Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico.
{"title":"Supplemental road log 1: From intersection of Piedra Lumbre road and NM-197 to Star Lake and Pueblo Alto Trading Posts","authors":"E. C. Beaumont, Gretchen K. Hoffman","doi":"10.56577/ffc-43.65","DOIUrl":"https://doi.org/10.56577/ffc-43.65","url":null,"abstract":"Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico.","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124894373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Williamson, S. Lucas, A. Hunt, L. Smith, B. Kues
{"title":"Second-day road log: From Cuba to Counselor, Lybrook, Nageezi, Barrel Springs, Fossil Forest, Blanco Trading Post and return to Cuba","authors":"T. Williamson, S. Lucas, A. Hunt, L. Smith, B. Kues","doi":"10.56577/ffc-43.33","DOIUrl":"https://doi.org/10.56577/ffc-43.33","url":null,"abstract":"","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122027414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Uppermost Cretaceous and Paleogene terrestrial strata in the San Juan Basin record the local disruption and partitioning of the Cretaceous foreland basin by Laramide-aged up lifts. The importance of unconformities within the stratigraphic section, wh ich includes the Fruitland Formation, Kirtland Shale and Ojo Alamo Sandstone, and the nature of the Cretaceous/Tertiary boundary has been controversial, especially in the southeastern San Juan Basin near the Nacimiento uplift . Surface and subsurface mapping has recent ly identified an unconformity-bound sand-rich flu vial unit, here referred to as "unit B," between the Fruitland/ Kirtland and Ojo Alamo formations, which may explain some of the earlier mapping problems . " Unit B" on Mesa Portales contains distinct channel sandstones and interbedded siltstones and mudrocks that show mottling and oxidation profiles typ ical of a high energy fluvial system with well-drained floodplains. Paleocurrent measurements clearly show that deposition of much of "unit B" was related to north-to-south paleoslopes. Detrital lithologies indicate that sandstones of "unit B" and the Ojo Alamo Sandstone were derived from similar bedrock lithologies . North-to-south directed channels, parallel to the Nacimiento up lift, were responsible for depositing "unit B, " the Ojo Alamo Sandstone, the upper Nacimiento Formation and the Cuba Mesa Member of the San Jose Formation . Maintenance of the position of channels parall el and adjacent to the Nacimiento uplift represents continued syntectonic sedimentation in this region from the Late Cretaceous through the early Eocene . INTRODUCTION Uppermost Cretaceous and Paleogene terrestrial strata in the San Juan Basin were deposited during northeast deltaic progradation following withdrawal of the Cretaceous seaway and subsequent Laramide (Late Cretaceous-Eocene) uplift within the southern Rocky Mountains (Baltz, 1967; Fassett and Hinds, 1971; Smith et al. , 1985; Ayers et al. , 1990; Smith, 1991 ). The stratigraphic and temporal significance of erosional contacts near the Cretaceous/Tertiary boundary has been controversial, especially in the southeastern San Juan Basin near the Nacimiento uplift (Fig. I). Arguments for single or multiple unconformities at and near the KIT boundary (Baltz, 1967; Fassett and Hinds, 1971; Sikkink, 1987) have been countered by a hypothesis of nearly continuous sedimentation across the contact (Klute, 1986). Here, I present data that show the stratigraphic posit ions of regional unconformities in the Upper Cretaceous through Lower Eocene section and present a model that describes sedimentation adjacent to the episodically active Nacimicnto uplift. A complete treatment of stratigraphic problems involving the Fruitland, Kirtland and Ojo Alamo formations is beyond the scope of this report. STRATIGRAPHY The stratigraphic sequence of interest includes the Fruitland Formation, Kirtland Shale, Ojo Alamo Sandstone , Nacimiento Formation and San Jose Formation (F
