Palynology of Maastrichtian and Paleocene rocks, lower Colville River region, North Slope of Alaska

1988 ◽  
Vol 25 (4) ◽  
pp. 512-527 ◽  
Author(s):  
N. O. Frederiksen ◽  
T. A. Ager ◽  
L. E. Edwards
Keyword(s):  
Great Plains ◽  
Pollen Grains ◽  
North Slope ◽  
Northern Great Plains ◽  
Dinoflagellate Cysts ◽  
Spores And Pollen ◽  
The North ◽  
River Region ◽  
Colville River ◽  
North Slope Of Alaska

Outcrops of Maastrichtian rocks are rare on the North Slope of Alaska, and it is even more unusual to find outcrops of Maastrichtian and Paleocene age in the same vicinity. In general, Late Cretaceous and Paleogene rocks have not been well dated in published papers pertaining to northern Alaska. In this article, we describe palynomorph assemblages from 20 outcrop samples taken from nine localities along the lower Colville River and nearby areas. The latest Cretaceous palynomorph assemblages that are from marine rocks contain late Campanian or Maastrichtian dinoflagellate cysts; however, these cysts and other marine fossils are absent from the Tertiary samples, indicating that the Tertiary strata are nonmarine. Our latest Cretaceous and early Tertiary samples contain abundant spores and pollen grains and can be readily dated by reference to well-known pollen assemblages from the northern Great Plains and northwestern Canada. By dating each sampled outcrop, we can approximate the position of the Cretaceous–Tertiary boundary in the study area. Outcrop samples near the boundary are too widely separated stratigraphically to permit us to determine whether or not an unconformity exists at the boundary in the study area. Using spores, pollen grains, and dinoflagellate cysts, we date the samples below the Cretaceous–Tertiary boundary as being of approximately mid-Maastrichtian age and the samples above the boundary as being undifferentiated Paleocene in age. On the North Slope, as in regions to the east and south, the Maastrichtian pollen assemblages represent a different kind of flora and vegetation than the Paleocene assemblages. The Maastrichtian assemblages have moderately high diversities of angiosperm pollen taxa, most of which were probably insect pollinated. In contrast, the Paleocene assemblages have low diversities of angiosperm taxa, and many of these taxa were probably wind pollinated. Differences between the mid-Maastrichtian and Paleocene assemblages may have been caused at least in part by climatic changes but may also have been caused by the effects of a hypothesized bolide impact at the end of the Maastrichtian for which there is increasing evidence.

Palynostratigraphy and palaeoclimate of the Valanginian– Cenomanian subsurface succession in Hamza-1X well, Matruh Basin, Egypt

2020 ◽  
Vol 297 (2) ◽  
pp. 173-191 ◽  
Author(s):  
Ibrahim M. Ied ◽  
Sameh S. Tahoun ◽  
Walid A. Makled
Keyword(s):  
Age Determination ◽  
Pollen Grains ◽  
Point Of View ◽  
Western Desert ◽  
Dinoflagellate Cysts ◽  
Spores And Pollen ◽  
Dinoflagellate Cyst ◽  
The North ◽  
Assemblage Zone ◽  
Stratigraphic Succession

Diverse palynomorph assemblages of spores, pollen grains and dinoflagellate cysts have been yielded from the palynological analyses of 115 ditch cutting samples covering the Valanginian– Cenomanian succession encountered in Hamza-1X well, Matruh Basin, north Egypt. The complex sit- uations in the north Western Desert requires more revisited palynozones for better understanding of the subsurface successions therein. Consequently, the first downhole palyno-events will be very helpful in solving some issues concerning the age determination and correlation. Seventy palynomorph species (47 spores and pollen grains; 23 dinoflagellate cyst species) were identified from all the productive samples which used to divide the studied succession into numerous sporomorph and dinoflagellate biozones based on the last occurrence datum for the recovered marker taxa. Four sporomorph inter- val biozones and six dinoflagellate cyst interval biozones were differentiated from the same studied stratigraphic succession. The four sporomorph biozones are presented, in ascending order as follows: Aequitriradites spinulosus and Impardecispora apiverrucata Interval Zone (late Valanginian– early Barremian), Pilosisporites trichopapillosus I. Z. (late Barremian), Murospora florida I. Z. (early Aptian–late Aptian), and Elaterosporites klaszii I. Z. (early Albian– early Cenomanian). The seven dinoflagellate cysts biozones are Muderongia simplex I. Z. (late Valanginian–early Barremian), Pseudoceratium anaphrissum I. Z. (late Barremian– early Aptian), Cribroperidinium edwardsii I. Z. (early Aptian), Subtilisphaera perlucida I. Z. (late Aptian), Oligosphaerdium complex I. Z. (early– late Albian), Dinopterygium cladoides and Coronifera oceanica Assemblage Zone (early Cenomanian). From the palaeoclimatic point of view, the studied interval could be differentiated into two climatic intervals; the lower arid interval that comprises the Alam El Bueib Formation and dominated by the arid xerophyte elements like Sphaeripollenites and Classopollis. The upper humid interval represents the Alamein, Dahab, Kharita and Bahariya formations that is dominated by the humid hygrophyte elements, such as Murospora, Crybeolsporites, Elaterosporites, Afropollis and Deltoidospora.

