraphic chart incorporating all major Cenozoic Basins in Malaysia was constructed by Petronas. This chart reflects the most recent interpretations of Malaysian stratigraphy and correlations of east and west Malaysia. Our goals are to generate a comprehensive chronostratigraphic chart and increase the success rate of hydrocarbon exploration...

A New Chronosequence Stratigraphy for the Upper Tertiary of Offshore Sabah, Northwest Borneo, Malaysia Graphic correlation analysis of biostratigraphic data from the Upper Tertiary of more than 70 wells in offshore Sabah, northwest Borneo, has revealed the presence of at least 13 major hiatuses (SBH10 to110) that separate 14 chronosequences (SBS10...

Graphic correlation, sequence stratigraphy of Sirte Basin, Libya

The graphic correlation methodology offers a unique process for ordinating and calibrating various vintages of historical paleontological data from the Sirt Basin. Integration of the findings from graphic correlation with other sequence stratigraphic and geological data offers a very good opportunity to resolve the sedimentary depositional history...

Oral, Everglades\Caribbean Diatoms Stratigraphic, palynologic, and diatom analyses of core samples collected from the Mitchell River floodplain of western Florida indicate that environmental changes during the last 7,200 years had an impact on human use of the estuarine resources. Sixteen Middle to Late Archaic archaeological sites are perched on t...

Graphic correlation technique applied to exploration and production in the Nile Delta and Gulf of Suez, Egypt.

Graphic correlation illustrates the relationship of rock sections to geologic time. A line of correlation (LOC) drawn through paleontological datums that have been calibrated to geologic time depicts this relationship. The LOC consists of oblique line segments separated by horizontal lines or "terraces." If not fault related, these terraces represe...

From its inception during the early Miocene, the Suez Rift has been dominated by marine sedimentation. New high-resolution biostratigraphic and sedimentologic analyses of synrift deposits have resulted in the recognition of late Burdigalian-early Langhian brackish water and lacustrine deposits in the Wadi Abu Gaada-Gebel Gushia area, Sinai Peninsul...

The stratal architechture of the Gulf of Suez can be discriminated on several different orders. There are the sequences that can be defined paleontologically: however, since biostratigraphically detectable lacunae can be caused by several different processes, graphic correlation time gaps do not always correlate to true depositional sequence bounda...

Paleontological data derived from well cuttings and outcrop sections shed light on the chronostratigraphy and sequence stratigraphy of Miocene syn-rift rocks in the Gulf of Suez (GOS), and magnetostratigraphy of Miocene outcrop sections enhances the resolution of correlations. Graphic correlation of microfossil datums reveals that the Neogene secti...

Paleontology has played a long and distinguished role in the petroleum industry. Traditionally, paleontology has been used for two main purposes: dating of sedimentary rocks and stratigraphic correlations. The primary method for achieving both objectives was the recognition of index fossils. Based on the observed ranges of these index fossils, the...

The establishment of a robust, paleontologically defined chronostratigraphic framework coupled with detailed facies analysis of outcrops resulted in the development of a sequence stratigraphic model for the Miocene synrift of the Gulf of Suez. Application of this model, along with 3-D seismic, has had a major impact on the ability to recognize stra...

A diverse and well preserved non-marine palynomorph assemblage consisting of pollen, spores and chlorococcalean algae was recovered from three outcrop localities of the Cocobeach Group, North Gabon Subbasin. The pollen/spore assemblages are dominated by Classopollis and Ephedripites and include Afropollis jardinus (Brenner) Doyle, Jardine and Doere...

Unconformity-bounded sequences within the Miocene strata of the Suez Rift reflect a complex interplay between tectonism and sea level fluctuations. Analyses of Miocene outcrops along the Sinai margin of the Gulf of Suez provide new insights into the sequence stratigraphy of this basin. The Miocene strata can be subdivided into seven major sequences...

Graphic correlation of paleontological data from wells and outcrops in the Gulf of Suez reveals that the Neogene section consists of at least eight biostratigraphic sequences (S10-S80) separated by graphic terraces (T00-T70) (geologic lacunae or hiatuses). Field analysis in the Sinai of terraces T00 to T30 and their associated fossil assemblages in...

This composite standard establishes a scaled biostratigraphic sequence that incorporates all the fossil occurrences usually reported in paleontological studies of the North Sea Paleogene. All relevant taxonomic groups are represented, including benthic and planktic foraminifera, siliceous microfossils (diatoms and radiolarians), calcareous nannopla...

