Middle Devonian to Lower Mississippian clastic depositional cycles, upper Kongakut River, northeastern Brooks Range, Alaska: preliminary results

10.14509/1435 ◽  
1990 ◽  
Author(s):  
A. V. Anderson
Keyword(s):  
Middle Devonian ◽  
Brooks Range ◽  
Preliminary Results ◽  
Depositional Cycles

A new species of Droharhynchia (Brachiopoda) from the lower Middle Devonian (Eifelian) of west-central Alaska

1994 ◽  
Vol 68 (6) ◽  
pp. 1235-1240 ◽  
Author(s):  
Mary E. Baxter ◽  
Robert B. Blodgett
Keyword(s):  
New Species ◽  
Middle Devonian ◽  
The Arctic ◽  
Geographic Proximity ◽  
Brooks Range ◽  
West Central ◽  
Arctic Alaska ◽  
Northern Alaska ◽  
A New Species

A new species of the genus Droharhynchia Sartenaer is established from lower Eifelian strata of west-central Alaska and the northwestern Brooks Range of Alaska. Droharhynchia rzhonsnitskayae n. sp. occurs in the Cheeneetnuk Limestone of the McGrath A-5 quadrangle, west-central Alaska, and the Baird Group of the Howard Pass B-5 quadrangle, northwestern Alaska. These occurrences extend the lower biostratigraphic range of both the genus and the subfamily Hadrorhynchiinae into the Eifelian. They also suggest close geographic proximity of the Farewell terrane of southwestern and west-central Alaska and the Arctic Alaska superterrane of northern Alaska during Devonian time.

scholarly journals Supplemental Material: Ulungarat Basin: Record of a major Middle Devonian to Mississippian syn-rift to post-rift tectonic transition, eastern Brooks Range, Arctic Alaska

2021 ◽  
Author(s):  
A.V. Anderson ◽  
K.E. Meisling
Keyword(s):  
Middle Devonian ◽  
Depositional Environments ◽  
Reference List ◽  
Brooks Range ◽  
Tectonic Transition ◽  
Arctic Alaska ◽  
Age Constraints

<div>Describes the organization, sedimentology, and depositional environments of the Ulungarat Basin succession including description of type sections of the Ulungarat and Mangaqtaaq formations. Table S1 documents published fossil and radiometric age constraints used to construct the mid-Paleozoic tectonostratigraphic chart (Fig. 12), including basis for age assignment and list of source references. A reference list of all sources cited in Table S1 is included.<br></div>

scholarly journals Supplemental Material: Ulungarat Basin: Record of a major Middle Devonian to Mississippian syn-rift to post-rift tectonic transition, eastern Brooks Range, Arctic Alaska

2021 ◽  
Author(s):  
A.V. Anderson ◽  
K.E. Meisling
Keyword(s):  
Middle Devonian ◽  
Depositional Environments ◽  
Reference List ◽  
Brooks Range ◽  
Tectonic Transition ◽  
Arctic Alaska ◽  
Age Constraints

<div>Describes the organization, sedimentology, and depositional environments of the Ulungarat Basin succession including description of type sections of the Ulungarat and Mangaqtaaq formations. Table S1 documents published fossil and radiometric age constraints used to construct the mid-Paleozoic tectonostratigraphic chart (Fig. 12), including basis for age assignment and list of source references. A reference list of all sources cited in Table S1 is included.<br></div>

scholarly journals Supplemental Material: Ulungarat Basin: Record of a major Middle Devonian to Mississippian syn-rift to post-rift tectonic transition, eastern Brooks Range, Arctic Alaska

2021 ◽  
Author(s):  
A.V. Anderson ◽  
K.E. Meisling
Keyword(s):  
Middle Devonian ◽  
Depositional Environments ◽  
Reference List ◽  
Brooks Range ◽  
Tectonic Transition ◽  
Arctic Alaska ◽  
Age Constraints

<div>Describes the organization, sedimentology, and depositional environments of the Ulungarat Basin succession including description of type sections of the Ulungarat and Mangaqtaaq formations. Table S1 documents published fossil and radiometric age constraints used to construct the mid-Paleozoic tectonostratigraphic chart (Fig. 12), including basis for age assignment and list of source references. A reference list of all sources cited in Table S1 is included.<br></div>

scholarly journals Preliminary results of mapping in the Caledonian rocks of Canning Land and Wegener Halvø, East Greenland

