This investigation uses optically stimulated luminescence (OSL) dating to examine the chronology of colluvial apron development and to help constrain long-term process rates within the mesa and canyon systems of the Pajarito Plateau in north-central New Mexico. In addition to ages, the OSL data provide insight into the dynamic interactions of surface processes within the mesa and canyon systems. Our results can be interpreted to suggest that foot-slope deposits within Canada del Buey represent a complex interplay of depositional processes in which eolian inputs from outside of the Pajarito Plateau play a role. Depositional ages, both on the mesa top and in foot slopes, record episodic inputs to the system in the late Pleistocene, middle Holocene, and late Holocene. These periods correlate well to eolian activity and significant climatic events in the Southern Plains and desert Southwest.
{"title":"Chronology of colluvial apron deposition within Canada del Buey, Pajarito Plateau, New Mexico","authors":"K. Lepper, K. Crowell, C. Wilson","doi":"10.58799/nmg-v33n1.3","DOIUrl":"https://doi.org/10.58799/nmg-v33n1.3","url":null,"abstract":"This investigation uses optically stimulated luminescence (OSL) dating to examine the chronology of colluvial apron development and to help constrain long-term process rates within the mesa and canyon systems of the Pajarito Plateau in north-central New Mexico. In addition to ages, the OSL data provide insight into the dynamic interactions of surface processes within the mesa and canyon systems. Our results can be interpreted to suggest that foot-slope deposits within Canada del Buey represent a complex interplay of depositional processes in which eolian inputs from outside of the Pajarito Plateau play a role. Depositional ages, both on the mesa top and in foot slopes, record episodic inputs to the system in the late Pleistocene, middle Holocene, and late Holocene. These periods correlate well to eolian activity and significant climatic events in the Southern Plains and desert Southwest.","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174580","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}
Cameleolopha bellaplicata (Shumard 1860) is an easily recognized fossil oyster that occurs abundantly in sandy strata in Arizona, Colorado, New Mexico, Utah, and Texas, where it is restricted to the middle Turonian ammonite zones of Prionocyclus hyatti and P. macombi. It is a distinctive, medium-sized, plano-convex, ribbed oyster that has an undulating or zigzag margin and a small to nonexistent attachment scar; it occurs in great numbers, usually as original shells. In central New Mexico, C. bellaplicata is an excellent guide fossil to the Fite Ranch Sandstone Member of the Tres Hermanos Formation, which was deposited as nearshore sands during the second major transgression of the Late Cretaceous seaway in the state. Since 1965 Cameleolopha bellaplicata has been split, erroneously, into two chronological subspecies: a supposedly older, more coarsely ribbed form, C. bellaplicata novamexicana (Kauffman), that was thought to be restricted to the middle part of the Prionocyclus hyatti Zone, and a younger, more delicately sculptured form, C. bellaplicata bellaplicata (Shumard), that ranges into the overlying P. macombi Zone. Although the two subspecies have type localities in Socorro County, New Mexico, and Grayson County, Texas, respectively, their supposed chronostratigraphic relationship could not be established at either type locality because the two supposed subspecies do not occur together at either type locality. Presumably, this chronostratigraphic relationship was established in Huerfano County, Colorado, where the ranges of the two morphotypes were interpreted to lie one above the other within the P. hyatti Zone and with no zone of overlap. However, the chronological separation of the morphotypes by ammonite zone was based on a misidentification of the prionocyclid ammonite that occurs with the holotype of Cameleolopha bellaplicata novamexicana. Initially, only fragments of large individual prionocyclids were found; they were identified as Prionocyclus hyatti. Recent collections of ammonites from the type area of C. b. novamexicana contain small diameter internal molds that are unequivocally the younger P. macombi, rather than the older P. hyatti; associated fauna includes Inoceramus dimidius White, which substantiates assignment of the holotype of C. b. novamexicana to the younger P. macombi Zone. With the index ammonite identified correctly, there is no chronostratigraphic basis for the subspecies separation. A reinterpretation of the original morphometric data shows that the presumed differences between the subspecies are subtle and represent normal species variation. Beginning in the late 1940s, strata that are now included in the Tres Hermanos Formation in New Mexico and Arizona were correlated with and included in the stratigraphically higher Gallup Sandstone. In the late 1970s, collections of Cameleolopha bellaplicata and its descendant C. lugubris from the Zuni and Acoma Basins in west and west-central New Mexico were instrumental i
