Late Cenozoic History Research Articles

The late Cenozoic diatom stratigraphy and paleolimnology of Tule Lake, Siskiyou Co. California

Lacustrine diatoms are diverse, well preserved and abundant in cores of lake sediment to 334 m depth near the town of Tulelake, Siskiyou County, northern California. The cores have been dated by radiometric, tephrochronologic and paleomagnetic techniques, which indicate a basal age of about 3 million years (Ma) and a nearly continuous depositional record for the Tule Lake basin for the last 3 million years (My). Fossil diatoms document the late Cenozoic paleolimnologic and paleoclimatic history for the northwestern edge of the Basin and Range Province. During the last 3 My, Tule Lake was typically a relatively deep, extensive lake. The Pliocene is characterized by a diatom flora dominated by Aulacoseira solida suggesting more abundant summer precipitation and warmer winters. Increases in ‘Fragilaria’ at 2.4 Ma and between 2.0 and 1.7 Ma imply cooler summers that correlate to glacial environments recorded elsewhere in the world.

Late Cenozoic glacial history of the Ross embayment, Antarctica

Knowledge of the Cenozoic terrestrial and marine glacial history of Antarctica has been developed through studies of on-land surface outcrops and subsurface drillcores; and through examination of drillcores and piston cores obtained from a variety of offshore marine geological settings. These field and laboratory endeavors have been a major target of the Antarctic earth science community for more than thirty years. The Ross Sea sedimentary basins, including the Byrd basin (West Antarctica), Wilkes and Pensacola basins (East Antarctica), and the Transantarctic Mountains provide significant data on the Cenozoic glacial record; a record that has been traced back to at least 38 Ma (close to the Eocene-Oligocene boundary). This paper reviews the Late Cenozoic history of the Transantarctic Mountains and flanking sedimentary basins with emphasis on the debate between the ‘stabilist’ view of Antarctic ice sheet history (see Clapperton and Sugden, 1990) and our favored multi-glacial dynamic ice sheet model.

Late Cenozoic tectonics of the northwestern San Bernardino Mountains, southern California

The late Cenozoic structural and stratigraphic history of the northwestern San Bernardino Mountains supports two distinct episodes of uplift, in late Miocene to earliest Pliocene and Quaternary time, that we hypothesize are related to movements on low-angle structures beneath the range. In this paper, we document the nature, distribution, and timing of late Cenozoic deformation and deposition in the northwestern San Bernardino Mountains, and we illustrate the neotectonic evolution of the area in a series of interpretive paleotectonic block diagrams. In the first episode of deformation, late Miocene to earliest Pliocene motion on the south-southwest-directed Squaw Peak thrust system disrupted drainage in pre-existing Miocene nonmarine basins and uplifted the western third of the present range to form the ancestral San Bernardino Mountains. Crystalline rocks of the San Bernardino Mountains were thrust southward across the present site of the San Andreas fault between 9.5 and 4.1 Ma, at a time when the San Gabriel fault was the active strand of the San Andreas transform system. We speculate that the Liebre Mountain crystalline block at the northern margin of the Ridge Basin may be the missing upper plate of the Squaw Peak thrust, now offset along the San Andreas fault. The second episode of deformation began with uplift of the northern plateau of the modern San Bernardino Mountains on north-directed, range-front thrusts in early Pleistocene time, between 2.0 and 1.5 Ma. Synchronous uplift of the northern plateau, recorded in early Pleistocene fanglomerates on the northwestern margin of the range, is interpreted to be the result of movement of a relatively coherent crustal block northward up a south-dipping detachment ramp beneath the central range. In middle Pleistocene time, activity on the northern range front began to wane, and the locus of uplift shifted to a narrow zone of arching and northward tilting adjacent to the San Andreas fault, which subsequently migrated rapidly northwestward along the San Andreas fault from the western San Bernardino Mountains into the northeastern San Gabriel Mountains. We attribute this pattern of deformation to the passage of a bulge or strike-slip ramp attached to the southwest side of the San Andreas fault at depth.

