The Campbellton Formation, New Brunswick, Canada: paleoenvironments in an important Early Devonian terrestrial locality
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Abstract:
Strata of the Campbellton Formation, nearly 1 km-thick and known for its diverse fossil assemblage of early plants, arthropods, and fish, can be divided into six facies associations: (1) restricted lacustrine, (2) marginal lacustrine, (3) near-shore lacustrine, (4) coastal-deltaic, (5) sandy to gravelly alluvial plain, and (6) gravelly proximal alluvial environments. Lacustrine deposits with restricted circulation, due to depth or stagnation, are fine-grained with preserved organic material. The marginal lacustrine association consists of massive siltstone and very fine sandstone, interbedded with conglomerate. The latter are interpreted to have shed from older volcanic units forming the basin walls. The near-shore lacustrine association is characterized by rippled sandstone with microbialites. Alluvial strata include interbedded imbricate to nonimbricate conglomerate, trough cross-stratified sandstone, and barren to plant-bearing siltstone. Rare exposures of thickly bedded imbricate to weakly imbricated cobble–boulder conglomerate with sandy plant-bearing lenses are interpreted as products of hyperconcentrated debris flows. In the western belt, a braided-fluvial system had paleocurrents flowing WNW. Coastal-deltaic deposits west of the fluvial outcrops, containing aquatic vertebrates and invertebrates, had paleocurrents flowing ESE, suggesting a confined body of fresh or brackish water. In lower parts of the eastern belt, lacustrine facies are prevalent, representing a large open lake. Alluvial facies dominate upper parts of the formation, representing an eastward-flowing axial braided river system, with proximal alluvium shed transversely from the basin margins. Although most strata have a volcanic provenance, only one outcrop in the lacustrine beds shows evidence of active volcanism during deposition of the Campbellton Formation.Keywords:
Siltstone
Conglomerate
Outcrop
Cobble
Alluvial fan
Overbank
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Siltstone
Conglomerate
Phyllite
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Abstract Quartzite cobble and boulder conglomerates are widely scattered through the Paleocene-early Eocene stratigraphic record of the western Bighorn Basin, Wyoming. Paleocurrent indicators, in conjunction with the timing of tectonic events in northwest Wyoming, demonstrate that accumulation of these conglomerates was instigated by episodic orogenic activity in the Jackson Hole area, over 100 km west of the Bighorn Basin. Deformation resulting from intrabasinal tectonic pulses also controlled the periodicity of gravel influxes to the Bighorn Basin as well as the depositional settings in which the quartzite conglomerates formed. Different modes of deposition are distinguished on the basis of conglomerate outcrop pattern and distinctive suites of depositional facies. The oldest (earliest Paleocene) conglomerate is dominated by massive or horizontally bedded cobble conglomerate that was deposited by a braided river that flowed through an area of dissected, upturned strata along the western margin of the Bighorn Basin. Unusually thick sets of planar cross-stratified conglomerate are also common and are attributed to deep and prolonged floodstages, reflecting humid conditions and valley confinement of the stream system. In contrast, the youngest (early Eocene) conglomerate, though dominated by massive or horizontally bedded conglomerate, lacks abundant large scale cross-bedded conglomerate and was deposited on an extensive braidplain. Facies change markedly over short distances due to lateral spread of flow on the braidplain and decrease in paleoslope toward the Tertiary structural axis of the Bighorn Basin.
Conglomerate
Cobble
Paleocurrent
Outcrop
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This paper defines three Upper Cretaceous formations exposed in and near San Diego, California. The lowest, which consists of boulder conglomerate, is the previously named Lusardi Formation; the intermediate, which consists of siltstone and sandstone, is the Point Loma Formation (new name); and the uppermost, which consists of sandstone and conglomerate, is the Cabrillo Formation (new name). Together these constitute the Rosario Group, redesignated from its former rank as a formation. Eight partly intertonguing Eocene formations also are defined. Of these, six have new names and two are former members raised in rank to formational status. The lowest of the Eocene formations is the Mount Soledad Formation (new name), a marine conglomerate and sandstone unit occurring in th western part of the area. Above and northeast of the Mount Soledad Formation are the laterally equivalent Delmar Formation and Torrey Sandstone (both raised here from member to formational rank) and the Ardath Shale (new name). The Delmar Formation is an oyster-bearing sandy claystone, the Torrey Sandstone is a massively crossbedded sandstone, and the Ardath Shale is a fossiliferous silty shale. Overlying and partly intertonguing with these formations is the Scripps Formation (new name), composed of sandstone, siltstone, and conglomerate, and overlying the Scripps is the chiefly nonmarine Friars Formation (new name), which consists of sandstone and sandy claystone. All these Eocene rocks were formerly included in the La Jolla Formation, which is here elevated to group status. The remain ng part of the Eocene section in the San Diego area, above the La Jolla Group, was formerly called the Poway Conglomerate and is here elevated to group status, and two new formations are designated in its lower part. The lower, which consists of cobble conglomerate, is the newly named Stadium Conglomerate; the upper, which consists chiefly of marine sandstone and siltstone, is the newly named Mission Valley Formation.
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Abstract The Tertiary sequence in Coal Creek reported by Mason (1948) was recently re-examined and a thick greywacke conglomerate, not recorded by Mason, was found to form the apparent base of the sequence (Fig. 2a). The conglomerate is over 300 ft thick, consists predominantly of well rounded but poorly sorted, pale-green leached greywacke pebbles commonly ½ to 1 in. across, and contains several thin beds of fine sandstone and dark-grey carbonaceous siltstone up to 1 ft thick that yielded microfloras of late Cretaceous age (samples, S91/523, L2877; S91/524, L2878). Mr D. J. McIntyre, N.Z. Geological Survey (pers. comm.), places the age as probably Mata Series and definitely not older than Raukumara Series or younger than Mata Series.