{"title":"The Late Cretaceous oyster Cameleolopha bellaplicata (Shumard 1860), guide fossil to middle Turonian strata in New Mexico","authors":"S. Hook, W. A. Cobban","doi":"10.58799/nmg-v33n3.67","DOIUrl":"https://doi.org/10.58799/nmg-v33n3.67","url":null,"abstract":"Cameleolopha bellaplicata (Shumard 1860) is an easily recognized fossil oyster that occurs abundantly in sandy strata in Arizona, Colorado, New Mexico, Utah, and Texas, where it is restricted to the middle Turonian ammonite zones of Prionocyclus hyatti and P. macombi. It is a distinctive, medium-sized, plano-convex, ribbed oyster that has an undulating or zigzag margin and a small to nonexistent attachment scar; it occurs in great numbers, usually as original shells. In central New Mexico, C. bellaplicata is an excellent guide fossil to the Fite Ranch Sandstone Member of the Tres Hermanos Formation, which was deposited as nearshore sands during the second major transgression of the Late Cretaceous seaway in the state. Since 1965 Cameleolopha bellaplicata has been split, erroneously, into two chronological subspecies: a supposedly older, more coarsely ribbed form, C. bellaplicata novamexicana (Kauffman), that was thought to be restricted to the middle part of the Prionocyclus hyatti Zone, and a younger, more delicately sculptured form, C. bellaplicata bellaplicata (Shumard), that ranges into the overlying P. macombi Zone. Although the two subspecies have type localities in Socorro County, New Mexico, and Grayson County, Texas, respectively, their supposed chronostratigraphic relationship could not be established at either type locality because the two supposed subspecies do not occur together at either type locality. Presumably, this chronostratigraphic relationship was established in Huerfano County, Colorado, where the ranges of the two morphotypes were interpreted to lie one above the other within the P. hyatti Zone and with no zone of overlap. However, the chronological separation of the morphotypes by ammonite zone was based on a misidentification of the prionocyclid ammonite that occurs with the holotype of Cameleolopha bellaplicata novamexicana. Initially, only fragments of large individual prionocyclids were found; they were identified as Prionocyclus hyatti. Recent collections of ammonites from the type area of C. b. novamexicana contain small diameter internal molds that are unequivocally the younger P. macombi, rather than the older P. hyatti; associated fauna includes Inoceramus dimidius White, which substantiates assignment of the holotype of C. b. novamexicana to the younger P. macombi Zone. With the index ammonite identified correctly, there is no chronostratigraphic basis for the subspecies separation. A reinterpretation of the original morphometric data shows that the presumed differences between the subspecies are subtle and represent normal species variation. Beginning in the late 1940s, strata that are now included in the Tres Hermanos Formation in New Mexico and Arizona were correlated with and included in the stratigraphically higher Gallup Sandstone. In the late 1970s, collections of Cameleolopha bellaplicata and its descendant C. lugubris from the Zuni and Acoma Basins in west and west-central New Mexico were instrumental i","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71175107","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":"A rare, large artesian subaqueous spring in the upper Rio Grande","authors":"P. Bauer, P. Johnson","doi":"10.58799/nmg-v32n1.26","DOIUrl":"https://doi.org/10.58799/nmg-v32n1.26","url":null,"abstract":"","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174705","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}
As highlighted in this issue’s Gallery of Geology on page 24, large, severe wildfires have become part of the New Mexico late spring and early summer experience in the last few decades. Such fires have considerable relevance to geomorphologists, as erosion rates in mountainous landscapes are often dramatically increased in the several years after severe fires. Erosion and sediment transport often take place during major debris flows and flash floods (Fig. 1). These events are most commonly triggered by intense thunderstorm rainfall, as in New Mexico’s summer monsoon, and very rapid runoff from slopes devoid of vegetation or forest litter. Although water-repellent soils formed by fire effects are often cited as the primary cause of increased runoff, the creation of extensive bare, smooth soil surfaces alone is more than sufficient— for example, consider the erosion that would occur on a plowed, smooth farm field at slope angles of 15–30° or more! The extreme flows that are generated can entrain huge volumes of sediment as they course down slopes and channels. Events of this nature affected a number of small, steep drainages in the Sacramento Mountains southeast of Cloudcroft after the 2002 Penasco fire. Large quantities of mudto boulder-sized sediment may be deposited on alluvial fans along the valley margins, and in some cases deep gullies are also cut in the fans. Major damage to roads, buildings, and property resulted in several locations in the Penasco fire area, as valleyside alluvial fans are common sites for residential and other development. Along with their importance in understanding geologic hazards and watershed impacts, sediments deposited on alluvial fans by postfire debris flows and floods