Late Cenozoic history and styles of deformation along the southern Death Valley fault zone, California

Late Cenozoic deposits in the southern Death Valley region have been offset ∼35 km by right-lateral, strike-slip faulting on the southern Death Valley fault zone since Miocene time. Virtually all slip took place prior to ∼1 m.y. ago along western traces of the fault zone. During the past 1 m.y., the eastern traces of the fault zone have been active and characterized by oblique slip, with a lateral component of only a few hundred metres. Movement along these eastern traces has formed normal faults and gentle-to-isoclinal folds that have uplifted fan gravel and lacustrine sediments as much as 200 m above the modern alluvial fan surface. Surveying of the longitudinal profile of the Amargosa River, which flows within the eastern traces of the fault zone, suggests that vertical deformation continues today. The 35 km of right-lateral offset, which is based on matching offset alluvial fan gravel with its source area, refines earlier estimates of 8 to 80 km of movement for the southern Death Valley fault zone, and it is consistent with the geometry of a pull-apart basin model for central Death Valley. Causes for the observed differences in the style and timing of movement of the eastern and western subzones are not well understood. The study area, however, is located a few kilometres north of the intersection of the southern Death Valley and Garlock fault zones. The Garlock fault zone changes its sense of movement from left-lateral strike-slip to east-vergent thrusting against the southern Death Valley fault zone. The resulting compression may have caused the shift in activity and the change in style of deformation along branches of the southern Death Valley fault zone.

Late Cenozoic History of the Pacific North-West: Interdisciplinary Studies of the Clarkia Beds of Northern Idaho.

Late Cenozoic History of the Pacific North-West: Interdisciplinary Studies of the Clarkia Beds of Northern Idaho.

Mt. Blanco revisited: Soil-geomorphic implications for the ages of the upper Cenozoic Blanco and Blackwater Draw Formations

Mt. Blanco, on the eastern edge of the Southern High Plains of Texas, contains stratigraphic features significant in interpreting the late Cenozoic history of the region and the vertebrate paleontology of the Great Plains; however, the stratigraphic relations are confused in the literature or are unreported. Mt. Blanco is the type locality for the Blanco Formation and the Blanco Local Fauna, which occurs throughout North America and is the type fauna for the Blancan Land Mammal Age in North America. Here also occur exposures of the Blackwater Draw Formation, an extensive (120,000 km/sup 2/) eolian sheet that is the surficial cover of the region and contains the 1.4 Ma Guaje Ash and several buried soils. A reexamination of the section shows that (1) the Blackwater Draw Formation, an eolian deposit, contains three well-expressed buried soils (5 YR hues, argillic horizons greater than or equal to 1 m thick, Stages III and IV calcic horizons) and the similar regional surface soil (Paleustalf); (2) the Guaje Ash is within the lower Blackwater Draw Formation but is separated from the Blanco Formation, a lacustrine unit, by about 1 m of sediment, including the lowest buried soil; and (3) the lowest buried soil showsmore » a Stage IV calcrete formed at the top of the Blanco Formation and the base of the Blackwater Draw Formation and probably took about 200 ka to form. These new data suggested that deposition of the type Blanco sediments may have ended by about 1.6 Ma or earlier. Since that time, the Blackwater Draw Formation has accumulated episodically; periods of nondeposition are characterized by landscape stability and pedogenesis.« less

Late Cenozoic History of Humboldt Basin, Cape Mendocino Area, California: ABSTRACT

Late Cenozoic History of Humboldt Basin, Cape Mendocino Area, California: ABSTRACT

Comparative Age of Grassland and Steppe East and West of the Northern Rocky Mountain