Diatoms are golden brown algae (class Bacillariophyceae) whose cellular contents are enclosed between two valves or shells of silica. They are classified into groups with radial symmetry (centric diatoms) and axial symmetry (pennate diatoms). The latter are subdivided as raphid and araphid diatoms according to the presence or absence of raphes (sli...

In the Western US, 12 obligate freshwater species of Actinocyclus Ehrenberg are restricted to the early and middle Miocene. Maximum diversity (11 species) was attained during the early middle Miocene, before the appearance of obligate lacustrine genera of the gamily Thalassiosiraceae. Fossil lacustrine Actinocyclus spp. are found elwhere in the wor...

Species of the diatom genus Actinocyclus Ehrenberg were important constituents of lacustrine phytoplankton in the Western US during much of the early and middle Miocene (19-10 Ma). Similar and/or identical fossil Actinocyclus species are found elsewhere in the world, particularly in Eurasia, in Neogene lacustrine diatomaceous rocks. Ten new species...

The Zeit Formation is late Miocene (Tortonian) in age and accumulated in a variety of shallow marine, freshwater, and brackish water settings. In the central and southern portions of the Gulf of Suez, the Zeit Formation is unconformably overlain by Pliocene shallow water calcareous deposits known as the Ashrafi Formation, while in the northern part...

The oldest known freshwater diatoms in North America are middle Eocene in age. During the Tertiary, there have been four distinct planktonic diatom communities in temperate freshwater lakes of W North America: 1) Aulacoseira-pennate genera (Eocene-Oligocene), 2) Actinocyclus-Thalassiosira-Aulacoseira (early to middle Miocene), 3) Mesodictyon-Cyclot...

A three meters section of diatomite in the mostly siliciclastic Caleta Herradura Formation is exposed along the shore north of Antofagasta, Chile. This deposit is a lensoid erosional remnant conformably underlain by mudstone and sandstone and truncated upsection by an angular unconformity at the base of the La Portada Formation. The diatoms belong...

Three major stratigraphic units have been recognized in the basin (from oldest to youngest): Karroo Supergroup, the Red Sandstone, and the Lake Beds. These units have traditionally been assigned the following ages, respectively, based upon lithologic correlations: Permian-Triassic, Jurassic-Cretaceous, and Tertiary. Recently, microfloral assemblage...

Paleoecology of Upper Miocene and Pleistocene diatomites in western Nevada.

Neogene and Quaternary lacustrine diatomaceous deposits are numerous in the western United States, particularly in the Great Basin. Some of these sediments are interbedded with volcanic rocks that have been dated radiometrically or by the fssion track method. Fossil lacustrine diatom floras can thus be arranged in geochronological order. By this me...

Sea-ice microflora was collected from December 1971 to November 1972 from a variety of types of sea ice in the vicinity of Arthur Harbor, Anvers Island, Antarctic Peninsula. Sixty-seven identifiable species of diatoms, one silicoflagellate and several archaeomonads were recoverd from the ice. Of these, only 24 diatoms and the archaeomonads were con...

Late Cretaceous (Campanian-Maastrichtian) diatoms found in the Pierre Shale of Wyoming, Colorado and Kansas are pyritized and appear to represent the genera Actinoptychus, Coscinodiscus, Trinacria, Endictya? and Gladius? Three unidentifiable forms have been assigned morphotypes. This is the first description of diatoms from the Cretaceous of the we...

Phytoplankton standing crop was negligible during the winter, due to lack of sunlight, occasional sea ice cover, and instability of the water column. Cryophilic diatoms released during the spring melting of sea ice served as an inoculum for later phytoplankton blooms. The temporal distribution of phytoplankton standing crop during the austral summe...

Little is known of the seasonal ecology of the neritic antarctic diatom biocoenose or its preservation in sediment. The purpose of this work is to broaden our knowledge of this subject. The ecology of neritic diatoms was studied in Arthur Harbor, Antarctica during a fourteen month period beginning in December 1971 and ending in January 1973. During...

WHETHER or not life can exist far from the open sea beneath the permanent ice shelves of Antarctica is not known, but there are three opinions. (1) A biota cannot exist at all because of the absence of surface primary and secondary productivity1. (2) A biota exists but with specialisations unique to life in the absence of surface productivity and i...

Remarkable resemblance of the isopod Serolis to trilobites---an example of convergent evolution.

Planktonic foraminifera were recovered from Antarctic sea ice in high densities (up to 470,000/cu.m). The specimens came from the porous bottom of floating sea ice and were associated with the diatom community that lives in this habitat. They are juveniles and are difficult to identify with certainty, but are probably Globigerina pachyderma or G. q...