1972 ◽  
Vol 48 ◽  
pp. 21-38
Author(s):  
R Caby
Keyword(s):  
Structural Geology ◽  
Middle Devonian ◽  
Igneous Rocks ◽  
The West ◽  
East Greenland ◽  
Preliminary Results ◽  
Geological Map ◽  
Coherent Picture

The pre-Middle Devonian sediments and igneous rocks of Canning Land and Wegener Halvø (120 km2) were remapped in detail at a scale of 1:50 000 (map 2) during eight weeks of excellent weather in the summer of 1971. This area includes fragments of Caledonian superstructure bounded to the west by Middle Devonian clastics and the Mesozoic terrain of Jameson Land. Canning Land and Wegener Halvø have previously been investigated by Nordenskjold (1907), who gave the first geological map, Noe-Nygaard (1937), who carried out petrographical investigations on the igneous rocks, and Butler (1948), who presented a coherent picture of the stratigraphy and structural geology and a detailed map.

scholarly journals Taphofacies and bioevents in marine sequences of the Appalachian Basin Middle Devonian

1992 ◽  
Vol 6 ◽  
pp. 35-35
Author(s):  
Carlton E. Brett ◽  
Gordon C. Baird
Keyword(s):  
Sea Level ◽  
Middle Devonian ◽  
Taxonomic Composition ◽  
Black Shales ◽  
Low Energy ◽  
Guild Structure ◽  
Hamilton Group ◽  
Species Evolution ◽  
Depositional Cycles ◽  
Tectonic Origin

The Middle Devonian (Givetian) Hamilton Group is composed of widespread, time-stratigraphic, discontinuity-bounded depositional cycles which correspond to sequences and sub-sequences. Not only do recurrent lithofacies and biofacies units correlate predictably with given parts of cycles, distinctive taphonomic features also correlate with appropriate parts of transgressive-, early highstand-, and late highstand (regressive) systems tracts within sequences. Transgressive systems tracts (TSTs) are marked by widespread, thin (0.5 to 3 m), winnowed, shelly sandstones or skeletal wacke- to grainstones. Bases are typically heavily burrowed with a distinctive firmground ichnofacies. Internally, the beds display mixtures of variably disarticulated and corraded skeletal fragments, especially pelmatozoan debris. Condensed intervals are typified by sharp diastemic contacts between TSTs and overlying maximum highstand shales. These surfaces of maximum starvation may have thin (centimeters) lags of phosphatic, concretionary, or pyritic diaclasts, bones and conodonts as well as corroded carbonate skeletal debris. Early highstand deposits are characterized by an alternation of discrete storm beds with mudstones which may yield exceptionally well-preserved faunas. Late highstand- and regressive taphofacies display greater evidence of sediment-shell disturbance by bioturbation and repeated storms. The decrease in accomodation space dictates sediment-bypass and mixing with increased evidence of skeletal disarticulation and shell abrasion.A recurring, and somewhat enigmatic phenomenon consists of widespread (to 100s of km) shell and reworked concretion layers, associated with diastems, which occur at the late highstand or early sea level-fall position within offshore, low energy mudstones. These “precursor beds” are sediment-starved lags, which mark abrupt shoaling events followed by a return to deeper-water deposits below the transition to lowstand conditions. These lags either represent the overprint of condensed smaller cycles superimposed on larger ones or they may record a fundamentally new, little-understood, process associated with abrupt sea level drop.Most of the typical Givetian “Hamilton fauna” appears abruptly in the second major sub-sequence (4th order cycle) of the Hamilton Group. The Hamilton fauna was partitioned into distinctive biofacies which were remarkably stable in terms of taxonomic composition, guild structure and relative abundance. These biofacies tracked favored environments and recur through 10 or more basinwide cycles (including sub-sequences) during some 6–7 my. Surprisingly, relative lowstands, represented by sequence-bounding unconformities, appear to have had very little disruptive influence on tracking Hamilton biotas. Very few species became extinct, immigrated, or underwent significant morphological change during the entire Givetian interval. Instead, both the initiation and termination of the Hamilton fauna correspond with major deepening events (Marcellus and Genesee transgressions) of combined eustatic/tectonic origin. In both cases, the major faunal changes (extinctions, immigrations, species evolution) appear to be associated with widespread anoxic black shales in condensed early highstands of sequences. Both of these correspond to global bioevents (Kacak-otomari and Pharciceras events) that have been related to climatic change. This observation suggests that the major transgressions may have been associated with widespread environmental restructuring.

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