Given the taxonomic and biogeographic differences between dominant species in grasslands of the Great Plains and the palouse grasslands and steppe of the Pacific Northwest, it seems likely that the two biomes have had separate origins. Fossil leaf and seed floras and pollen data from east and west of the Rocky Mountain cordillera and pollen data from the cordillera area suggest that three distinct floristic provinces were in existence by the beginning of mid-Miocene (Barstovian) time. Montane conifer forest poor in genera typified the Rocky Mountain foothills and nearby basins, while mixed conifer-deciduous hardwood forest and Taxodium swamps rich in woody genera occurred in the Columbia Basin. On the Great Plains the Kilgore flora (Barstovian of Nebraska) indicates deciduous open forest and prairie dominated by species of eastern and southern affinities. Younger Neogene floras in the Pacific Northwest suggest that steppe and local grassland were beginning to be important in the Pliocene of the Pacific Northwest, while grasslands and open forest became widespread on the Great Plains somewhat earlier (late Miocene or Clarendonian-Hemphillian time). The persistence of mixed conifer and broad-leaved forest on the Columbia Plateaus suggests that this area was open to the west through about 8 Ma. Due to the increasing height of the Cascade Range and/or regional upwarping, the rain shadow east of the Cascades became increasingly effective after the Clarendonian. Many of the terrestrial herbaceous groups and some shrub taxa of xeric environments reported here from a variety of sites are unknown in the Paleogene and may have evolved during the Neogene. According to the regional pollen record, terrestrial herbs become more diverse in the late Neogene. Recent fossil evidence has helped substantiate that the grasslands and steppe west of the Continental Divide in the Columbia Basin area are about three million years (Ma) old, about ten million years younger than similar vegetation types east of the Divide in the Rocky Mountain foothills and in the Great Plains. Biogeographic differences between the two areas are reflected in species composition and in the dominant habits of grasses. Some climatic differences between 'east' and 'west' exist, but they do not seem sufficient to account for the vegetation contrasts. We propose that an examination of the Late Cenozoic history (Miocene to present) of the northern Rocky Mountains may help illuminate the nature of origins of the grassland and steppe east and west of the Divide. The region to the west of the Rocky Mountains, the Columbia Plateaus3, is endowed with some of the finest and best-documented Miocene leaf floras in North America, while the region to the east, the Rocky Mountain foothills and the Great Plains, have Mio-Pliocene deposits for which pollen, leaf, and seed data are now available. To understand the history of grassland and steppe development, be

Plant biogeography and the late Cenozoic history of New Zealand

Abstract Patterns of regional endemism, vicariance, and disjunction in New Zealand higher plants are reviewed. These are discussed in relation to the post-Oligocene history of the geology, climate, and vegetation. Previous explanations for such distribution patterns have ccntred on the disruptive effects of ice and severe climates during the Last Glaciation, and subsequent migration of plants from glacial refugia during the postglacial. It is concluded that these explanations arc largely inadequate. It is suggested that many endemic, vicariant, and disjunct plant distributions are related to the large-scale modification of the New Zealand land mass which has occurred as a result of active tectonism since the Oligocene. The more stable regions of New Zealand (in particular Northland, northwest Nelson, and Otago) have retained diverse floras partly as a result of retention of older elements of the flora which more radically altered areas (southern North Island, central South Island) have tended to lose. The...

Spatial and temporal variations in the Andean subduction zone

A comprehensive global study of the process of subduction of oceanic lithosphere has made it evident that a major role is played by the age of the subducted lithosphere. The age-dependence of subduction is of special interest in an understanding of the late Cenozoic history of the Andean subduction zone. Many of the complexities of this zone result from the peculiar circumstance that the zone is in transition from an early stage of consumption of old lithosphere (>70 Ma, producing deep earthquakes) towards the latest stage of consumption of young lithosphere (without deep earthquakes). This transition has induced an evolutionary pattern with significant temporal variations, notably changes in dip and length of the subducted slab. Moreover, the various segments of the South American subduction zone are in different stages of this evolution. In comparison with the other segments, the northern Chile segment is in the earliest stage and, therefore, shows a much closer resemblance to the ‘classic’ deep subduction zones in the Western Pacific than do other parts of the South American zone. A roughly N–S symmetry in development is found around northern Chile, with the Ecuadorian and southern Chilean (near 40–45°S) segments representing the latest stage. To a large extent the temporal and spatial variations in lithospheric age at the trench originate from the reorganization in plate configuration which started with the break-up of the Farallon plate into the Cocos plate and the Nazca plate at about 25 Ma.

