Baton Rouge 30 x 60 Minute Geologic Quadrangle · BATON ROUGE, LOUISIANA 30091-A1-100K BATON ROUGE,...
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Pp Ppl Ppe Ppbc Ppbce Ppbcl Ppav Ppbe Pph Hb Hma Hrd Hrl Hrm Hac Had Hal Hala Hua Hcr Hmm u Hmm l 3 Hmc l 3 Hmd l 3 Hml l 3 3 Hmc u 3 Hmd u 3 Hml u 3 Hmm 1 Hmc 1 Hmd 1 Hml 1 Hlm Hlc Hll [Peoria Loess] [Peoria Loess] Hb Hb Hs Hb U D U D U D U D U D VERMILLION PARISH IBERIA PARISH LAFAYETTE PARISH ST MARTIN PARISH IBERIA PARISH ST MARTIN PARISH IBERIA PARISH PARISH IBERVILLE IBERIA PARISH IBERVILLE PARISH ASSUMPTION PARISH IBERVILLE PARISH ASCENSION PARISH EAST BATON ROUGE P ARISH WEST BATON ROUGE PARISH IBERVILLE PARISH WEST BATON ROUGE IBERVILLE PARISH PARISH POINTE COUPEE PARISH IBERVILLE P ARISH ST MARTIN P ARISH ST LANDRY P ARISH ST LANDRY P ARISH ST MARTIN P ARISH LAFAYETTE PARISH WEST BATON ROUGE PARISH EAST BATON ROUGE PARISH BATON ROUGE Port Allen Plaquemine White Castle Maringouin Arnaudville Breaux Bridge Lafayette St Martinville New Iberia Donaldsonville Hac Hac Hac Hac Hac Hac Hac Hac Hac Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Had Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hal Hala Hala Hala Hala Hala Hala Hala Hala Hala Hcr Hcr Hcr Hcr Hcr Hcr Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hua Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hlm Hld Hld Hld Hld Hld Hll Hll Hll Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hb Hmm1 Hmm1 Hmm1 Hmm1 Hmm1 Hmm1 Hmm1 Hmm1 Hmm1 Hmc1 Hmc1 Hmc1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hml1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hmd1 Hs Hs Hs Hs Hb Hmm3u Hmm3u Hmm3u Hmm3u Hmm3u Hmm3u Hmm3u Hmm3u Hmm3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmc3u Hmd3u Hmd3u Hmd3u Hmd3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hma Hma Hma Hma Hma Hb Hma Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmm3l Hmc3l Hmc3l Hml3l Hml3l Hml3l Hml3l Hml3l Hml3l Hml3l Hml3l Hml3l Hml3l Hmd3l Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hml3u Hrm Hrm Hrm Hrm Hrm Hrm Hrm Hb Hrl Hrd Ppbce Ppbce Ppbce Ppbce Ppbcl Ppbcl Ppbcl Ppbcl Ppbcl Ppbcl Hmm3l Ppav Ppav Ppav Ppav Ppav Ppav Ppbe Ppbe Ppbe Ppbe Pph Pph Pph Pph Pph Pph Pph Pph Pph Pph Pph Pph Pph Hala B a y o u P o rta g e M IS S IS S I P P I R I V E R MISSISSIP PI R I V E R B ayo u L a f o u r c h e G r a n d L ake C h i c o t P a s s A T C H A F A L A Y A BA SIN M A IN C H A N N E L L a k e F a u s s e P o i n t e D a u t e r iv e L a k e B ayou T ech e B a yo u T e c h e B a y o u T e c h e V e r m i l i o n R i v e r A t c h a f a laya R iver W hisky B a y Pilot Ch a n n el B a yo u S o r r e l B ayou P l a q u e m ine INTRACOASTAL WATERWAY H e n d e r s o n S w a m p Lake Fausse Pointe B a y o u M a r i n g o u i n Ba y o u G r o ss e T e t e V e r m il i o n R iver 91°00' 30°30' 30°00' 91°00' 15' 30' 45' 92°00' 30°00' 92°00' 30°30' 45' 30' 15' SCALE 1:100,000 Base map from U.S. Geological Survey, 1:100,000-scale Digital Line Graphs (100K DLG) Universal Transverse Mercator Projection, Zone 15 1927 North American Datum (NAD 27) Contour Interval 10 meters National Geodetic Vertical Datum 1929 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Kilometers 1 2 1 4 3 6 5 8 7 10 9 12 11 13 Miles BATON ROUGE, LOUISIANA 30091-A1-100K BATON ROUGE, LOUISIANA 30 x 60 MINUTE GEOLOGIC QUADRANGLE SERIES Baton Rouge 30 x 60 Minute Geologic Quadrangle 2000 Produced and published by the Louisiana Geological Survey 208 Howe-Russell Geoscience Complex, Louisiana State University P.O. Box G, Baton Rouge, LA 70893 • 225/388-5320 • www.lgs.lsu.edu Production of this map was supported by the U.S. Geological Survey, Department of the Interior, under Assistance Award No. 1434-93-A-1154 and by the Office of Mineral Resources, Louisiana Department of Natural Resources. Copyright ©2000 by the Louisiana Geological Survey Geology by: Paul V. Heinrich and Whitney J. Autin GIS compilation by: S. Ahmet Binselam and R. Hampton Peele Cartography by: John Snead and Robert Paulsell New Roads Baton Rouge Crowley 30° 32° 94° 92° 90° 0 50 miles Amite Bogalusa