In this new volume, Poag has revised and updated the atlas, incorporating three decades of extensive data collections from the open Gulf and from an additional seventeen estuarine systems to cover species of benthic foraminifera from more than eight thousand sample stations. Benthic Foraminifera of the Gulf of Mexico features 68 plates of scanning electron photomicrographs, 64 color figures, and a large color foldout map, indicating species distribution of forams.
This book is designed to aid students and teachers of geology, biology, oceanography, and ecology, as well as micropaleontologists in government and industry laboratories, and other researchers and consultants who have an interest in benthic ecology or paleoecology.
In this new volume, Poag has revised and updated the atlas, incorporating three decades of extensive data collections from the open Gulf and from an additional seventeen estuarine systems to cover species of benthic foraminifera from more than eight thousand sample stations. Benthic Foraminifera of the Gulf of Mexico features 68 plates of scanning electron photomicrographs, 64 color figures, and a large color foldout map, indicating species distribution of forams.
This book is designed to aid students and teachers of geology, biology, oceanography, and ecology, as well as micropaleontologists in government and industry laboratories, and other researchers and consultants who have an interest in benthic ecology or paleoecology.
Benthic Foraminifera of the Gulf of Mexico: Distribution, Ecology, Paleoecology
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In this new volume, Poag has revised and updated the atlas, incorporating three decades of extensive data collections from the open Gulf and from an additional seventeen estuarine systems to cover species of benthic foraminifera from more than eight thousand sample stations. Benthic Foraminifera of the Gulf of Mexico features 68 plates of scanning electron photomicrographs, 64 color figures, and a large color foldout map, indicating species distribution of forams.
This book is designed to aid students and teachers of geology, biology, oceanography, and ecology, as well as micropaleontologists in government and industry laboratories, and other researchers and consultants who have an interest in benthic ecology or paleoecology.
Product Details
| ISBN-13: | 9781623492137 |
|---|---|
| Publisher: | Texas A&M University Press |
| Publication date: | 03/15/2015 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 256 |
| File size: | 87 MB |
| Note: | This product may take a few minutes to download. |
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Benthic Foraminifera of the Gulf of Mexico
Distribution, Ecology, Paleoecology
By C. Wylie Poag
Texas A&M University Press
Copyright © 2015 C. Wylie PoagAll rights reserved.
ISBN: 978-1-62349-213-7
CHAPTER 1
PART I Ecology and Distribution of Predominant Genera
INTRODUCTION
Environmental Characteristics of the Gulf of Mexico
The Gulf of Mexico is classified as a small ocean, ninth largest on the globe. Its waters cover approximately 1,540,000 km2, constitute a volume of more than 300,000,000 km3, and reach depths of 4,384 m (Gore 1992; Moretzsohn, Sánchez Chávez, and Tunnell 2012). The marine shoreline, exclusive of estuaries, is ~5,700 km long. In order to understand relationships between benthic foraminiferal communities and the varied environments of this vast region, the major environmental properties must be examined. These properties include physiography, general geology, and climate of surrounding shores, as well as the major environmental features of the marine realm: bottom physiography and geology, climate, circulation, water masses, and the resulting biogeographic character. Environmental data are plentiful for the northern Gulf margin. This coastal region is heavily populated and includes such large cities as Tampa, New Orleans, and Houston. In addition, the northern coastal plain and submerged continental margin is one of the richest US domestic petroleum provinces. More than 41,000 Gulf offshore wells and 1,300 fields produce ~25% of US domestic oil and gas (Shirley 2003; Huffman, Warwick, and Finch 2011). Other critical industries and economic activities include fishing, merchant shipping, maritime vessel construction, and tourism (Adams, Hernandez, and Lee 2009; Yoskowitz 2009). Consequently, vast quantities of detailed information on the climatology, geology, and biology of the Gulf of Mexico have been produced over the years by numerous agencies and institutions.