Late Cenozoic History of Safford-San Simon and Bonita Creek Structural Basins, Graham County, Arizona: ABSTRACT

Sedimentary rocks of the interconnected Safford-San Simon (S-SB) and lower Bonita Creek (BCB) basins are separated into: (1) lower Miocene volcaniclastic conglomerate, (2) upper Miocene? to Pleistocene? Gila Conglomerate, and (3) Quaternary alluvium and surficial deposits. The volcaniclastic conglomerate is locally interbedded with andesite and 19-Ma ash-flow tuff in BCB and is part of the bed rock deposited prior to formation of structural basins by Basin and Range extensional tectonics. The Gila Conglomerate consists of more than 1,200 m (3,900 ft) of basin-fill sedimentary rocks. Where exposed, most of the lower units are locally derived alluvial-fan deposits. Upper units of the Gila (Pliocene to lower Pleistocene?) include lacustrine beds interbedded with deposits of low-gradient alluvial fan covering 730 km2 (280 mi2) from its apex at the mouth of Bonita Creek, southwestward across the width of the S-SB. Thick sequences of halite and gypsum penetrated in wells in the S-SB indicate playa deposits at depth. Red granite clasts in the fan deposits indicate that Bonita Creek had eroded headward to the upper BCB and captured streams draining the Point of Pines area. The youngest sediments are chiefly Quaternary alluvium deposited after the Gila River developed through-flowing drainage. The initial course of the Gila River was along the north side of the low-gradient fan. This course disrupted the depositional balance of streams draining the Pinaleno Mountains southwest of the S-SB and caused deposition of range-front alluvial fans 1 0 m (390 ft) thick. These fans were abandoned as the Gila River migrated to the center of the basin and are now spectacularly exposed as erosional remnants. End_of_Article - Last_Page 938------------

Influence of the Onion Creek salt diapir on the late Cenozoic history of Fisher Valley, southeastern Utah

The upper Cenozoic deposits in Fisher Valley, Utah, record a long history of deposition, deformation, and geomorphic changes related to movement of the Onion Creek salt diapir. Apparently, several pulses of salt flowed into the diapir between about 2–3 and 0.25 m.y. ago, and the diapir may still be active. Fisher Creek once headed in the igneous rocks of the La Sal Mountains and flowed along the present course of Onion Creek to the Colorado River. The rising salt diapir impeded the flow of ancestral Fisher Creek, causing deposition of more than 125 m of basin-fill sediments, and eventually diverted the creek down Cottonwood graben to the Dolores River about 0.25 m.y. ago. Onion Creek has eroded headward from the Colorado River, through both the diapir and the basin-fill sediments, and is about to capture Fisher Creek, restoring the original drainage course.

Soils and late Cenozoic history of the upper Wright Valley area, Antarctica

Abstract Within the small alpine valleys at the western end of the Asgard Range, between the Wright and Taylor Valleys, moraines are found which appear to be older than those previously described in the Wright and Taylor Valleys. These moraines have been placed in order of relative age by the weathering and amount of profile development in the soils found on them. The alpine valleys may have formed during the initial glaciation of Antarctica when the major glacial features of the topography were formed. Within these valleys there is evidence for at least two periods of glacial erosion and moraine formation, during which the Wright Valley was completely filled with ice. These episodes must therefore be older than the Wright Upper IV episode which occurred more than 3·7 million years ago Because of their isolation and lack of precipitation, the valleys have been little affected by subsequent glacial events, and the alpine glaciations recorded elsewhere in the Wright Valley have left only small deposits around snow-drift fed ice tongues. The glacial history of Antarctica between the full bodied stage of glaciation in mid-Miocene times and the late Pliocene Wright IV episode must have been quite complex. Traces of glacial events during this period may also be found in other localities high above present ice levels.