Ville Platte Pontchatoula L O U I S I A N A Published (2000) in production 30 x 60 Minute Geologic Quadrangles De Ridder Lake Charles Gulfport Hua Hb Hrm Hrl Hrd Hmm3u Hmc3u Hmd3u Hmd3l Hmm3l Hmc3l Hml3l Hs Ppbce Ppbcl Ppav Ppbe Pph Hcr Hml3u Hma Correlation of Map Units Description of Map Units HOLOCENE Undifferentiated alluvium of small upland streams—alluvial deposits of minor creeks and streams filling valleys cut into older deposits. The modern flood plain within these valleys constitutes the surface of these deposits. The lithology reflects the lithology of the older deposits from which they have been eroded and reworked. Backswamp deposits—Holocene deposits of the Mississippi and Atchafayala rivers. They consist of fine-grained, usually clayey and often organically rich sediments that underlie flood basins between meander-belts. Small river deposits, undifferentiated—undifferentiated alluvial deposits of small rivers consisting of recognizable but unmapped natural levees, distributaries, and abandoned channels. River channel remnants—sinuous tonal pattern interpreted to be an abandoned river channel, buried beneath backswamp and natural levee deposits. ATCHAFALAYA RIVER DEPOSITS Crevasse complex of the Atchafalaya River—silty, sometimes sandy, deposits of crevasse splays originating from the Atchafalaya River. Distributary complex of the Atchafalaya River—silty to sandy, natural levee deposits of distributaries originating from the Atchafalaya River. Natural levee deposits of the Atchafalaya River—the silty to sometimes sandy overbank deposits that compose the low natural levees that flank the Atchafalaya River. Lacustrine deposits—fine-grained, generally clayey deposits of areas created by the infilling of lakes by Atchafalaya River distributaries. LAFOURCHE DELTA LOBE DEPOSITS Lafourche meander-belt—clayey deposits filling the abandoned main Mississippi River channel of the Lafourche delta lobe. Locally, these deposits may include younger natural levee and overbank deposits of the modern Bayou Lafourche that are too small to map at this scale. Distributary complex of the Lafourche delta lobe—silty to clayey natural levee deposits of distributaries originating from the Lafourche meander-belt. Natural levee deposits of the Lafourche meander-belt —the silty to sometimes sandy deposits that compose the low natural levees that flank the Lafourche meander-belt and it's main distributary channels. MISSISSIPPI RIVER DEPOSITS Mississippi River meander-belt No. 1—point-bar channel deposits and abandoned channels associated with the modern course of the Mississippi River. Crevasse complex of Mississippi River meander-belt No. 1—silty to sandy deposits of crevasse splays originating from meander-belt No. 1. Distributary complex of Mississippi River meander-belt No. 1—silty to clayey, natural levee deposits of distributaries originating from meander-belt No. 1. Natural levee complex of Mississippi River meander-belt No. 1—silty to sandy overbank deposits that compose the low natural levees flanking the Mississippi River meander-belt No. 1. Upper (Bayou Teche) occupation of Mississippi River meander-belt No. 3 —point-bar channel deposits associated with the relict Bayou Teche course of the Mississippi River. This is the most recent meander-belt 3 occupation. Crevasse complex of Bayou Teche meander-belt—silty to sandy deposits of crevasse splays originating from the Bayou Teche occupation of meander-belt No. 3. Distributary complex of Bayou Teche meander-belt—silty to clayey, natural levee deposits of distributaries originating from the Bayou Teche occupation of meander-belt No. 3. Natural levee complex of Bayou Teche meander-belt—silty to sometimes sandy overbank deposits that compose the low natural levees that flank the Bayou Teche occupation of meander-belt No. 3. Distributary complex occupied by the Mississippi and Atchafalaya Rivers—natural levees and abandoned course of a relict distributary system of the Bayou Teche meander-belt. Segments of the abandoned course have been either reoccupied or buried by distributaries of the Atchafalaya