Conversely, the southern Gulf margin has received relatively little attention. The Mexican coast is more sparsely populated, although coastal and offshore petroleum exploration and production, as well as commercial fishing and tourism, are important aspects of the Mexican economy (Yañez-Arancebia et al. 2009). As a result, environmental data for this southern area are sparse and applicable only to broad generalizations or to specific localities. The central (deeper) parts of the Gulf also have been somewhat neglected. The general geologic framework of the Gulf and its climate, sediment distribution, and pattern of surface currents are well known, however, and more specific data have been acquired for scattered localities. On the other hand, knowledge of physical, chemical, and biological oceanography on a Gulf-wide scale is rudimentary.
Physiography and Geology of the Gulf Coastal Plain
A brief review of the physiography and geology of the Gulf Coastal Plain is important because many of the sediments and dissolved minerals that provide nutrients, substrates, and test materials for benthic foraminifera are derived from coastal rocks. Furthermore, topographic and geologic features of the Gulf Coastal Plain greatly influence the courses of numerous rivers that freshen coastal waters and form extensive estuarine and deltaic biotopes. Many coastal physiographic features also extend onto the continental shelf, where they influence foraminiferal distributions. Murray (1961) has provided a detailed review of the physiography and geology of the coastal plain.
The Gulf of Mexico lies within a semi-enclosed basin (Figures 1–3), the eastern margin of which is formed by the Florida peninsula. This peninsula of coastal lowlands and plains, approximately 90 km across and 250 km in length, is encompassed entirely within the Gulf Coastal Plain Province. Thick beds of Cenozoic limestone underlie most of the peninsula and are generally covered by quartz sands of Pleistocene origin. The surface of this region is drained on the Gulf side principally by the Caloosahatchee and Suwannee rivers, but other rivers and underground cavities in the soluble limestones provide additional drainage (Kohout, Henry, and Banks 1977; Scott 2011; Figure 2; Appendix 1, Figure 1).
The Gulf shoreline of Florida is extensive (~595 km long) and complex. It begins in the south with the Florida Keys, a crescentic chain of low-relief carbonate islands, which forms the boundary between shallow Florida Bay and the deep Straits of Florida (Figure 4). Northward on the mainland, a series of vast island-dotted mangrove swamps and forests lines the Florida shore up to about Charlotte Harbor (Figure 2). Charlotte Harbor and Tampa Bay are the two major west Florida estuaries, formed by the lower reaches of the Peace River and Hillsborough River, respectively (Brooks 2011; Figure 2; Appendix 1, Figure 1). These two bays are rimmed by siliciclastic shorelines associated with sandy, quartzose, barrier beaches. Northward, from Tampa Bay to the eastern end of the Florida panhandle (the Big Bend coast), the 200 km long shoreline is characterized by exposed carbonate bedrock and sediment-starved salt marshes, and lacks bordering barrier islands (Hine and Locker 2011). The panhandle coast of Florida (~120 km between Cape San Blas and the Alabama state line) displays characteristic siliciclastic deltas, bays, marshes and barrier beaches along a widening segment of coastal plain (~120 km wide).
A much wider siliciclastic coastal plain segment extends from Alabama to the US-Mexico border (Figure 3). The shoreline in this region comprises deltaic and coastwise plains bordered by salt marshes, a few mangroves, and siliciclastic barrier beaches. Inland is a series of coastwise Pleistocene alluvial terraces, which are bounded landward by belted topography developed on outcropping bands of Cenozoic and Upper Cretaceous sedimentary strata. At its widest point, this segment of the Gulf Coastal Plain extends inland for more than 400 km, reaching from the Mississippi Delta to southern Missouri and Kentucky. This northern coastal segment, therefore, provides the greatest variety and volume of sediments to the Gulf basin (van Andel 1960).