Conglomerate
Siltstone
Sequence (biology)
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The stratigraphic succession of the rocks of the Nakatu district is as follows: (9) Alluvium (8) Kanto volcanic ash (7) Terrace deposite (6) Sioda pumiceous sandstone and mudstone (5) Otuka tuffaceous siltstone (4) Takadabasi sandstone and conglomerate (3) Kanzawa alternation of sandstone and siltstone (2) Kosawa sandstone and conglomerate (1) Kobotoke group Nakatu super-formation 1) Many fossil shells are allochthonous in the Kosawa and Kanzawa formations, but only a few are so in the other formations., 2) The Kosawa, Kanzawa and Takadabasi formations were deposited in the euneritic zones, but the Otuka and Sioda formations were formed in the mesoneritic or subneritic zones., 3) During the deposition of the Nakatu super-formation, the Kurosio current was more predominant than the Oyasio, except at several horizons., 4) At the beginning of the deposition of the Nakatu super-formation, the bottom-current were strong and at the end it became weak., The direction of the current is interpreted as S, SW, W, or WNW.,
Conglomerate
Siltstone
Deposition
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Summary A mid-Cretaceous cobble conglomerate in the Beer district, south Devon, is interpreted as a Lower Cenomanian beach deposit.
Cobble
Conglomerate
Cenomanian
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Abstract The Parke Siltstone, Hermannsburg Sandstone and Brewer Conglomerate of the Late Devonian to Early Carboniferous Pertnjara Group in the Amadeus Basin, central Australia, have been subdivided into eight new members. The Parke Siltstone at the base is an alternating sequence of siltstone and sandstone occurring in the central part of the basin. It has been subdivided into the following members in ascending stratigraphic order—Deering Siltstone Member, Harajica Sandstone Member, Dare Siltstone Member, and Amulda Member. The overlying Hermannsburg Sandstone is the most extensive formation of the Pertnjara Group and the following members have been recognised—the quartz-rich Ooraminna Sandstone and Owen Springs Sandstone Members, both of localised extent, and the Ljiltera Member which is more widespread and forms the upper pebbly part of the formation. The Undandita Member has been erected to distinguish the interbedded sandstone and conglomerate in the upper part of the Brewer Conglomerate from the massive conglomerate underlying it. The relationship between the three formations is conformable and transitional over most of the basin except around local structures mainly on the northern margin of the basin. The lateral relationship between the Pertnjara and Finke Groups is discussed in terms of interdigitating facies. A brief summary of the structural features of the Amadeus Basin is given and the effects of the Rodingan, Pertnjara, and Henbury Movements and the Alice Springs Orogeny on sedimentation of the Pertnjara Group are discussed in terms of syntectonic deposition.
Siltstone
Conglomerate
Devonian
Calcarenite
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Four new formation names are used herein for hitherto undescribed or inadequately described rocks in the Jackson Hole region, Teton County, Wyoming: The name Harebell formation is used for a 5,000-foot succession of quartzite pebble conglomerate, olive-drab to gray sandstone, drab-colored siltstone, claystone, and shale of Late Cretaceous age unconformably overlying older Cretaceous rocks and unconformably overlain by Paleocene and younger Tertiary rocks. The name Colter formation is used for a 7,000-foot sequence of white, gray, green, and brown, water-laid basic pyroclastic conglomerate, tuff, sandstone, and claystone of middle Miocene age, unconformably overlying all older rocks and unconformably overlain by rocks of middle Pliocene age. The name Teewinot formation is used for 5,000 feet or more of white limestone, pumicite, tuff, claystone, diatomite, and conglomerate of middle Pliocene age, unconformably overlying all older rocks and unconformably overlain by strata of late Pliocene or Pleistocene age. The name Bivouac formation is used for 1,000 feet of poorly lithified conglomerate interbedded with less amounts of sandstone, siltstone, claystone, pumicite, and welded rhyolite tuff of late Pliocene or Pleistocene age, unconformably overlying rocks of middle Pliocene age, and unconformably overlain by glacial and integlacial deposits of Pleistocene age.
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The red beds of the northern Heyuan Basin (Guangdong Province, China) are more than 4,000 m thick.Based on the lithological characters, in ascending order these beds are divided into the Dafeng Formation, Zhutian Formation, and Zhenshui Formation of the Nanxiong Group, Shanghu Formation and Danxia Formation. The Nanxiong Group with relatively mature coarse clastic rocks attains about 2 940 m in thickness. The Dafeng Formation is 837 m thick,consisting of conglomerates and sandy conglomerates; the Zhutian Formation, which is 1,200 m thick, consists of purplish red sandstone with gravels, poorly sorted sandstone, feldspathic quartzose sandstone banded granular conglomerate,siltstone, and sandy mudstone. The Zhutian Formation is rich in calcareous concretions. Heyuannia (Oviraptoridae) and turtle fossils were found in this formation. The Zhenshui Formation deposited to a thickness of 900 m consists of coarse sediments, including granular conglomerate, and gravelly sandstone with well developed cross-beddings; the Shanghu Formation, which is 820 m thick, consists of purplish red granular conglomerate coarse sandstone intercalated with fine siltstone; the Danxia Formation characterized by the Danxia landform is composed of coarse clastic gravels and sandy gravels. The lower part of the Nanxiong Group whence dinosaur eggs and derived oviraptorosaurs come, belongs to the Late Cretaceous. No fossils are found in the Shanghu Formation or the Danxia Formation, but their stratigraphic order of superposition on the Nanxiong Group clearly shows their younger age.
Siltstone
Conglomerate
Red beds
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