River. Lower (Bayou Portage) meander-belt of Mississippi River meander-belt No. 3 —point bar deposits associated with the relict Bayou Portage occupation of the Mississippi River meander belt No. 3. Crevasse complex of Bayou Portage meander-belt—silty to sandy deposits of crevasse splays originating from the Bayou Portage occupation of meander-belt No. 3. Distributary complex of Bayou Portage meander-belt—silty to clayey, natural levee deposits of distributaries originating from the Bayou Portage occupation of meander-belt No. 3. Natural levee complex of Bayou Portage meander-belt—generally silty overbank deposits that compose the low natural levees that flank the Bayou Portage meander-belt. RED RIVER DEPOSITS Meander-belt of the Teche course of the Red River—brownish red point bar and overbank deposits of the relict course of the Red River that have accumulated within the Bayou Teche occupation of Mississippi River meander-belt No. 3. Locally, these deposits may include younger natural levee and overbank deposits of the modern Bayou Teche that are too small to map at this scale. Natural levee complex of the Teche course of the Red River—scattered natural levee deposits composed of silty, reddish-brown sediments that have locally buried parts of the Bayou Teche natural levees. Major distributary channel of the Teche course of the Red River—clayey to silty deposits that fill an abandoned Teche–Red River distributary along Catahoula Coulee. PLEISTOCENE LOESS Peoria Loess—Eolian silt veneer of late Wisconsin age mantling Pleistocene strata. Loess is depicted where the total thickness is 1 meter or greater. PRAIRIE ALLOGROUP A diverse depositional sequence of late to middle Pleistocene deposits of the Mississippi River, its tributaries, and coastal plain streams; includes terraces, fluvial (meander-belt, backswamp, and braided-stream), colluvial, estuarine, deltaic, and marine units deposited over a considerable part of the late Pleistocene (Wisconsin to Sangamon). Surfaces generally show little dissection and are topographically higher than the Holocene units. Multiple levels are recognized along alluvial valleys and coast-parallel trends. The Prairie is divided into two temporal phases of deposition. PRAIRIE ALLOGROUP, LATE SANGAMON—younger of the Prairie Allogroup temporal phases. Alluvial deposits of ancestral late Pleistocene streams. In the coast-parallel Prairie the unit consists of meander-belt deposits of the late Pleistocene Mississippi River, and deposits of the late Pleistocene coastal plain streams. Deposits associated with these valleys are commonly found within the upper portions of the drainage basins. The surface is blanketed by Peoria Loess near the loess source (the Mississippi River flood plain), and the sediments at the top of the unit range from sand to clay. Big Cane Alloformation, early—alluvium that is younger than the Avoyelles Alloformation, and is partially buried by Holocene Red River alluvium. It is oldest and highest of two terraces within the Big Cane Alloformation. Possibly it is the meander-belt deposits of a late Pleistocene Red River. It is covered by Peoria Loess. Big Cane Alloformation, late—the younger and lowest of two terraces found within the Big Cane Alloformation within the Big Cane Alloformation. It appears to be a former Red River meander-belt. It is covered by Peoria Loess that is overlain by a veneer of Holocene alluvium. Avoyelles Alloformation—meander-belt deposits of the late Pleistocene Mississippi River terraced above and parallel to its alluvial valley in central Louisiana. Remnants of constructional meander-belt morphology that form the Lafayette meander-belt are preserved. The surface is blanketed by Peoria Loess, and the sediments at the top of the unit range from sand to clay. PRAIRIE ALLOFORMATION, EARLY SANGAMON—older of the Prairie Allogroup temporal phases. A diverse depositional sequence of flood plain, meander-belt, and backswamp deposits of the middle Pleistocene ancestral Mississippi River, Red River, local fluvial equivalents of tributary streams, and coastal plain streams. Where