Principal freshwater drainage of this wide northern coastal plain segment begins to the east with the Flint-Chattahoochee-Apalachicola River system of northern Florida and the Alabama-Tombigbee-Mobile River system of Alabama (Murray 1961; Figure 2; Appendix 1, Figure 1). These rivers arise in the Appalachian uplands of Alabama and Georgia. Through the middle of the northern coastal plain courses the Mississippi River, which enters the Gulf through a huge birdfoot delta system (Figures 1–4). The Mississippi is by far the most significant river system entering the Gulf, deriving its waters from the entire heartland of the United States between the Appalachian Mountains and Rocky Mountains. The Mississippi drains 41% of the total area of the contiguous United States (>5 million km2). Annual contribution of Mississippi River sediments to the Gulf of Mexico amounts to more than 600 million metric tons (Moody 1967). Westward from the Mississippi Delta, the Sabine, Neches, Trinity, Brazos, Colorado, Guadalupe, San Antonio, Rio Grande, and several smaller rivers wind across the broad (~100–220 km wide) Texas Coastal Plain, carrying sediments from Cenozoic and Cretaceous outcrops to the northwestern Gulf (Figure 2; Appendix 1, Figure 1).
The shoreline features of this wider northern segment of coastal plain begin in panhandle Florida as a series of narrow siliciclastic beaches, dunes, barrier islands, and low salt marshes. These give way westward to the large Mobile Bay estuary and to coastal bays and salt marshes surrounding the Mississippi Delta (Figures 2, 4). Farther westward, Texas rivers form a series of marshy estuarine embayments and lagoons behind extensive, siliciclastic, barrier beaches. These estuaries entrap much of the river-borne detritus, permitting only a small volume to reach the continental shelf (van Andel 1960; Figure 2).
The Mexican Coastal Plain, from the Rio Grande to just east of Laguna de Términos, is much narrower than other coastal-plain segments (Figure 3), with maximum width of ~90 km. The inner edge of the coastal plain here is bordered by the Sierra Madre Oriental and the Chiapas Highlands. Cenozoic sedimentary strata underlie the bulk of the Mexican Coastal Plain, but at its inland edge and in the adjacent mountains, Cretaceous and Jurassic sedimentary beds crop out. At two locations, one just north of Tampico and the other southeast of Veracruz, igneous and volcanic rocks reach the Gulf shore and narrow the coastal plain to ~10 km (Figure 3). The principal rivers of this coastal segment, the Pánuco and Tamesi, have headwaters in the Sierra Madre Oriental, and bring relatively unaltered Mesozoic sediments into the western Gulf (Figure 2; Appendix 1, Figure 1). Southwest of Laguna de Términos, the Grijalva and Usumacinta rivers have constructed a vast alluvial plain similar to that surrounding the Mississippi Delta (Figures 2, 3; Appendix 1, Figure 1).
From the Rio Grande to Laguna de Términos, the Mexican shoreline is largely a series of narrow siliciclastic beaches and dunes interrupted by elongate shallow lagoons (lagunas), barrier bars, and river-mouth marshes. The major exception is the stretch of volcanic rocks southeast of Veracruz (Figure 3). Nearly all remaining coastal wetlands along the Mexican Gulf Coast are fringed by extensive mangrove swamps and forests (Snedaker 1993; Childers et al. 1999). The Laguna de Términos basin alone, for example, contains more mangrove wetlands than the entire US Gulf Coast.
East of Laguna de Términos, limestone lowlands of the Yucatán Peninsula constitute the southeastern rim of the Gulf, and the coastal plain broadens to 230 km. This peninsula is largely drained underground through systems of caverns, sinkholes (cenotes), and other carbonate solution features. No significant rivers are present in this vast region, but a few small streams and lakes occur along the 280 km shoreline. The western shore of the Yucatán Peninsula is rather uniform, consisting of carbonate sand beaches interrupted by minor irregularities, narrow salt marshes, mangrove swamps, and the narrow Laguna de Celestun. In contrast, the northern Yucatán coast is embayed by three narrow, coastwise lagunas (Chelem, Dzilam, and Yalahua), and the extensive, hypersaline, Ria Lagartos, all of which are protected from the open Gulf by barriers of carbonate sand (Pennock et al. 1999; Figure 2).