also provide a means of assessing the timing and spatial distribution of past forest fires, and relations between fire and climate, in particular episodes of severe drought. These sediments are often rich in charcoal fragments from the burned area, which allows radiocarbon dating of fire-related sedimentation events thousands of years into the past, providing an important supplement to the more commonly available tree-ring fire histories. Tree-ring dating has provided a wealth of information on low-severity surface fires that scar trees, but leave them living. Such fires swept through the understory of many southwestern forests every few years to a few decades before European settlement and intensified grazing, logging, and fire suppression in the late 1800s (e.g., Brown et al. 2001). However, tree-ring fire-scar records extend back about 500 yrs at most, and do not provide data on severe fires that kill large stands of trees. Standdestroying fires can be dated via the ages of living trees that germinated after fire, but this reveals the last such fire only, and again is limited to about the last 500 yrs. Therefore, alluvial sediments can greatly extend fire histories, albeit with greater uncertainty in ages. Climatic change on time scales of a th
正如本期《地质画廊》第24页所强调的那样，在过去的几十年里，大规模、严重的野火已经成为新墨西哥州春末夏初经历的一部分。这种火灾与地貌学有相当大的关系，因为在严重火灾发生后的几年中，山区景观的侵蚀率通常会急剧增加。侵蚀和沉积物迁移通常发生在主要的泥石流和山洪暴发期间(图1)。这些事件最常见的触发因素是强雷暴降雨，如新墨西哥州的夏季季风，以及从没有植被或森林凋落物的斜坡上快速径流。虽然由火灾效应形成的拒水土壤通常被认为是径流增加的主要原因，但仅产生广泛的光秃秃的光滑土壤表面就足够了——例如，考虑在坡度为15-30°或更大的犁过的光滑农田上发生的侵蚀!由此产生的极端水流会带着大量的沉积物沿着斜坡和河道流下。2002年佩纳斯科大火后，这种性质的事件影响了克劳德克罗夫特东南部萨克拉门托山脉的一些小而陡峭的排水系统。大量泥砾大小的沉积物可能沉积在沿山谷边缘的冲积扇上，在某些情况下，冲积扇也会切割出深沟。由于山谷冲积扇是住宅和其他开发的常见地点，佩纳斯科火灾区域的几个地点对道路、建筑物和财产造成了重大破坏。除了对了解地质灾害和流域影响的重要性外，火灾后泥石流和洪水沉积在冲积扇上的沉积物还提供了评估过去森林火灾的时间和空间分布以及火灾与气候(特别是严重干旱事件)之间关系的手段。这些沉积物通常富含来自烧毁地区的木炭碎片，这使得放射性碳定年法可以确定数千年前与火灾有关的沉积事件，为更常见的树木年轮火灾历史提供重要补充。树木年轮测年提供了大量关于低强度地表火灾的信息，这些火灾会损伤树木，但会使它们存活下来。在19世纪后期欧洲人定居并加强放牧、伐木和灭火之前，这种火灾每隔几年到几十年就会席卷许多西南森林的林下植被(例如，Brown et al. 2001)。然而，树木年轮的火痕记录最多可以追溯到500年前，并没有提供导致大片树木死亡的严重火灾的数据。标准的破坏性火灾可以通过火灾后发芽的活树的年龄来确定，但这只揭示了最后一次这样的火灾，而且也仅限于最近的500年左右。因此，冲积沉积物可以极大地延长火灾历史，尽管年龄的不确定性更大。一千年或更长的时间尺度上的气候变化对全新世(自最后一次大陆冰期以来的约12000年)的地球环境产生了强烈影响。因此，在这样的时间尺度上，火灾活动对气候变化的敏感性是非常有趣的。这对于理解未来干旱对新墨西哥州山林的潜在影响也至关重要，因为预测下个世纪的变暖在树木年轮火灾年表覆盖的短时间尺度上是没有先例的。
{"title":"The Holocene record of fire and erosion in the southern Sacramento Mountains and its relation to climate","authors":"G. Meyer, J. Frechette","doi":"10.58799/nmg-v32n1.19","DOIUrl":"https://doi.org/10.58799/nmg-v32n1.19","url":null,"abstract":"As highlighted in this issue’s Gallery of Geology on page 24, large, severe wildfires have become part of the New Mexico late spring and early summer experience in the last few decades. Such fires have considerable relevance to geomorphologists, as erosion rates in mountainous landscapes are often dramatically increased in the several years after severe fires. Erosion and sediment transport often take place during major debris flows and flash floods (Fig. 1). These events are most commonly triggered by intense thunderstorm rainfall, as in New Mexico’s summer monsoon, and very rapid runoff from slopes devoid of vegetation or forest litter. Although water-repellent soils formed by fire effects are often cited as the primary cause of increased runoff, the creation of extensive bare, smooth soil surfaces alone is more than sufficient— for example, consider the erosion that would occur on a plowed, smooth farm field at slope angles of 15–30° or more! The extreme flows that are generated can entrain huge volumes of sediment as they course down slopes and channels. Events of this nature affected a number of small, steep drainages in the Sacramento Mountains southeast of Cloudcroft after the 2002 Penasco fire. Large quantities of mudto boulder-sized sediment may be deposited on alluvial fans along the valley margins, and in some cases deep gullies are also cut in the fans. Major damage to roads, buildings, and property resulted in several locations in the Penasco fire area, as valleyside alluvial fans are common sites for residential and other development. Along with their importance in understanding geologic hazards and watershed impacts, sediments deposited on alluvial fans by postfire debris flows and floods also provide a means of assessing the timing and spatial distribution of past forest fires, and relations between fire and climate, in particular episodes of severe drought. These sediments are often rich in charcoal fragments from the burned area, which allows radiocarbon dating of fire-related sedimentation events thousands of years into the past, providing an important supplement to the more commonly available tree-ring fire histories. Tree-ring dating has provided a wealth of information on low-severity surface fires that scar trees, but leave them living. Such fires swept through the understory of many southwestern forests every few years to a few decades before European settlement and intensified grazing, logging, and fire suppression in the late 1800s (e.g., Brown et al. 2001). However, tree-ring fire-scar records extend back about 500 yrs at most, and do not provide data on severe fires that kill large stands of trees. Standdestroying fires can be dated via the ages of living trees that germinated after fire, but this reveals the last such fire only, and again is limited to about the last 500 yrs. Therefore, alluvial sediments can greatly extend fire histories, albeit with greater uncertainty in ages. Climatic change on time scales of a th","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174894","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}