this unit is mapped near the Mississippi River flood plain, it is blanketed by both Peoria and Sicily Island Loess or loess-derived colluvium. The unit dips into the subsurface beneath the Prairie Allogroup, Late Sangamon in the coast-parallel region, but is commonly terraced above it in stream valleys. The sediments are generally clay, silty clay loam, or sandy clay loam, and grade to sand and gravel. Beaumont Alloformation—oldest and topographically highest of the Prairie surfaces west of the Mississippi Alluvial Valley. It exhibits the relict channels of the Red River, and includes deposits of the Ingleside barrier trend west of the Baton Rouge quadrangle. It is composed of coastal plain deposits of late to middle Pleistocene streams. Hammond Alloformation—topographically lowest of the Prairie surfaces east of the Mississippi Alluvial Valley. Within the Baton Rouge 100K geologic quadrangle, its constructional topography lies hidden beneath a thick layer of Peoria Loess. It is composed of coastal plain deposits of late to middle Pleistocene streams. Hac Had Hal Hala Hlm Hld Hll Hmm1 Hmc1 Hmd1 Hml1 Ppav The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government or the state of Louisiana. This map has been carefully prepared from the best existing sources available at the time of preparation. However, the Louisiana Geological Survey and Louisiana State University do not assume responsibility or liability for any reliance thereon. This information is provided with the understanding that it is not guaranteed to be correct or complete, and conclusions drawn from such data are the sole responsibility of the user. These regional geologic quadrangles are intended for use at the scale of 1:100,000. A detailed on-the-ground survey and analysis of a specific site may differ from these maps. 1934 Chacko J. John Director & State Geologist Open Water Contact—includes inferred contacts. Fault—dashed where inferred; dotted where concealed. Streams Roads Topographic contours
Transcript of Baton Rouge 30 x 60 Minute Geologic Quadrangle · BATON ROUGE, LOUISIANA 30091-A1-100K BATON ROUGE,...
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SCALE 1:100,000Base map from U.S. Geological Survey, 1:100,000-scale Digital Line Graphs (100K DLG)
Universal Transverse Mercator Projection, Zone 151927 North American Datum (NAD 27)
Contour Interval 10 metersNational Geodetic Vertical Datum 1929
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BATON ROUGE, LOUISIANA30091-A1-100K
BATON ROUGE, LOUISIANA 30 x 60 MINUTE GEOLOGIC QUADRANGLE SERIES
Baton Rouge 30 x 60 Minute Geologic Quadrangle2000
Produced and published by the Louisiana Geological Survey208 Howe-Russell Geoscience Complex, Louisiana State UniversityP.O. Box G, Baton Rouge, LA 70893 • 225/388-5320 • www.lgs.lsu.edu
Production of this map was supported by the U.S. Geological Survey,Department of the Interior, under Assistance Award No. 1434-93-A-1154 and by the Office of Mineral Resources, Louisiana Department of Natural Resources.
Copyright ©2000 by the Louisiana Geological Survey
Geology by:Paul V. Heinrich and Whitney J. Autin
GIS compilation by:S. Ahmet Binselam and R. Hampton Peele
Cartography by:John Snead and Robert Paulsell
New Roads
Baton RougeCrowley
30°
32°
94° 92° 90°
0 50 miles
Amite BogalusaVille Platte
Pontchatoula
L O U I S I A N A
Published (2000) in production
30 x 60 Minute Geologic Quadrangles
De Ridder
Lake Charles Gulfport
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Correlation of Map Units
Description of Map Units
HOLOCENEUndifferentiated alluvium of small upland streams—alluvial deposits of minor creeks and streams filling valleys cut into older deposits. The modern flood plain within these valleys constitutes the surface of these deposits. The lithology reflects the lithology of the older deposits from which they have been eroded and reworked.
Backswamp deposits—Holocene deposits of the Mississippi and Atchafayala rivers. They consist of fine-grained, usually clayey and often organically rich sediments that underlie flood basins between meander-belts.