Duck-bill dinosaurs (Hadrosauridae, Ornithischia) from the North Slope of Alaska

1987 ◽  
Vol 61 (1) ◽  
pp. 198-200 ◽  
Author(s):  
Kyle L. Davies
Keyword(s):  
Late Cretaceous ◽  
North Slope ◽  
First Report ◽  
The North ◽  
Family Level ◽  
Colville River ◽  
North Slope Of Alaska

Hadrosaur Bones have been found on the Colville River north of Umiat on the North Slope of Alaska. This find represents the first report of dinosaur bones in Alaska and their northernmost reported occurrence. The remains are not determinable below family level but are important, nonetheless, for interpretations of the paleoclimatology and paleobiogeography of the Late Cretaceous.

Dispersive noise removal in t-x space: Application to Arctic data

Geophysics ◽  
1988 ◽  
Vol 53 (3) ◽  
pp. 346-358 ◽  
Author(s):  
Greg Beresford‐Smith ◽  
Rolf N. Rango
Keyword(s):  
Signal To Noise Ratio ◽  
Noise Analysis ◽  
Noise Removal ◽  
North Slope ◽  
Frequency Bandwidth ◽  
The North ◽  
North Slope Of Alaska ◽  
Seismic Records ◽  
Time Offset ◽  
Undersampled Data

Strongly dispersive noise from surface waves can be attenuated on seismic records by Flexfil, a new prestack process which uses wavelet spreading rather than velocity as the criterion for noise discrimination. The process comprises three steps: trace‐by‐trace compression to collapse the noise to a narrow fan in time‐offset (t-x) space; muting of the noise in this narrow fan; and inverse compression to recompress the reflection signals. The process will work on spatially undersampled data. The compression is accomplished by a frequency‐domain, linear operator which is independent of trace offset. This operator is the basis of a robust method of dispersion estimation. A flexural ice wave occurs on data recorded on floating ice in the near offshore of the North Slope of Alaska. It is both highly dispersed and of broad frequency bandwidth. Application of Flexfil to these data can increase the signal‐to‐noise ratio up to 20 dB. A noise analysis obtained from a microspread record is ideal to use for dispersion estimation. Production seismic records can also be used for dispersion estimation, with less accurate results. The method applied to field data examples from Alaska demonstrates significant improvement in data quality, especially in the shallow section.

Cloud Properties over the North Slope of Alaska: Identifying the Prevailing Meteorological Regimes

2012 ◽  
Vol 25 (23) ◽  
pp. 8238-8258 ◽  
Author(s):  
Johannes Mülmenstädt ◽  
Dan Lubin ◽  
Lynn M. Russell ◽  
Andrew M. Vogelmann
Keyword(s):  
Time Series ◽  
Climate Model ◽  
North Slope ◽  
Test Cases ◽  
Synoptic Scale ◽  
Long Time Series ◽  
The North ◽  
Cloud Properties ◽  
North Slope Of Alaska ◽  
Long Time

Abstract Long time series of Arctic atmospheric measurements are assembled into meteorological categories that can serve as test cases for climate model evaluation. The meteorological categories are established by applying an objective k-means clustering algorithm to 11 years of standard surface-meteorological observations collected from 1 January 2000 to 31 December 2010 at the North Slope of Alaska (NSA) site of the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM). Four meteorological categories emerge. These meteorological categories constitute the first classification by meteorological regime of a long time series of Arctic meteorological conditions. The synoptic-scale patterns associated with each category, which include well-known synoptic features such as the Aleutian low and Beaufort Sea high, are used to explain the conditions at the NSA site. Cloud properties, which are not used as inputs to the k-means clustering, are found to differ significantly between the regimes and are also well explained by the synoptic-scale influences in each regime. Since the data available at the ARM NSA site include a wealth of cloud observations, this classification is well suited for model–observation comparison studies. Each category comprises an ensemble of test cases covering a representative range in variables describing atmospheric structure, moisture content, and cloud properties. This classification is offered as a complement to standard case-study evaluation of climate model parameterizations, in which models are compared against limited realizations of the Earth–atmosphere system (e.g., from detailed aircraft measurements).