Cretaceous marine and nonmarine strata of late Albian–middle Cenomanian age are exposed around the Cerro de Cristo Rey uplift in southern Doña Ana County, New Mexico. These strata comprise a section approximately 350 m thick and are assigned to the (ascending order) Finlay, Del Norte, Smeltertown, Muleros, Mesilla Valley, Mojado (=“Anapra”), Del Rio, Buda, and Mancos (=“Boquillas”) Formations. Macrofossils and microfossils from these strata indicate that the Finlay, Del Norte, Smeltertown, Muleros, and Mesilla Valley Formations are of late Albian age, whereas the Del Rio, Buda, and Mancos Formations are of Cenomanian age. The base of the Cenomanian is most likely at a trangressive surface within the uppermost Mojado Formation. The late Albian (Manuaniceras powelli Zone) to early Cenomanian (Neophlycticeras hyatti Zone) sedimentary succession at Cerro de Cristo Rey consists of alternating fossiliferous limestone, shale with limestone and sandstone intercalations, and sandstone. Muddy limestone types are commonly wavy to nodular and represent deposits of an open-marine shelf environment below wave base. Intercalated coquina beds rich in mollusc shells are interpreted as storm layers. Shale was deposited in an open-shelf environment below or near wave base during periods of increased siliciclastic influx. Intercalated thin limestone and sandstone beds are inferred to be storm layers. The siliciclastic Mojado Formation is a regressive-transgressive succession formed in depositional environments ranging from lower shoreface to upper shoreface and even fluvial, again overlain by shallow-marine siliciclastics. Although the Washita Group section at Cerro de Cristo Rey is much thicker and displays some differences in facies, the succession shows similar transgressive and regressive trends compared to the Washita Group of north Texas. Thus, we recognize eight unconformity-bounded depositional cycles in the Cretaceous section at Cerro de Cristo Rey, the upper Finlay Formation (youngest cycle of the Fredericksburg Group), lower Mancos Formation (base of Greenhorn cycle), and six Washita Group cycles: WA1 = Del Norte Formation, WA2 = Smeltertown Formation, WA3 = Muleros Formation, WA4 = most of Mesilla Valley Formation, WA5 = uppermost Mesilla Valley Formation and most of Mojado Formation, and WA6 = uppermost Mojado and Del Rio and Buda Formations. The persistence of cycles from the tectonically passive, openmarine margin of the Gulf of Mexico into the tectonically active Chihuahua trough suggests that regional if not global eustasy, not local tectonism, drove late Early to early Late Cretaceous sedimentation at Cerro de Cristo Rey. Introduction Cerro de Cristo Rey is a prominent peak in Doña Ana County, New Mexico, just north of the U.S.–Mexican border and just west of the city of El Paso, Texas (Fig. 1). The mountain was long referred to as the Cerro de Muleros, but was renamed Cerro de Cristo Rey (“Sierra” de Cristo Rey of Hook 2008 and Cobban et al. 2008,
在新墨西哥州Doña Ana县南部的Cerro de Cristo Rey隆起周围，暴露出了白垩纪晚期-中Cenomanian时代的海相和非海相地层。这些地层包括一个约350米厚的剖面，依次为Finlay、Del Norte、Smeltertown、Muleros、Mesilla Valley、Mojado(=“Anapra”)、Del里约热内卢、Buda和Mancos(=“Boquillas”)地层。这些地层的宏观化石和微化石表明，Finlay组、Del Norte组、Smeltertown组、Muleros组和Mesilla Valley组属于晚Albian时代，而Del里约热内卢组、Buda组和Mancos组属于Cenomanian时代。Cenomanian的基底极有可能位于Mojado组最上层的一个海侵面。Cerro de Cristo Rey晚Albian (Manuaniceras powelli带)至早Cenomanian (neophlyticeras hyatti带)沉积序列由交替的化石灰岩、页岩(灰岩和砂岩夹层)和砂岩组成。泥质灰岩类型通常为波浪状或结节状，代表了波基下方的开放海洋陆架环境的沉积。含有丰富软体动物壳的嵌层鳕鱼床被解释为风暴层。页岩沉积在波基以下或波基附近的开放陆架环境中，形成于硅质内流增加的时期。夹层薄灰岩和砂岩层被推断为风暴层。莫哈多组是一个沉积环境由下滨面到上滨面甚至河流沉积的回退海侵序列，上覆浅海相硅质塑料。虽然Cerro de Cristo Rey的Washita组剖面较厚，且在相上存在一定差异，但其演替与德克萨斯州北部的Washita组表现出相似的海侵和退退趋势。因此，我们在Cerro de Cristo Rey白垩纪剖面中发现了8个不整合界沉积旋回，即上Finlay组(Fredericksburg群最年轻的旋回)、下Mancos组(Greenhorn群的基底)和6个Washita群旋回。WA1 = Del Norte组，WA2 = Smeltertown组，WA3 = Muleros组，WA4 = Mesilla Valley组大部分，WA5 = Mesilla Valley组上部和Mojado组大部分，WA6 = Mojado组上部和Del里约热内卢组和Buda组。从构造被动的墨西哥湾开放海缘到构造活跃的奇瓦瓦海槽的持续旋回表明，区域性的(如果不是全球性的)游动，而不是局部的构造作用，推动了早白垩世晚期至晚白垩世早期的Cerro de Cristo Rey沉积。介绍塞罗迪克里斯托。雷夫人安娜县是一个杰出的高峰,新墨西哥,美墨边境以北和埃尔帕索城西边,德州(图1)。这座山被称为塞罗迪米尔罗,但改名为塞罗迪克里斯托。雷(Sierra de克里斯托。雷钩2008和班et al ., 2008年也出现在美国地质调查局(U.S. Geological Survey)地区的地形图)认可的大型雕像基督在十字架上的波峰。这座山海拔1425米(4675英尺)(洛夫乔伊1976;钩2008)。Cerro de Cristo Rey的核心是一个安山岩岩纹岩，始新世的Muleros安山岩(图2)。断裂的白垩纪海相地层，局部受到安山岩侵入引发的重力滑动构造的强烈变形”(Lovejoy 1976，第24页)。白垩纪地层厚度约为350 m，包括早白垩世(晚阿尔比世)和晚白垩世(早-中Cenomanian)时期的岩石(图3-4)。这些岩石已经被研究了一个多世纪，最著名的是Böse(1910)和Strain(1976)。在这里，我们首次详细介绍了Cerro de Cristo Rey隆起新墨西哥周边白垩纪地层的岩石地层学和沉积岩石学。我们将这些数据与古生物学和区域相关性结合起来，首次详细解释了白垩纪剖面的沉积环境和旋回地层学。图1 - Cerro de Cristo Rey在Doña南部的位置，Ana县，新墨西哥州(洛夫乔伊1976年之后)。∆表示始新世火成岩侵入岩——Cerro de Cristo Rey、Cerro de la Mina、Campus安山岩、Three Sisters和Vado Hill。