圣胡安盆地上白垩统和古近系陆相地层记录了laramides时代抬升对白垩统前陆盆地的局部破坏和分割。不整合面在地层剖面(包括Fruitland组、Kirtland页岩和Ojo Alamo砂岩)中的重要性，以及白垩纪/第三纪边界的性质一直存在争议，特别是在靠近Nacimiento隆起的圣胡安盆地东南部。地表和地下测绘最近在Fruitland/ Kirtland和Ojo Alamo地层之间发现了一个不整合的富含沙子的流感小瓶单元，这里称为“单元B”，这可能解释了一些早期的测绘问题。梅萨波塔莱斯的B单元包含独特的河道砂岩和互层粉砂岩和泥岩，显示出斑驳和氧化剖面，是排水良好的洪泛平原的高能河流系统的典型特征。古流测量清楚地表明，“B单元”的大部分沉积与北至南的古斜坡有关。碎屑岩性表明，“B单元”砂岩与Ojo Alamo砂岩的基岩岩性相似。与Nacimiento向上隆起平行的由北向南的河道形成了“B单元”、Ojo Alamo砂岩、Nacimiento上部地层和圣何塞地层的古巴台萨段。平行于Nacimiento隆起并与之相邻的河道位置的保持，表明该地区在晚白垩世至早始新世期间持续存在同构造沉积。圣胡安盆地上白垩统和古近系陆相地层是在落基山脉南部白垩统海道撤退和Laramide(晚白垩统-始新统)隆升后的东北三角洲进积过程中沉积的(Baltz, 1967;Fassett and Hinds, 1971;Smith et al.， 1985;Ayers等人，1990;史密斯，1991)。白垩纪/第三纪边界附近侵蚀接触的地层学和时间意义一直存在争议，特别是在靠近Nacimiento隆起的圣胡安盆地东南部(图1)。在KIT边界及其附近存在单一或多个不整合的争论(Baltz, 1967;Fassett and Hinds, 1971;Sikkink, 1987)已经被几乎连续沉积的假说所反驳(Klute, 1986)。在这里，我提供的数据显示了上白垩纪到下始新世剖面的区域不整合的地层位置，并提出了一个模型，该模型描述了与偶然活动的naciminto隆起相邻的沉积。对涉及Fruitland、Kirtland和Ojo Alamo地层的地层问题的完整论述超出了本报告的范围。感兴趣的层序包括Fruitland组、Kirtland页岩、Ojo Alamo砂岩、Nacimiento组和San Jose组(图1)。1)果地组和科特兰页岩均由细粒至中粒砂岩和页岩组成(见Hunt等人，本指南)。这些单元的典型特征是只在地层较低的果地组中发现煤(Fassett和Hinds, 1971，第19页)。在最后一层煤之上的区域性相关薄页岩是挑选地下接触的有用标志(Ayers et al.， 1990)。无论使用哪一种定义，从其类型区域到圣胡安盆地东南部的Fruitland组和Kirtland页岩的地下对比表明，Kirtland页岩因侵蚀而被移除，而Fruitland组被截断在T2 IN, R5-7W的东南偏东，大约在Mesa Portales露头以东40-48公里(24-30英里)处(Fassett和Hinds, 1971;Ayers et al.， 1990)。Baltz(1967)在圣胡安盆地东南部的Fruitland和Kirtland(未划分)区分了非正式单元“A”和“B”，其依据是地层较高的“单元B”中砂岩的百分比更高，粒度更粗(图2)。“单元A”由粉质页岩、碳质页岩、煤和一些局部含有海洋化石的细粒砂岩组成。“单元B”的特点是基底，非常粗糙，细粒，交错层状砂岩，局部包含大块的硅化木材。“单元B”的多个粗粒透镜状砂岩被灰绿色、红色和局部紫色的泥岩、粉砂岩和膨润土灰色粘土隔开。Baltz(1967)表明，“B单元”侵蚀性地覆盖在较低的Fruitland上，并在“B单元”覆盖在picture Cliffs砂岩上的地方将其切割。Fassett和Hinds(1971)在圣胡安盆地东南部进行了区分，但他们没有绘制或显示“砂岩层在岩性上似乎与整个盆地的Fruitland砂岩层不同”的相关性(第17页)。 这些砂岩位于与“B单元”对应的地层中，被推断为与Fruitland组和Kirtland页岩同期沉积，以及后Fruitland沉积在ojo - Alamo砂岩不整合下部的河道中(第19页)。Mesa Portales的“B单元”部分相当于Klute的“上Kirtland页岩砂岩相”(1986年)。圣胡安盆地东南部Fru itland组与Ojo Alamo砂岩上部接触的位置及其整合或不整合性质一直存在争议(见Kl ute, 1986和Fassett et al.， 1987的讨论)。Mesa Portales地区“B单元”的一系列中粗粒砂岩和互层泥岩被一层厚砂岩覆盖，这种砂岩通常被称为Ojo Alamo砂岩，尽管并非所有的工人都认为它是该地层的基底砂岩(图2)。粗粒砂岩体被解释为与Fru itland格式上的Ojo Alamo砂岩的砂质和页岩的不整合接触(Fassett和Hinds, 1971;Fassett et al.， 1987)。Klute(1986)基于Mesa Portales上粗粒砂岩的岩性相似性和砂岩与页岩间的明显衔接，得出“Kirtland页岩”与Ojo Alamo砂岩接触面整合的结论。她没有讨论科特兰页岩区域截断的证据。我建议“B单元”的地层可以被认为是一个独立的地层单元，在Nacimiento隆起附近包含一个或多个不整合面(图2)。2).下面将详细讨论被称为“单元B”的序列中砂色调的意义。古新世Nacimiento组泥岩和细粒至粗粒砂岩整合覆盖在Ojo Alamo砂岩上。
{"title":"Upper Cretaceous and Paleogene stratigraphy and sedimentation adjacent to the Nacimiento uplift, southeastern San Juan Basin","authors":"L. Smith","doi":"10.56577/ffc-43.251","DOIUrl":"https://doi.org/10.56577/ffc-43.251","url":null,"abstract":"Uppermost Cretaceous and Paleogene terrestrial strata in the San Juan Basin record the local disruption and partitioning of the Cretaceous foreland basin by Laramide-aged up lifts. The importance of unconformities within the stratigraphic section, wh ich includes the Fruitland Formation, Kirtland Shale and Ojo Alamo Sandstone, and the nature of the Cretaceous/Tertiary boundary has been controversial, especially in the southeastern San Juan Basin near the Nacimiento uplift . Surface and subsurface mapping has recent ly identified an unconformity-bound sand-rich flu vial unit, here referred to as \"unit B,\" between the Fruitland/ Kirtland and Ojo Alamo formations, which may explain some of the earlier mapping problems . \" Unit B\" on Mesa Portales contains distinct channel sandstones and interbedded siltstones and mudrocks that show mottling and oxidation profiles typ ical of a high energy fluvial system with well-drained floodplains. Paleocurrent measurements clearly show that deposition of much of \"unit B\" was related to north-to-south paleoslopes. Detrital lithologies indicate that sandstones of \"unit B\" and the Ojo Alamo Sandstone were derived from similar bedrock lithologies . North-to-south directed channels, parallel to the Nacimiento up lift, were responsible for depositing \"unit B, \" the Ojo Alamo Sandstone, the upper Nacimiento Formation and the Cuba Mesa Member of the San Jose Formation . Maintenance of the position of channels parall el and adjacent to the Nacimiento