Physiography of the Gulf Floor
The physiography of the Gulf floor largely determines distribution routes and final location of siliciclastic deposits debouched by coastal rivers. Submerged physiographic features also greatly influence distribution and stability of benthic communities, because the width, depth, and topographic relief, especially of the continental shelves, modify effects of currents, waves, tides, sediment distribution, and light penetration. The large physiographic features of the Gulf are well known (Ewing, Ericson, and Heezen 1958; Murray 1961; Bouma 1968; Bryant et al. 1968, 1969; Ballard and Uchupi 1970; Bergantino 1971; Garrison and Martin 1973; Stuart and Caughey 1977; Martin and Bouma 1979; Buster and Holmes 2011; Figures 3, 4). Seismic-reflection and fathometer profiles of the seafloor have been collected from every part of the open Gulf, and many areas have been studied in great detail with multibeam sonar surveys. For purposes of this synthesis, I describe chiefly those physiographic features that appear to have some influence on the distribution of benthic foraminifera.
Seaward of the coastal bays, estuaries, barrier-island lagoons, mangrove swamps, and river-mouth deltas, three broad, gently sloping segments of the continental shelf extend out to a depth of about 200 m (locally the shelf edge is as shallow as 60 m; Figure 4). Seaward of the western Florida shoreline, the West Florida Shelf is broad (90–110 km), but narrows to 20–40 km west of Cape San Blas (Figures 3, 4). The Texas-Louisiana Shelf (20–90 km wide) extends from Mobile Bay to the Rio Grande. The narrow (10–20 km wide), more steeply sloping East Mexico Shelf is separated by only a narrow coastal plain (10–60 km) from the elevated Sierra Madre Oriental (Figures 3, 4). The 80–120 km wide Campeche Shelf (Banco de Campeche) borders the northern and western parts of the Yucatán Peninsula. The relatively smooth surfaces of these continental shelves are interrupted by submerged or emergent banks and reefs, and by submerged ancient shoreline features (Ballard and Uchupi 1970; Poag 1972, 1973; Rezak, Bright, and McGrail 1985; Tunnell, Chávez, and Withers 2007; Figure 5).
Between depths of about 200 m and 2000 m, the more steeply inclined continental slope rims the Gulf (Figures 3, 4). The continental slope off Louisiana, Texas, and Campeche is quite rugged (Figures 3, 6). Diapiric intrusions arising from subsurface salt masses form numerous submerged banks, ridges, and domes (Bryant et al. 1990; Diegel et al. 1995). Subsurface salt withdrawal into these diapiric structures has created a complex array of intraslope basins (Bouma et al. 1975; Shokes et al. 1977; Reynolds 1982; Prather et al. 1988; Pilcher and Blumstein 2007; Figure 6). On the continental slope of eastern Mexico, a series of elongate, parallel ridges represent compressional folds of thick sedimentary beds that lie above an undeformed salt layer (Bryant et al. 1968; Buffler et al. 1979; Watkins et al. 1979; Bryant et al. 1990; Figure 3). The mouths of several major submarine canyons indent the lower margin of the Gulf continental slope: DeSoto Canyon off northern Florida; Mississippi Trough off the central Louisiana coast; Alaminos, Bryant, Cortez, Farnella, Green, Keathley, and Perdido canyons off Louisiana and Texas; and Campeche Canyon along the western margin of the Campeche Shelf (Lee 1990; Satterfield and Behrens 1990; Lee, Watkins, and Bryant 1996; Tripsanas 2003; Tripsanas, Bryant, and Phaneuf 2004; Tripsanas et al. 2007; Figures 3, 6). The basinward edge of the continental slope everywhere except off the Mississippi Delta and eastern Mexico is formed by steep escarpments: West Florida Escarpment, Sigsbee Escarpment, Perdido Escarpment, and Campeche Escarpment (Figures 3, 4, 6). The West Florida Escarpment is particularly notable for its steep slope (45°), erosional exposure of a 3,400 m thick section of Lower Cretaceous limestones, and the presence of several hypersaline brine seeps along its base (Paull et al. 1984, 1990).