{"title":"Cretaceous stratigraphy, paleontology, petrography. Depositional environments, and cycle stratigraphy at Cerro de Cristo Rey, Dona Ana County, New Mexico","authors":"S. Lucas, K. Krainer, J. Spielmann, K. Durney","doi":"10.58799/nmg-v32n4.103","DOIUrl":"https://doi.org/10.58799/nmg-v32n4.103","url":null,"abstract":"Cretaceous marine and nonmarine strata of late Albian–middle Cenomanian age are exposed around the Cerro de Cristo Rey uplift in southern Doña Ana County, New Mexico. These strata comprise a section approximately 350 m thick and are assigned to the (ascending order) Finlay, Del Norte, Smeltertown, Muleros, Mesilla Valley, Mojado (=“Anapra”), Del Rio, Buda, and Mancos (=“Boquillas”) Formations. Macrofossils and microfossils from these strata indicate that the Finlay, Del Norte, Smeltertown, Muleros, and Mesilla Valley Formations are of late Albian age, whereas the Del Rio, Buda, and Mancos Formations are of Cenomanian age. The base of the Cenomanian is most likely at a trangressive surface within the uppermost Mojado Formation. The late Albian (Manuaniceras powelli Zone) to early Cenomanian (Neophlycticeras hyatti Zone) sedimentary succession at Cerro de Cristo Rey consists of alternating fossiliferous limestone, shale with limestone and sandstone intercalations, and sandstone. Muddy limestone types are commonly wavy to nodular and represent deposits of an open-marine shelf environment below wave base. Intercalated coquina beds rich in mollusc shells are interpreted as storm layers. Shale was deposited in an open-shelf environment below or near wave base during periods of increased siliciclastic influx. Intercalated thin limestone and sandstone beds are inferred to be storm layers. The siliciclastic Mojado Formation is a regressive-transgressive succession formed in depositional environments ranging from lower shoreface to upper shoreface and even fluvial, again overlain by shallow-marine siliciclastics. Although the Washita Group section at Cerro de Cristo Rey is much thicker and displays some differences in facies, the succession shows similar transgressive and regressive trends compared to the Washita Group of north Texas. Thus, we recognize eight unconformity-bounded depositional cycles in the Cretaceous section at Cerro de Cristo Rey, the upper Finlay Formation (youngest cycle of the Fredericksburg Group), lower Mancos Formation (base of Greenhorn cycle), and six Washita Group cycles: WA1 = Del Norte Formation, WA2 = Smeltertown Formation, WA3 = Muleros Formation, WA4 = most of Mesilla Valley Formation, WA5 = uppermost Mesilla Valley Formation and most of Mojado Formation, and WA6 = uppermost Mojado and Del Rio and Buda Formations. The persistence of cycles from the tectonically passive, openmarine margin of the Gulf of Mexico into the tectonically active Chihuahua trough suggests that regional if not global eustasy, not local tectonism, drove late Early to early Late Cretaceous sedimentation at Cerro de Cristo Rey. Introduction Cerro de Cristo Rey is a prominent peak in Doña Ana County, New Mexico, just north of the U.S.–Mexican border and just west of the city of El Paso, Texas (Fig. 1). The mountain was long referred to as the Cerro de Muleros, but was renamed Cerro de Cristo Rey (“Sierra” de Cristo Rey of Hook 2008 and Cobban et al. 2008,","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174508","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}
As described in the accompanying Gallery of Geology article, springtime is wildfire season in the Southwest. The table of recent fires in New Mexico on page 25 is dominated by events in May and June. Hot, dry, windy conditions in the spring promote wildfire development. Drought conditions make some years more fire prone than others, and long-term climatic changes in temperature and precipitation affect the general fire regime in the Southwest (Meyer and Frechette, this issue). The onset of the North American monsoon, usually around the beginning of July, brings higher humidity and intermittent rainfall, dampening grass and dry fuel and generally marking the end of the fire season (and the acceleration of plant growth that provides fuel for the next year's fire season). It is also possible that wildfires affect the regional climate, although this connection is harder to quantify. Large fires inject large quantities of soot and smoke high into the atmosphere. Winds then blow these particulates across the Southwest, so the impact of locally injected particulates can spread far beyond the source. Other sources of particulates, such as widespread air pollution, have been shown to block sunlight and depress precipitation. A study of the South Asian monsoon showed that black carbon soot associated with air pollution decreases the radiative heating of the surface, thereby altering atmospheric stability and largescale temperature gradients that drive monsoon circulations (Ramanathan et al. 2005). Compared to the South Asian brown cloud, southwestern wildfires in most years generate much smaller quantities of particulates that remain airborne for a shorter period of time. However the timing of the southwestern fire season in late spring is potentially just right to affect the onset of the monsoon. The onset date is highly correlated with total seasonal precipitation, such that late onset is usually a precursor of low total summer rainfall (Higgins et al. 1997). We describe here a preliminary assessment of the hypothesis that large spring wildfires could depress monsoonal precipitation, by comparing a 25-yr time series of acreage burned in southwestern wildfires in June with the subsequent precipitation observed in July and August (Van Alst 2009). Data