Pliocene-Pleistocene Diastrophism of Santa Monica and San Pedro Shelves, California Continental Borderland

Data from geophysical profiling and from jet and dart coring have been used to study the late Cenozoic history of the Santa Monica and San Pedro Shelves. Deformed strata commonly crop out on the outer shelf and consist chiefly of shale belonging to the Monterey Shale and the Repetto Formation (middle Miocene through lower upper Pliocene). In contrast, undeformed sands and silts, primarily beneath the inner shelf, represent the Pico and San Pedro Formations (uppermost Pliocene through middle Pleistocene) as well as unnamed upper Pleistocene and Holocene deposits. Together with the Palos Verdes Hills and the Lasuen Knoll, outer-shelf strata have been folded into five northwest-trending en echelon anticlinoria. One anticlinorium is in a structural depression directly north of Canyon and has been buried beneath undeformed sediments. This depression facilitated initial development of the canyon during late Pleistocene time. An east- ortheast-striking termed the Redondo Canyon fault, separates the platform anticlinorium from the Palos Verdes Hills anticlinorium. Formation of the anticlinoria and the Canyon fault is attributed to convergent dextral shear along the northwest-striking Palos Verdes fault after early Pliocene time. Although displacement along the Palos Verdes fault has continued in San Pedro Bay through late Pleistocene time, the absence of large vertical separation in the upper 300 m of strata in Santa Monica Bay north of the platform anticlinorium indicates that the fault has been relatively inactive there at least since the beginning of late Pleistocene time. These observations infer that the late Quaternary uplift of the Palos Verdes Hills was decoupled from the Santa onica shelf along the Canyon and may have occurred because the Santa Monica Shelf restrained the relative northwestward movement of the Palos Verdes Hills block. It is suggested that late Pliocene and early Pleistocene diastrophism in the California continental borderland was characterized by convergent dextral shear accompanied by en echelon folding. This contrasts with the middle and early late Miocene history of widespread faulting and large lateral displacements proposed by other investigators. The transition in the style and locus of deformation between 12 and 3 m.y.B.P. may be related to a change in the orientation of the transform boundary between the North American and Pacific plates, changing slip rates along the San Andreas and, possibly, differences in slip rates along the San Andreas north and south of the Transverse Ranges.

Delimitation of Weathering Zones in the Fiord Area of Eastern Baffin Island, Canada

Research Article| May 01, 1974 Delimitation of Weathering Zones in the Fiord Area of Eastern Baffin Island, Canada STEPHEN J. BOYER; STEPHEN J. BOYER 1Institute of Arctic and Alpine Research; and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80302 Search for other works by this author on: GSW Google Scholar DAVID R. PHEASANT DAVID R. PHEASANT 2Department of Geological Sciences, Southern Methodist University, Dallas, Texas 75275 Search for other works by this author on: GSW Google Scholar Author and Article Information STEPHEN J. BOYER 1Institute of Arctic and Alpine Research; and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80302 DAVID R. PHEASANT 2Department of Geological Sciences, Southern Methodist University, Dallas, Texas 75275 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1974) 85 (5): 805–810. https://doi.org/10.1130/0016-7606(1974)85<805:DOWZIT>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation STEPHEN J. BOYER, DAVID R. PHEASANT; Delimitation of Weathering Zones in the Fiord Area of Eastern Baffin Island, Canada. GSA Bulletin 1974;; 85 (5): 805–810. doi: https://doi.org/10.1130/0016-7606(1974)85<805:DOWZIT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Three weathering zones have been delimited in the Maktak/Narpaing Fiord area on the basis of data collected during field reconnaissance studies. A detailed sampling of weathering characteristics in Maktak Fiord and subsequent use of character analysis and discriminant analysis techniques supports the trizonal classification. The best combination of weathering characteristics for future use in statistical delimination of weathering zones was tested by multiple stepwise discriminant analysis procedures.Weathering zones appear to have a regional distribution. The zones are stratigraphic units that can be used as a framework upon which a late Cenozoic history of the Cumberland Peninsula and perhaps eastern Baffin Island could be constructed. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Response : A Route to Late Cenozoic Temperature History?