uplift represents continued syntectonic sedimentation in this region from the Late Cretaceous through the early Eocene . INTRODUCTION Uppermost Cretaceous and Paleogene terrestrial strata in the San Juan Basin were deposited during northeast deltaic progradation following withdrawal of the Cretaceous seaway and subsequent Laramide (Late Cretaceous-Eocene) uplift within the southern Rocky Mountains (Baltz, 1967; Fassett and Hinds, 1971; Smith et al. , 1985; Ayers et al. , 1990; Smith, 1991 ). The stratigraphic and temporal significance of erosional contacts near the Cretaceous/Tertiary boundary has been controversial, especially in the southeastern San Juan Basin near the Nacimiento uplift (Fig. I). Arguments for single or multiple unconformities at and near the KIT boundary (Baltz, 1967; Fassett and Hinds, 1971; Sikkink, 1987) have been countered by a hypothesis of nearly continuous sedimentation across the contact (Klute, 1986). Here, I present data that show the stratigraphic posit ions of regional unconformities in the Upper Cretaceous through Lower Eocene section and present a model that describes sedimentation adjacent to the episodically active Nacimicnto uplift. A complete treatment of stratigraphic problems involving the Fruitland, Kirtland and Ojo Alamo formations is beyond the scope of this report. STRATIGRAPHY The stratigraphic sequence of interest includes the Fruitland Formation, Kirtland Shale, Ojo Alamo Sandstone , Nacimiento Formation and San Jose Formation (F","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129005116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
-The La Yentana Tongue of the Cliff House Sandstone has been the subject of several studies in the northwest and central San Juan Basin, in particular for oil and gas potential. The lack of drill-hole dala in the southeastern San Juan Basin had restricted detailed studies in this area to outcrops and a few oil and gas test logs. Logs from the New Mexico Bureau of Mines and Mineral Resources coal-quality drilling program ( 1985-1988), additional oil and gas drilling completed since the late 1970s, together with the older data provide sufficient subsurface data for detailed interpretations of stratigraphic relationships in the southeastern San Juan Basin. A 27-km cross section based on 24 geophysical logs was constructed north-northeastward from the outcrop area, 8 km east of Torreon Trading Post. The cross section transects the upper coal member of the Menefee, the La Ventana Tongue and the Lewis Shale. The maximum development of the La Ventana Tongue is clearly seen on the cross section, as is the relationship of the La Ventana to the coals within the upper coal member sequence. After a sudden landward shift of the shoreline that terminated the La Ventana buildup, a secondary stacking of barrier beach sandstones developed further inland. This unit is informally referred to in this report as the Chacra Mesa tongue. The intertonguing between the upper coal member of the Menefee and the La Ventana Tongue can be related to the principle of stratidynamics. This concept assumes continuing subsidence in a depositional environment and deals with transitional units. such as the upper coal member and the La Yentana, between the nonmarine and marine. The variables introduced are rate of subsidence and rate of shoreline shift. The La Ventana-upper coal member sequence developed during a time of minimal shoreline movement, with minor oscillations and variable sediment