正如《地质画廊》中所描述的那样，春天是西南地区的野火季节。在第25页的新墨西哥州最近的火灾列表中，5月和6月的火灾占据了主要位置。春天炎热、干燥、多风的环境促进了野火的发展。干旱条件使某些年份比其他年份更容易发生火灾，温度和降水的长期气候变化影响了西南地区的一般火灾状况(Meyer和Frechette，本期)。北美季风的开始，通常在7月初左右，带来更高的湿度和间歇性降雨，潮湿的草和干燥的燃料，通常标志着火灾季节的结束(以及植物生长的加速，为下一年的火灾季节提供燃料)。野火也有可能影响区域气候，尽管这种联系很难量化。大火将大量的煤烟和烟雾喷射到高空的大气中。然后，风把这些微粒吹过西南部，因此，局部注入的微粒的影响可以远远超出源头。其他颗粒来源，如广泛的空气污染，已被证明会阻挡阳光和减少降水。南亚季风的一项研究表明，与空气污染有关的黑碳烟减少了地表的辐射加热，从而改变了驱动季风环流的大气稳定性和大尺度温度梯度(Ramanathan et al. 2005)。与南亚的棕色云相比，西南地区的野火在大多数年份产生的颗粒数量要少得多，这些颗粒在空气中停留的时间更短。然而，晚春西南部火灾季节的时机可能正好影响季风的开始。开始日期与季节总降水量高度相关，因此开始晚通常是夏季总降雨量低的前兆(Higgins et al. 1997)。本文通过比较西南地区6月野火烧毁面积的25年时间序列与随后7月和8月观测到的降水，对春季野火可能抑制季风降水的假设进行了初步评估(Van Alst 2009)。数据
{"title":"Interannual variablity of wildfires and summer precipitation in the Southwest","authors":"D. Gutzler, Laura J. Van Alst","doi":"10.58799/nmg-v32n1.22","DOIUrl":"https://doi.org/10.58799/nmg-v32n1.22","url":null,"abstract":"As described in the accompanying Gallery of Geology article, springtime is wildfire season in the Southwest. The table of recent fires in New Mexico on page 25 is dominated by events in May and June. Hot, dry, windy conditions in the spring promote wildfire development. Drought conditions make some years more fire prone than others, and long-term climatic changes in temperature and precipitation affect the general fire regime in the Southwest (Meyer and Frechette, this issue). The onset of the North American monsoon, usually around the beginning of July, brings higher humidity and intermittent rainfall, dampening grass and dry fuel and generally marking the end of the fire season (and the acceleration of plant growth that provides fuel for the next year's fire season). It is also possible that wildfires affect the regional climate, although this connection is harder to quantify. Large fires inject large quantities of soot and smoke high into the atmosphere. Winds then blow these particulates across the Southwest, so the impact of locally injected particulates can spread far beyond the source. Other sources of particulates, such as widespread air pollution, have been shown to block sunlight and depress precipitation. A study of the South Asian monsoon showed that black carbon soot associated with air pollution decreases the radiative heating of the surface, thereby altering atmospheric stability and largescale temperature gradients that drive monsoon circulations (Ramanathan et al. 2005). Compared to the South Asian brown cloud, southwestern wildfires in most years generate much smaller quantities of particulates that remain airborne for a shorter period of time. However the timing of the southwestern fire season in late spring is potentially just right to affect the onset of the monsoon. The onset date is highly correlated with total seasonal precipitation, such that late onset is usually a precursor of low total summer rainfall (Higgins et al. 1997). We describe here a preliminary assessment of the hypothesis that large spring wildfires could depress monsoonal precipitation, by comparing a 25-yr time series of acreage burned in southwestern wildfires in June with the subsequent precipitation observed in July and August (Van Alst 2009). Data","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174543","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}
Several decades of focused studies on the Valles–Toledo caldera complex and the Jemez Mountains in northern New Mexico have brought about new understanding of the relations of stratigraphic units that record the complex’s evolution. We present here a revision of the formal stratigraphic nomenclature for the Quaternary Tewa Group, an established stratigraphic unit that includes the volcanic and volcaniclastic deposits of the caldera complex. We propose 11 completely new units of member rank, with descriptions of lithology, contact relations, distribution, and type areas. These new members are parts of the Bandelier Tuff, Cerro Toledo, and Valles Rhyolite Formations, and serve to depict the magmatic and geomorphic evolution of the area during and following each of two major caldera-forming episodes. With results from mapping efforts in the Jemez Mountains revealing the broad implications and interrelations of some established units, we redefine one formation (Cerro Toledo Rhyolite) and demote three formal members (El Cajete, Battleship Rock, and Banco Bonito) to bed or flow rank. Because it has been shown repeatedly in published works that one formation (Cerro Rubio Quartz Latite) was originally defined based on erroneous relations, we propose its formal abandonment. Additionally, we propose formal abandonment of one established member (Valle Grande Member of the Valles Rhyolite) because of lack of utility and widespread disuse. Our proposed revisions embody the practices of geologic mappers, and serve to better clarify relations of volcanic and volcaniclastic rocks through the evolution of the Valles–Toledo caldera complex. The new formal stratigraphy that we propose will provide a flexible but robust framework for on-going and future research in the Valles–Toledo caldera complex.