<i>Response</i> : A Route to Late Cenozoic Temperature History?

A Route to Late Cenozoic Temperature History?

A Route to Late Cenozoic Temperature History?

A Route to Late Cenozoic Temperature History?

A Route to Late Cenozoic Temperature History?

Arctic Ocean Ice Cover and Its Late Cenozoic History

Foraminifera abundance patterns and accompanying sediment analysis from Arctic Ocean sediment cores are useful tools in paleoecologic interpretations. In the Brunhes interval, there are at least two abundance peaks of Foraminifera; one, representing present conditions, in the top part of all cores, and the other near the Brunhes-Matuyama boundary (700,000 yrs B.P.). In addition, many cores show a continual fluctuating abundance pattern throughout the Brunhes interval. Cores with older age sediment have two additional Foraminifera abundance peaks, both in the Maruyama. The younger is in the middle part of the Maruyama and the older is near the time of the Olduvai Event in the early part of the Matuyama. Study of the oldest age sediment available (middle Pliocene) confirms that Foraminifera never have been more abundant in the Arctic Ocean than they are today. Therefore, the ice-covered conditions of the present are taken to represent the warmest conditions necessary to explain other older abundance peaks in the cores. If carbonate solution is eliminated as an explanation, the intervals of few or no Foraminifera must represent conditions quite different from those represented by the abundance peaks and the present. The equilibrium ice conditions of the modern Arctic Ocean could be altered by minor atmospheric variations. Thicker ice could form rather quickly and rather simply and this could upset plankton productivity. Thicker ice could also prevent a free accumulation of coarse detritus and erratics such as accumulate in the Arctic Basin today. These sediment types generally are most abundant during times of abundant Foraminifera deposition and are rare in the intervals during which few or no Foraminifera were deposited. These factors considered together lead to the theory that the Arctic Ocean has been frozen since at least the middle Pliocene and that the most significant change in the Arctic ice has been in its thickness. Thicker ice restricted photosynthesis and Foraminifera productivity. Times of thinner ice with conditions more like those of the present are represented by abundance peaks of Foraminifera and concentrations of glacially rafted material. None of the patterns of Foraminifera abundance or glacially rafted material show good correlation with the classical continental glacial stages. Continental glaciers advanced and retreated in the northern hemisphere while the Arctic ice-cover remained relatively stable. There would be important ecologic, economic, and political problems if the Arctic Ocean were to become ice-free. The historical evidence does not support the idea that a renewed pattern of Pleistocene glaciation would be one of the problems, however.

Terraces and Pediment-Terraces in the Southwest: An Interpretation

Both fluvial terraces and pediment-terraces (defined as pediment-like surfaces cut in soft rock) have been observed to occur together, within the same drainage basins, throughout the Southwest. Despite their significance for resolving the genesis of land forms and the late Cenozoic history of the Southwest, few detailed studies regarding them have been reported. They are commonly explained as the product of tectonic uplift during the Pleistocene. Some have attributed terraces and pediment-terraces to climatic changes, but few agree on the specific causes. No prior study explicitly treats the mutual occurrence of terraces and pediment-terraces. In the Tonto Basin of central Arizona are seven distinct terraces and five pediment-terraces that range from 20 to nearly 1,000 ft above the present flood plain of Tonto Creek. These two types of surfaces do not grade into one another, but are products of different erosional episodes. Tectonic hypotheses do not account for either the regional distribution of pediment-terraces or their alternation with fluvial terraces. Therefore we favor a climatic origin, and suggest that pediment-terraces are products of arid episodes and terraces are products of more humid episodes. They probably correlate with interpluvials and pluvials of the Pleistocene.