Small river deposits, undifferentiated—undifferentiated alluvial deposits of small rivers consisting of recognizable but unmapped natural levees, distributaries, and abandoned channels.
River channel remnants—sinuous tonal pattern interpreted to be an abandoned river channel, buried beneath backswamp and natural levee deposits.
ATCHAFALAYA RIVER DEPOSITS
Crevasse complex of the Atchafalaya River—silty, sometimes sandy, deposits of crevasse splays originating from the Atchafalaya River.
Distributary complex of the Atchafalaya River—silty to sandy, natural levee deposits of distributaries originating from the Atchafalaya River.
Natural levee deposits of the Atchafalaya River—the silty to sometimes sandy overbank deposits that compose the low natural levees that flank the Atchafalaya River.
Lacustrine deposits—fine-grained, generally clayey deposits of areas created by the infilling of lakes by Atchafalaya River distributaries.
LAFOURCHE DELTA LOBE DEPOSITS
Lafourche meander-belt—clayey deposits filling the abandoned main Mississippi River channel of the Lafourche delta lobe. Locally, these deposits may include younger natural levee and overbank deposits of the modern Bayou Lafourche that are too small to map at this scale.
Distributary complex of the Lafourche delta lobe—silty to clayey natural levee deposits of distributaries originating from the Lafourche meander-belt.
Natural levee deposits of the Lafourche meander-belt —the silty to sometimes sandy deposits that compose the low natural levees that flank the Lafourche meander-belt and it's main distributary channels.
MISSISSIPPI RIVER DEPOSITS
Mississippi River meander-belt No. 1—point-bar channel deposits and abandoned channels associated with the modern course of the Mississippi River.
Crevasse complex of Mississippi River meander-belt No. 1—silty to sandy deposits of crevasse splays originating from meander-belt No. 1.
Distributary complex of Mississippi River meander-belt No. 1—silty to clayey, natural levee deposits of distributaries originating from meander-belt No. 1.
Natural levee complex of Mississippi River meander-belt No. 1—silty to sandy overbank deposits that compose the low natural levees flanking the Mississippi River meander-belt No. 1.
Upper (Bayou Teche) occupation of Mississippi River meander-belt No. 3 —point-bar channel deposits associated with the relict Bayou Teche course of the Mississippi River. This is the most recent meander-belt 3 occupation.
Crevasse complex of Bayou Teche meander-belt—silty to sandy deposits of crevasse splays originating from the Bayou Teche occupation of meander-belt No. 3.
Distributary complex of Bayou Teche meander-belt—silty to clayey, natural levee deposits of distributaries originating from the Bayou Teche occupation of meander-belt No. 3.
Natural levee complex of Bayou Teche meander-belt—silty to sometimes sandy overbank deposits that compose the low natural levees that flank the Bayou Teche occupation of meander-belt No. 3.
Distributary complex occupied by the Mississippi and Atchafalaya Rivers—natural levees and abandoned course of a relict distributary system of the Bayou Teche meander-belt. Segments of the abandoned course have been either reoccupied or buried by distributaries of the Atchafalaya River.
Lower (Bayou Portage) meander-belt of Mississippi River meander-belt No. 3 —point bar deposits associated with the relict Bayou Portage occupation of the Mississippi River meander belt No. 3.
Crevasse complex of Bayou Portage meander-belt—silty to sandy deposits of crevasse splays originating from the Bayou Portage occupation of meander-belt No. 3.
Distributary complex of Bayou Portage meander-belt—silty to clayey, natural levee deposits of distributaries originating from the Bayou Portage occupation of meander-belt No. 3.
Natural levee complex of Bayou Portage meander-belt—generally silty overbank deposits that compose the low natural levees that flank the Bayou Portage meander-belt.
RED RIVER DEPOSITS
Meander-belt of the Teche course of the Red River—brownish red point bar and overbank deposits of the relict course of the Red River that have accumulated within the Bayou Teche occupation of Mississippi River meander-belt No. 3. Locally, these deposits may include younger natural levee and overbank deposits of the modern Bayou Teche that are too small to map at this scale.
Natural levee complex of the Teche course of the Red River—scattered natural levee deposits composed of silty, reddish-brown sediments that have locally buried parts of the Bayou Teche natural levees.