{"title":"Rhyolites and associated deposits of the Valles - Toledo caldera complex","authors":"J. Gardner, F. Goff, S. Kelley, E. Jacobs","doi":"10.58799/nmg-v32n1.3","DOIUrl":"https://doi.org/10.58799/nmg-v32n1.3","url":null,"abstract":"Several decades of focused studies on the Valles–Toledo caldera complex and the Jemez Mountains in northern New Mexico have brought about new understanding of the relations of stratigraphic units that record the complex’s evolution. We present here a revision of the formal stratigraphic nomenclature for the Quaternary Tewa Group, an established stratigraphic unit that includes the volcanic and volcaniclastic deposits of the caldera complex. We propose 11 completely new units of member rank, with descriptions of lithology, contact relations, distribution, and type areas. These new members are parts of the Bandelier Tuff, Cerro Toledo, and Valles Rhyolite Formations, and serve to depict the magmatic and geomorphic evolution of the area during and following each of two major caldera-forming episodes. With results from mapping efforts in the Jemez Mountains revealing the broad implications and interrelations of some established units, we redefine one formation (Cerro Toledo Rhyolite) and demote three formal members (El Cajete, Battleship Rock, and Banco Bonito) to bed or flow rank. Because it has been shown repeatedly in published works that one formation (Cerro Rubio Quartz Latite) was originally defined based on erroneous relations, we propose its formal abandonment. Additionally, we propose formal abandonment of one established member (Valle Grande Member of the Valles Rhyolite) because of lack of utility and widespread disuse. Our proposed revisions embody the practices of geologic mappers, and serve to better clarify relations of volcanic and volcaniclastic rocks through the evolution of the Valles–Toledo caldera complex. The new formal stratigraphy that we propose will provide a flexible but robust framework for on-going and future research in the Valles–Toledo caldera complex.","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174784","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 marine oyster Flemingostrea elegans, n. sp., appears suddenly in lower Coniacian (Upper Cretaceous) strata of central New Mexico. It has no immediate ancestor in the Western Interior of the United States and has not been found anywhere outside central New Mexico. Flemingostrea elegans occurs in nearshore sandstones in the Mulatto Tongue of the Mancos Shale in Socorro County and the Gallup Sandstone of Lincoln County. This medium-sized oyster, with its distinctive terebratuloid fold, is an excellent guide fossil to the lower Coniacian, and is a great aid in distinguishing the Mulatto Tongue from other tongues of the Mancos Shale in Socorro County and in differentiating Coniacian from Turonian sandstones in Lincoln County. It occurs in great numbers, often as articulated shells, and is easily distinguished from all other Turonian through Coniacian oyster species by the fold in its lower valve. Its presence above coal beds in the lower part of the Crevasse Canyon Formation provides definitive evidence for a third cycle of transgression/regression of the western shoreline of the Late Cretaceous Seaway as far south in New Mexico as central Socorro County. The Santonian dwarf species, Flemingostrea nanus (Johnson 1903), known only from Santa Fe County, New Mexico, is redescribed and illustrated. Flemingostrea nanus, F. elegans, n. sp., and the upper Cenomanian F. prudentia (White 1877) are the only species of Flemingostrea known from the Western Interior. Ostrea elegantula Newberry 1876, which has been confused in the literature with F. elegans, n. sp., should be considered formally as a nomen oblitum (a forgotten name) and not used again. Ostrea elegantula was named but not described or illustrated by J. S. Newberry in his geological report of Captain J. N. Macomb’s 1859 San Juan exploring expedition. F. B. Meek, who wrote the paleontological report on the Cretaceous fossils collected on that expedition, did not describe, illustrate, or mention it. Newberry’s type specimens were illustrated in 1883 by C. A. White, again without description. Attempts to recover Newberry’s type locality along the Canadian River, Colfax County, New Mexico, were unsuccessful.
海洋牡蛎Flemingostrea elegans, n.sp .，突然出现在新墨西哥州中部的下Coniacian(上白垩纪)地层中。它在美国西部内陆没有直系祖先，也没有在新墨西哥州中部以外的任何地方发现过。fleminggostrea elegans出现在Socorro县Mancos页岩的Mulatto舌和Lincoln县Gallup砂岩的近岸砂岩中。这种中等大小的牡蛎，具有独特的非脊椎类褶皱，是下科尼亚纪的极好指导化石，是区分索科罗县曼科斯页岩的穆拉托语和其他语言以及区分林肯县科尼亚纪和Turonian砂岩的巨大帮助。它大量出现，通常是铰接的壳，很容易通过其下瓣的褶皱与所有其他Turonian至Coniacian牡蛎物种区分开来。它在克雷瓦斯峡谷地层下部煤层之上的存在，为晚白垩世海道西部海岸线的第三轮海侵/回归提供了明确的证据，从新墨西哥州向南一直延伸到索科罗县中部。圣东尼亚矮种，Flemingostrea nanus (Johnson 1903)，仅在新墨西哥州的圣达菲县已知，被重新描述和说明。fleminggostrea nanus, F. elegans, n. sp.和upper Cenomanian F. prudentia (White 1877)是唯一已知的来自西部内陆的fleminggostrea物种。Ostrea elegantula Newberry 1876，在文献中与F. elegans, n.sp混淆，应该被正式视为nomen oblitum(一个被遗忘的名字)而不再使用。在j·n·马科姆船长1859年圣胡安探险的地质报告中，j·s·纽伯里命名了秀丽Ostrea elegantula，但没有描述或说明。F. B. Meek写了一份关于那次探险所收集的白垩纪化石的古生物学报告，他没有描述、说明或提及这件事。纽伯里的模式标本在1883年由c·a·怀特(C. A. White)绘制，同样没有描述。试图在新墨西哥州科尔法克斯县的加拿大河沿岸恢复纽贝里的类型位置，没有成功。
{"title":"Flemingostrea elegans, n. sp.: guide fossil to marine, lower Coniacian (Upper Cretaceous) strata of central New Mexico","authors":"S. Hook","doi":"10.58799/nmg-v32n2.35","DOIUrl":"https://doi.org/10.58799/nmg-v32n2.35","url":null,"abstract":"The marine oyster Flemingostrea elegans, n. sp., appears suddenly in lower Coniacian (Upper Cretaceous) strata of central New Mexico. It has no immediate ancestor in the Western Interior of the United States and has not been found anywhere outside central New Mexico. Flemingostrea elegans occurs in nearshore sandstones in the Mulatto Tongue of the Mancos Shale in Socorro County and the Gallup Sandstone of Lincoln County. This medium-sized oyster, with its distinctive terebratuloid fold, is an excellent guide fossil to the lower Coniacian, and is a great aid in distinguishing the Mulatto Tongue from other tongues of the Mancos Shale in Socorro County and in differentiating Coniacian from Turonian sandstones in Lincoln County. It occurs in great numbers, often as articulated shells, and is easily distinguished from all other Turonian through Coniacian oyster species by the fold in its lower valve. Its presence above coal beds in the lower part of the Crevasse Canyon Formation provides