{"title":"Interrelationships between the upper coal member of the Menefee Formation, the La Ventana Tongue, and the Lewis Shale in the southeastern San Juan Basin","authors":"E. C. Beaumont, Gretchen K. Hoffman","doi":"10.56577/ffc-43.207","DOIUrl":"https://doi.org/10.56577/ffc-43.207","url":null,"abstract":"-The La Yentana Tongue of the Cliff House Sandstone has been the subject of several studies in the northwest and central San Juan Basin, in particular for oil and gas potential. The lack of drill-hole dala in the southeastern San Juan Basin had restricted detailed studies in this area to outcrops and a few oil and gas test logs. Logs from the New Mexico Bureau of Mines and Mineral Resources coal-quality drilling program ( 1985-1988), additional oil and gas drilling completed since the late 1970s, together with the older data provide sufficient subsurface data for detailed interpretations of stratigraphic relationships in the southeastern San Juan Basin. A 27-km cross section based on 24 geophysical logs was constructed north-northeastward from the outcrop area, 8 km east of Torreon Trading Post. The cross section transects the upper coal member of the Menefee, the La Ventana Tongue and the Lewis Shale. The maximum development of the La Ventana Tongue is clearly seen on the cross section, as is the relationship of the La Ventana to the coals within the upper coal member sequence. After a sudden landward shift of the shoreline that terminated the La Ventana buildup, a secondary stacking of barrier beach sandstones developed further inland. This unit is informally referred to in this report as the Chacra Mesa tongue. The intertonguing between the upper coal member of the Menefee and the La Ventana Tongue can be related to the principle of stratidynamics. This concept assumes continuing subsidence in a depositional environment and deals with transitional units. such as the upper coal member and the La Yentana, between the nonmarine and marine. The variables introduced are rate of subsidence and rate of shoreline shift. The La Ventana-upper coal member sequence developed during a time of minimal shoreline movement, with minor oscillations and variable sediment","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133210382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Although the first report of uranium in New Mexico was from volcanic rocks in the Jemez Mountains, very litt le urani um has been produced ( < 20 ,000 lbs of U,0 , ) from the eastern San Juan Basin. Uranium occurs in Morri son Formation sandstones. other sandstones, the Todilto Formation, other sedimentary rocks. epithermal ve ins, and disseminated deposits in igneous and metamorphic rocks. Uranium deposits in the Morrison and Todilto Formations were deposited duri ng the Jurassic, although Tertiary-Quaternary oxidation and remobilization of some deposits may have occurred . Deposits in the Precambrian rocks in the Tusas Mountains are magmatic and related to grani tic and pegmatit ic rocks. Other uranium deposits in the eastern San Juan Basin may have been derived from devitriticat ion and leaching from the Bandelicr Tuff. The potential for nearfutu re development of uranium deposits in th is area is nil because of lack of demand, low uranium prices and low grade . 34 1
{"title":"Uranium deposits in the eastern San Juan Basin, Cibola, Sandoval and Rio Arriba Counties, New Mexico","authors":"V. McLemore, W. L. Chenoweth","doi":"10.56577/ffc-43.341","DOIUrl":"https://doi.org/10.56577/ffc-43.341","url":null,"abstract":"Although the first report of uranium in New Mexico was from volcanic rocks in the Jemez Mountains, very litt le urani um has been produced ( < 20 ,000 lbs of U,0 , ) from the eastern San Juan Basin. Uranium occurs in Morri son Formation sandstones. other sandstones, the Todilto Formation, other sedimentary rocks. epithermal ve ins, and disseminated deposits in igneous and metamorphic rocks. Uranium deposits in the Morrison and Todilto Formations were deposited duri ng the Jurassic, although Tertiary-Quaternary oxidation and remobilization of some deposits may have occurred . Deposits in the Precambrian rocks in the Tusas Mountains are magmatic and related to grani tic and pegmatit ic rocks. Other uranium deposits in the eastern San Juan Basin may have been derived from devitriticat ion and leaching from the Bandelicr Tuff. The potential for nearfutu re development of uranium deposits in th is area is nil because of lack of demand, low uranium prices and low grade . 