Major distributary channel of the Teche course of the Red River—clayey to silty deposits that fill an abandoned Teche–Red River distributary along Catahoula Coulee.
PLEISTOCENE
LOESS
Peoria Loess—Eolian silt veneer of late Wisconsin age mantling Pleistocene strata. Loess is depicted where the total thickness is 1 meter or greater.
PRAIRIE ALLOGROUP
A diverse depositional sequence of late to middle Pleistocene deposits of the Mississippi River, its tributaries, and coastal plain streams; includes terraces, fluvial (meander-belt, backswamp, and braided-stream), colluvial, estuarine, deltaic, and marine units deposited over a considerable part of the late Pleistocene (Wisconsin to Sangamon). Surfaces generally show little dissection and are topographically higher than the Holocene units. Multiple levels are recognized along alluvial valleys and coast-parallel trends. The Prairie is divided into two temporal phases of deposition.
PRAIRIE ALLOGROUP, LATE SANGAMON—younger of the Prairie Allogroup temporal phases. Alluvial deposits of ancestral late Pleistocene streams. In the coast-parallel Prairie the unit consists of meander-belt deposits of the late Pleistocene Mississippi River, and deposits of the late Pleistocene coastal plain streams. Deposits associated with these valleys are commonly found within the upper portions of the drainage basins. The surface is blanketed by Peoria Loess near the loess source (the Mississippi River flood plain), and the sediments at the top of the unit range from sand to clay.
Big Cane Alloformation, early—alluvium that is younger than the Avoyelles Alloformation, and is partially buried by Holocene Red River alluvium. It is oldest and highest of two terraces within the Big Cane Alloformation. Possibly it is the meander-belt deposits of a late Pleistocene Red River. It is covered by Peoria Loess.
Big Cane Alloformation, late—the younger and lowest of two terraces found within the Big Cane Alloformation within the Big Cane Alloformation. It appears to be a former Red River meander-belt. It is covered by Peoria Loess that is overlain by a veneer of Holocene alluvium.
Avoyelles Alloformation—meander-belt deposits of the late Pleistocene Mississippi River terraced above and parallel to its alluvial valley in central Louisiana. Remnants of constructional meander-belt morphology that form the Lafayette meander-belt are preserved. The surface is blanketed by Peoria Loess, and the sediments at the top of the unit range from sand to clay.
PRAIRIE ALLOFORMATION, EARLY SANGAMON—older of the Prairie Allogroup temporal phases. A diverse depositional sequence of flood plain, meander-belt, and backswamp deposits of the middle Pleistocene ancestral Mississippi River, Red River, local fluvial equivalents of tributary streams, and coastal plain streams. Where this unit is mapped near the Mississippi River flood plain, it is blanketed by both Peoria and Sicily Island Loess or loess-derived colluvium. The unit dips into the subsurface beneath the Prairie Allogroup, Late Sangamon in the coast-parallel region, but is commonly terraced above it in stream valleys. The sediments are generally clay, silty clay loam, or sandy clay loam, and grade to sand and gravel.
Beaumont Alloformation—oldest and topographically highest of the Prairie surfaces west of the Mississippi Alluvial Valley. It exhibits the relict channels of the Red River, and includes deposits of the Ingleside barrier trend west of the Baton Rouge quadrangle. It is composed of coastal plain deposits of late to middle Pleistocene streams.
Hammond Alloformation—topographically lowest of the Prairie surfaces east of the Mississippi Alluvial Valley. Within the Baton Rouge 100K geologic quadrangle, its constructional topography lies hidden beneath a thick layer of Peoria Loess. It is composed of coastal plain deposits of late to middle Pleistocene streams.
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The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government or the state of Louisiana.
This map has been carefully prepared from the best existing sources available at the time of preparation. However, the Louisiana Geological Survey and Louisiana State University do not assume responsibility or liability for any reliance thereon. This information is provided with the understanding that it is not guaranteed to be correct or complete, and conclusions drawn from such data are the sole responsibility of the user. These regional geologic quadrangles are intended for use at the scale of 1:100,000. A detailed on-the-ground survey and analysis of a specific site may differ from these maps.
1934
Chacko J. JohnDirector & State Geologist
Open Water
Contact—includes inferred contacts.
Fault—dashed where inferred; dotted where concealed.
Streams
Roads
Topographic contours