definitive evidence for a third cycle of transgression/regression of the western shoreline of the Late Cretaceous Seaway as far south in New Mexico as central Socorro County. The Santonian dwarf species, Flemingostrea nanus (Johnson 1903), known only from Santa Fe County, New Mexico, is redescribed and illustrated. Flemingostrea nanus, F. elegans, n. sp., and the upper Cenomanian F. prudentia (White 1877) are the only species of Flemingostrea known from the Western Interior. Ostrea elegantula Newberry 1876, which has been confused in the literature with F. elegans, n. sp., should be considered formally as a nomen oblitum (a forgotten name) and not used again. Ostrea elegantula was named but not described or illustrated by J. S. Newberry in his geological report of Captain J. N. Macomb’s 1859 San Juan exploring expedition. F. B. Meek, who wrote the paleontological report on the Cretaceous fossils collected on that expedition, did not describe, illustrate, or mention it. Newberry’s type specimens were illustrated in 1883 by C. A. White, again without description. Attempts to recover Newberry’s type locality along the Canadian River, Colfax County, New Mexico, were unsuccessful.","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2010-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71174917","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}
Newly discovered pumice beds in axial-fluvial strata of the Pliocene–lower Pleistocene Camp Rice and Palomas Formations in the southern Rio Grande rift are geochemically correlated to a previously dated 3.1-Ma pumice bed at Hatch Siphon. The Lucero pumice in the Dona Ana Mountains is 1–1.5 m thick and consists of granule- and pebble-sized pumice intercalated with fluvial sand, whereas the Mud Springs pumice along the southeastern flank of the Mud Springs Mountains is 10 cm thick and is composed of sand-sized pumice. Samples from all three sites consist of vesicular, rhyolitic glass fragments and are compositionally identical, particularly with respect to Fe, Ca, and Mn, suggesting derivation from the same 3.1-Ma volcanic eruption. The composition and age of this erupted material is consistent with derivation from the Grants Ridge area, south of Mt. Taylor, implying transport to the ancestral Rio Grande via the Rio Puerco drainage system. If the correlation is correct, the Lucero pumice, along with a bed of 1.6-Ma pumice and the constructional top of the Camp Rice Formation (~0.8 Ma), provide chronologic constraints on the rate of onlap of the northwestern Dona Ana Mountains by axial-fluvial sediment of the Camp Rice Formation. From 3.1 to 1.6 Ma, the sediment accumulation rate was 46.7 m/ Ma, and the lateral rate of eastward onlap was 2 km/Ma. The corresponding values diminished to 18.8 m/Ma and 0.89 km/Ma, respectively, from 1.6 to 0.8 Ma, perhaps due to activity on the Jornada fault, which borders the northern Dona Ana Mountains. If the correlation between the Mud Springs pumice and 3.1-Ma Hatch Siphon pumice is correct, then the Mud Springs pumice provides a reliable chronologic marker within the Palomas Formation that can be compared to existing biostratigraphic data from the same region. The 3.1-Ma Mud Springs pumice is located within the stratigraphic range of the vertebrate collection of Lucas and Oakes (1986) and is consistent with their interpretation of the fauna as medial Blancan in age (~3 Ma). In contrast, the vertebrate collection of Repenning and May (1986), which has been interpreted as very early Blancan II in age (~4.5 Ma), seems anomalously old, given the fact that it is only ~20 m beneath the Mud Springs pumice.
{"title":"New sites of 3.1-Ma pumice beds in axial fluvial strata of the Camp Rice and Palomas formations, southern Rio Grande rift","authors":"G. Mack, N. Dunbar, R. Foster","doi":"10.58799/nmg-v31n2.31","DOIUrl":"https://doi.org/10.58799/nmg-v31n2.31","url":null,"abstract":"Newly discovered pumice beds in axial-fluvial strata of the Pliocene–lower Pleistocene Camp Rice and Palomas Formations in the southern Rio Grande rift are geochemically correlated to a previously dated 3.1-Ma pumice bed at Hatch Siphon. The Lucero pumice in the Dona Ana Mountains is 1–1.5 m thick and consists of granule- and pebble-sized pumice intercalated with fluvial sand, whereas the Mud Springs pumice along the southeastern flank of the Mud Springs Mountains is 10 cm thick and is composed of sand-sized pumice. Samples from all three sites consist of vesicular, rhyolitic glass fragments and are compositionally identical, particularly with respect to Fe, Ca, and Mn, suggesting derivation from the same 3.1-Ma volcanic eruption. The composition and age of this erupted material is consistent with derivation from the Grants Ridge area, south of Mt. Taylor, implying transport to the ancestral Rio Grande via the Rio Puerco drainage system. If the correlation is correct, the Lucero pumice, along with a bed of 1.6-Ma pumice and the constructional top of the Camp Rice Formation (~0.8 Ma), provide chronologic constraints on the rate of onlap of the northwestern Dona Ana Mountains by axial-fluvial sediment of the Camp Rice Formation. From 3.1 to 1.6 Ma, the sediment accumulation rate was 46.7 m/ Ma, and the lateral rate of eastward onlap was 2 km/Ma. The corresponding values diminished to 18.8 m/Ma and 0.89 km/Ma, respectively, from 1.6 to 0.8 Ma, perhaps due to activity on the Jornada fault, which borders the northern Dona Ana Mountains. If the correlation between the Mud Springs pumice and 3.1-Ma Hatch Siphon pumice is correct, then the Mud Springs pumice provides a reliable chronologic marker within the Palomas Formation that can be compared to existing biostratigraphic data from the same region. The 3.1-Ma Mud Springs pumice is located within the stratigraphic range of the vertebrate collection of Lucas and Oakes (1986) and is consistent with their interpretation of the fauna as medial Blancan in age (~3 Ma). In contrast, the vertebrate collection of Repenning and May (1986), which has been interpreted as very early Blancan II in age (~4.5 Ma), seems anomalously old, given the fact that it is only ~20 m beneath the Mud Springs pumice.","PeriodicalId":35824,"journal":{"name":"New Mexico Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2009-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71173986","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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