34 1","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129724542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Supplemental road log 2: From Cuba to Nacimiento Copper mine","authors":"S. Lucas, T. Williamson","doi":"10.56577/ffc-43.71","DOIUrl":"https://doi.org/10.56577/ffc-43.71","url":null,"abstract":"","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"185 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123147230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Charles H. Sternberg and the collection of late Cretaceous vertebrate fossils from the San Juan Basin, New Mexico","authors":"A. Hunt, S. Lucas, N. Mateer","doi":"10.56577/ffc-43.241","DOIUrl":"https://doi.org/10.56577/ffc-43.241","url":null,"abstract":"","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"511 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116539152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
- Fossil 111ammals fro111 the San Jose For111ation in the San Juan Basin are the only 111cans by which an age can be assigned to the San Jose Formation. These mam111als indicate an early Eocene (middle Wasatchian, Lysitean) age for the entire San Jose Formation except its basal strata, which have not produced age-diagnostic fossils. Selected, age-diagnostic fossil 111am111als from the San Jose Formation are illustrated here.
{"title":"Fossil mammals and the early Eocene age of the San Jose Formation, San Juan Basin, New Mexico","authors":"S. Lucas, T. Williamson","doi":"10.56577/ffc-43.311","DOIUrl":"https://doi.org/10.56577/ffc-43.311","url":null,"abstract":"- Fossil 111ammals fro111 the San Jose For111ation in the San Juan Basin are the only 111cans by which an age can be assigned to the San Jose Formation. These mam111als indicate an early Eocene (middle Wasatchian, Lysitean) age for the entire San Jose Formation except its basal strata, which have not produced age-diagnostic fossils. Selected, age-diagnostic fossil 111am111als from the San Jose Formation are illustrated here.","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115601285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Woodward, Michael C. Hultgren, David L. Crouse, Margaret A. Merrick
The Nacimiento-Gallina fault system trends nonherly for about 110 km. separating the San Juan Basin and the Colorado Plateau from the Rocky Mountain foreland to the east. From south to north the Pajarito, Nacimiento, Gallina and Tierra Montafiosa faults comprise this system. The east-dipping Pajarito and Nacimiento fau lts bound the west side of the Nacimiento uplift and are characterized mainly by reverse separation. The Gallina and Tierra Montafiosa faults are nearly vertical and define the west boundary of the Gallina-Archuleta arch . Movement on the Gallina fault had both dip-slip and strike-slip components and displacement on the Montafiosa fault was essentially dip slip. This complicated eastern boundary of the Colorado Plateau has led to markedly different interpretations of its tectonic evolution. mainly because of previous lack of detailed geologic maps. Since the pioneering work of Vincent Kelley in the 1950s there has been general agreement that the Colorado Plateau underwent right shift with respect to the adjacent Rocky Mountain foreland in northern New Mexico prior to the Pajarito and Nacimiento faults rupturing the sedimentary cover. However, there has been considerable debate concerning the amount of right slip (as distinct from shift) along the NacimientoGallina fault system. Right shift in Precambrian basement rocks among the eastern margin of the Colorado Plateau in late Paleocene to mid-Eocene time created northwest-trending echelon fo lds in the overlying Phanerozoic strata. This was followed by development of a west-facing monocline that was cut by the Pajarito and Nacimiento reverse faults. As the San Juan Basin subsided it was differentially folded relative to the GallinaArchuleta arch. resulting in a component of strike slip along the Gallina fault. This differential folding resu lted in variable offset along the Gallina fault with nonmatching folds on opposite sides of the fault. The axes of the folds do not predate fault movement and therefore cannot be used to determine the amount of strike slip. Lack of piercing points along the Pajarito . Nacimiento and Gallina faults precludes precise calculations of the strike-slip component of movement. These discontinuous faults with relative ly short traces suggest that only minor amounts of right slip occurred along them. Thus, right shift of the Colorado Plateau dies out at the north end of the Gallina fault and displacement on the Tierra Montafiosa fault is principally dip slip. 103