Next, sloping more gently into the center of the Gulf basin, the continental rise is rather uniformly smooth on the west and northwest (Western Gulf Rise), but to the east a huge pile (~360,000 km2) of Mississippi River sediments forms the cone-shaped Mississippi Fan (Bouma, Stetling, and Coleman 1985; Twichell 2011; Figures 3, 4). The deepest part of the Gulf basin (>3,600 m) covers ~150,000 km2 in the west-central part of the Gulf. This relatively flat region is called the Sigsbee Plain (Figures 3, 4). Even here, however, underlying mobile salt beds have produced the well-known Sigsbee Knolls and other bottom prominences. A relatively small area of abyssal seafloor in the southeastern Gulf, between the Florida and Campeche escarpments, is known as the Florida Plain. Several sediment-capped knolls are present here also, but they are of igneous and metamorphic origin (Pyle et al. 1969; Martin and Bouma 1979; Buffler, Schlager et al., 1984).
The southeastern margin of the Gulf basin is formed by a submerged ridge connecting Yucatán to the island of Cuba (Figures 3, 4). This ridge forms a sill approximately 1,500–2,000 m below sea level, which prevents the deeper waters of the Caribbean Sea from directly entering the Gulf. Between Florida and Cuba, the submerged rim of the Gulf is even shallower, rising to about 1,000 m in the Straits of Florida. This sill allows only shallow Gulf water masses to exit into the Atlantic Ocean (Schroeder, Berner, and Nowlin 1974; Carder et al. 1977; Hamilton 1990; Schmitz et al. 2005; Sturges 2005).
Climate
General climate of the Gulf of Mexico is significant because it controls surface temperature, relative humidity, and precipitation, and thereby serves as a basis for differentiating biogeographic provinces. Of these factors, temperature is thought by many to have the strongest influence on the distribution of marine organisms because it directly affects rates of chemical reactions in the water and within organisms, exerting powerful control over activity rates, metabolic functions, reproduction, and growth rates.
The Gulf of Mexico lies between latitudes 18° N and 30° N, a tropical to subtropical region of generally abundant rainfall and high humidity (Trewartha 1954; Figure 7). Five rather clearly defined regions of continental climate can be recognized in the surrounding coastal plain. The largest single climatic region begins with the Florida peninsula north of Charlotte Harbor, and extends through Texas to just above its border with Tamaulipas. This is a humid subtropical region with average summer temperature around 25–27 °C. Normal diurnal temperature variation is 8–17 °C. Throughout most of this region, rainfall is the dominant form of precipitation and averages 100–150 cm per year, except in two places. The first, near the coast, from the Mississippi Delta to about Tallahassee, Florida, is a zone of higher rainfall that averages 150–200 cm per year. The second place is the much drier southwestern Texas coast, which averages only 50–100 cm per year.
(Continues...)
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Table of Contents
Contents
Preface,Acknowledgments,
PART I. ECOLOGY AND DISTRIBUTION OF PREDOMINANT GENERA,
Introduction,
Environmental Characteristics of the Gulf of Mexico,
Physiography and Geology of the Gulf Coastal Plain,
Physiography of the Gulf Floor,
Climate,
Water Mass Stratification and Current Circulation,
Sediments of the Gulf Floor,
Marine Biogeography,
Previous Studies of Gulf Benthic Foraminifera,
Generic Predominance Facies of Modern Gulf Benthic Foraminifera,
Estuarine Biotopes,
Continental Shelf Biotopes,
Continental Slope Biotopes,
Continental Rise and Florida Plain Biotopes,
Sigsbee Plain and Mississippi Fan Biotopes,
Relationships Between Generic Predominance Facies and Environmental Properties,
Salinity,
Temperature,
Substrate,
Water Mass Composition,
Food Supply, Dissolved Oxygen, and Water Clarity,
Bottom Topography,
Holocene Sea-level Rise,
Generic Predominance Diversity,
Fossil Foraminifera and Paleoecological Interpretation,
Conclusions,
PART II. DESCRIPTION AND ILLUSTRATION OF DIAGNOSTIC SPECIES,
Taxonomy and Distribution,
Plates: Scanning Electron Photomicrographs,
Appendix 1. Supplementary Figures and Tables,
Appendix 2. List of Cosmopolitan Benthic Foraminiferal Species,
Appendix 3. List of Regional Benthic Foraminiferal Species,
Appendix 4. List of Endemic Benthic Foraminiferal Species,
Appendix 5: List of Relict Benthic Foraminiferal Species,
References,
Index,
Interviews
Woods Hole, Massachusetts