An inverse relationship between moisture and grazing intensity in an arid mountain-basin system

2021 ◽  
pp. 030913332110600
Author(s):  
Jun Zhang ◽  
Xiao-zhong Huang ◽  
Jia-le Wang ◽  
Richard HW Bradshaw ◽  
Tao Wang ◽  
...  
Keyword(s):  
Arid Region ◽  
Influencing Factor ◽  
Regional Climate ◽  
Fungal Spores ◽  
Grazing Intensity ◽  
Pollen Grains ◽  
High Mountains ◽  
Spores And Pollen ◽  
The North ◽  
Basin System

Precipitation has been suggested as a crucial influencing factor in the primary productivity in arid and semi-arid regions, yet how moisture fluctuation in an arid mountain-basin system of the north Qinghai–Tibetan Plateau has affected human activities is poorly understood. Here, we reconstruct the variations of grazing intensity in high elevations and regional humidity based on independent and high-resolution records of Sporormiella-type coprophilous fungal spores and pollen grains in the same well-dated sediment core from Lake Tian’E in the western Qilian Mountains over the past 3500 years. We find that stronger grazing activity was associated with low regional effective moisture, and propose that the drier regional climate pushed people and their livestock into the mountainous areas. A notable exception was a reduction of human and grazing activities in arid region with high mountains during 380–580 CE caused by centennial-length dry and cold conditions. In addition, it is also noteworthy that intensified grazing activity occurred during 580–720 CE and after ∼1920 CE, corresponding to a warmer and wetter climate and diverse subsistence strategies with social developments in the lowlands of the Hexi Corridor. Our findings potentially provide a historical reference for understanding how ancient people adapted to the climate change in arid region with high mountains.

Underbalanced Drilling with Coiled Tubing: A Case Study on the Alaskan North Slope, Which Proves the Benefits of Drilling a Straight Hole

2021 ◽  
Author(s):  
Antoni Miszewski ◽  
Adam Miszewski ◽  
Richard Stevens ◽  
Matteo Gemignani
Keyword(s):  
Relative Effectiveness ◽  
Shallow Depth ◽  
North Slope ◽  
Coiled Tubing ◽  
The North ◽  
North Slope Of Alaska ◽  
Minimum Requirements ◽  
Bottom Hole Assembly ◽  
Alaskan North Slope ◽  
Future Work

Abstract A set of 5 wells were to be drilled with directional Coiled Tubing Drilling (CTD) on the North Slope of Alaska. The particular challenges of these wells were the fact that the desired laterals were targeted to be at least 6000ft long, at a shallow depth. Almost twice the length of laterals that are regularly drilled at deeper depths. The shallow depth meant that 2 of the 5 wells involved a casing exit through 3 casings which had never been attempted before. After drilling, the wells were completed with a slotted liner, run on coiled tubing. This required a very smooth and straight wellbore so that the liner could be run as far as the lateral had been drilled. Various methods were considered to increase lateral reach, including, running an extended reach tool, using friction reducer, increasing the coiled tubing size and using a drilling Bottom Hole Assembly (BHA) that could drill a very straight well path. All of these options were modelled with tubing forces software, and their relative effectiveness was evaluated. The drilling field results easily exceeded the minimum requirements for success. This project demonstrated record breaking lateral lengths, a record length of liner run on coiled tubing in a single run, and a triple casing exit. The data gained from this project can be used to fine-tune the modelling for future work of a similar nature.

Changes in tall shrub abundance on the North Slope of Alaska, 2000–2010

2018 ◽  
Vol 219 ◽  
pp. 221-232 ◽  
Author(s):  
Rocio R. Duchesne ◽  
Mark J. Chopping ◽  
Ken D. Tape ◽  
Zhuosen Wang ◽  
Crystal L.B. Schaaf
Keyword(s):  
North Slope ◽  
The North ◽  
North Slope Of Alaska ◽  
Tall Shrub
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