{"title":"Geometry of Nacimiento-Gallina fault system, northern New Mexico","authors":"L. Woodward, Michael C. Hultgren, David L. Crouse, Margaret A. Merrick","doi":"10.56577/ffc-43.103","DOIUrl":"https://doi.org/10.56577/ffc-43.103","url":null,"abstract":"The Nacimiento-Gallina fault system trends nonherly for about 110 km. separating the San Juan Basin and the Colorado Plateau from the Rocky Mountain foreland to the east. From south to north the Pajarito, Nacimiento, Gallina and Tierra Montafiosa faults comprise this system. The east-dipping Pajarito and Nacimiento fau lts bound the west side of the Nacimiento uplift and are characterized mainly by reverse separation. The Gallina and Tierra Montafiosa faults are nearly vertical and define the west boundary of the Gallina-Archuleta arch . Movement on the Gallina fault had both dip-slip and strike-slip components and displacement on the Montafiosa fault was essentially dip slip. This complicated eastern boundary of the Colorado Plateau has led to markedly different interpretations of its tectonic evolution. mainly because of previous lack of detailed geologic maps. Since the pioneering work of Vincent Kelley in the 1950s there has been general agreement that the Colorado Plateau underwent right shift with respect to the adjacent Rocky Mountain foreland in northern New Mexico prior to the Pajarito and Nacimiento faults rupturing the sedimentary cover. However, there has been considerable debate concerning the amount of right slip (as distinct from shift) along the NacimientoGallina fault system. Right shift in Precambrian basement rocks among the eastern margin of the Colorado Plateau in late Paleocene to mid-Eocene time created northwest-trending echelon fo lds in the overlying Phanerozoic strata. This was followed by development of a west-facing monocline that was cut by the Pajarito and Nacimiento reverse faults. As the San Juan Basin subsided it was differentially folded relative to the GallinaArchuleta arch. resulting in a component of strike slip along the Gallina fault. This differential folding resu lted in variable offset along the Gallina fault with nonmatching folds on opposite sides of the fault. The axes of the folds do not predate fault movement and therefore cannot be used to determine the amount of strike slip. Lack of piercing points along the Pajarito . Nacimiento and Gallina faults precludes precise calculations of the strike-slip component of movement. These discontinuous faults with relative ly short traces suggest that only minor amounts of right slip occurred along them. Thus, right shift of the Colorado Plateau dies out at the north end of the Gallina fault and displacement on the Tierra Montafiosa fault is principally dip slip. 103","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128528091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Wright-Dunbar, R. Zech, G. Crandall, D. Katzman
{"title":"Strandplain and deltaic depositional models for the Point Lookout Sandstone, San Juan Basin and Four Corners Platform, New Mexico and Colorado","authors":"R. Wright-Dunbar, R. Zech, G. Crandall, D. Katzman","doi":"10.56577/ffc-43.199","DOIUrl":"https://doi.org/10.56577/ffc-43.199","url":null,"abstract":"","PeriodicalId":325871,"journal":{"name":"San Juan Basin IV","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126857650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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