260 SCIENCE March 10 1950 Vol 111

tion The anion formed then adds to the carbonyl acetyl chloride in tlie presence of sodium ( 5 ) or by rr

group of the anhydride (or acyl halide) to give the anion arrangement of b-acetoxycrotonic ester (10) shown

r- 0- 1

This addition carballion then loses the acetate ion to form The mechanism proposed indicates that the reaction ir

the ketone more widely applicable than has been realized Decar-

CHCON(CH) cwL-o--coCH ---+ CHCON(CH) CHCOCH + CAPO-0

-CHI or combines with a proton and loses acetic acid Tlie ad- dition of a carbanion formed by decarboxylation to a earbonyl group has been previously observcd (9)

An alternative meclianism regarded a s less likely in view of the expected ease of loss of carbon dioxide postu- lated a s the first step in tlie preceding mechanism is that the acylamino acid undergoes C-acylation a s an active methylene compound This can be visualized a s proceed- ing through the intermediate

in which the carboxyl group may have been converted to a mixed anhydride an anion or an azlactone This is merely a generalization of tlie previously stated azlac-tone mechanism C-Acylation of active methylcne com-pounds has long been known and is illustrated by forma- tion of diacetoacetic ester from acetoneetic ester and

The Pleistocene History of the Mississippi River

William Herbert Hobbs

Ann Arbor Micbigan

The M+ssissippi Rive thrmghrou+ s h u t half ihs-COUPSC now flows within an area that durilig Pleistocene time was invaded by the lobes of four mntincntal glaciers in succession The f i ~ s t (Missourian) second (Iowan) and third (Illinoian) came from an eastern quarter (Wapcllo Lwbes) k t ltthel a h r inuasiiefis of tlm IJlincrh adthe fourth (Wisconsin) glaciation (Mankato Lobes) spread out from the north ( 8 )

The first three of these glacier invasions each caused a large displacement of the pre-Pleistocene Mississippi whatever may then have been i t s position Duriug the deglaciation of each of tliese glaciers which took place only during the warm summer months of caeh year the upper course of the Mississippi River was niargi~lal to a glacier lobe and i t carried vast quantities of cold melt- water a s well a s the meteoric water from surface strea~ns During the winter months however these channels ear-

boxylation as a source of reactive carbanions represertt a class of organic reactions hitherto unappreciated

References 1 ATTIPNKUIBOWIENNT R nnd DI~IIOT I ) PJ G

J chem Roc 1848 310 2 CI~ARIC J R R ChfilrII JOIINSON alld ROBINSON

i s try of penicillin Princeton N J Irincet-or1 I l n i v Press 1040 P 743

C ACtC3 CIELAXDG 11 and NIE~IANN d Amer e h ~ ~ n 1040 71 841

4 DAICIN11 D and WEST R J biol C h ~ r n 1I)PX 78 91 757

5 MICHAELA Ber 1005 38 208s G Wrren R 11 J org Chem 1047 12 43 7 VIIEY 12 11 and BORUN 011 J A)l14T ~llelllS I IC

1048 70 2005 8 - Submitted to J Amcr ehern Soc

R H rind IIORSON Amer chewamp SIJC9 VIIBY 1 11 I 1940 71 2429

10 WIsr~ceNnsW Rpr 1905 38 546

ried only the meteoric water of the surface streams and so shrank to such moderate proportions as to expose a portior~ of the deposits on the bed to the ficree minds off the glacier and so yield a broad but tliili surrounding apron of loess now weathered (gumbotil)

From tlie Mankato lobes of the Late Illiuoian and the Late Wisconsin glaciations the periglacial land surface sloped oahvard giviag rise to lnany aukward-flowing streams of meltwater that coalesccil ncar the glacier front and their floods formed plains of outwash sur-roundiug which were laid down hcary ampposits of loess

Displaced by the several glacier lobcs the courses of tlw marginal melkwater rivers within the skates of Iowa and hIissouri were as shown in Fig 1 they are now revealed by deep trenches cut in the bedrock

Approximately equal volumes of meltwater must have issued from the southern flanks of each of the four gla- ciers in soutliern Illinois Indiana and Ohio but up to the present the courses of these strcams have not been traced except in Ohio (3) T l ~ e corresponding channels in Ilidiana and Illinois will probably be found soon by the ground-water geologists of both federal and state surveys in their now intensified searell for aquifers within the region Wherever these may later be discovered

361 March 10 1950 Vol 111 SCIENCE

FIG1 Map of sontheastern Iowa and northeastern Miusoori to shorn the courses of the three meltwater rivers that bordered the three IVnpetlu glncier lobes of the blissourinn Iovln a~ld enr-IF 11111oi11n Stages during their degluciation Their sires aompared to the present river are indicated by the profiles at the right

their waters must hare discharged into the Mississippi ment these great seasonal meltwater rivers account for near the mouth of the present Ohio River a t Cairo the greatly increased breadth of the Pleistocene chan- More than the softer beds of the Tertiary Gulf Embay- nels of the Lower Mississippi (Fig 2) A generalized

262 SCIENCE McH 10 1950 Vol 111

IO W A N I L L I N O I A N W I S C O N S I N STAGE STAGE STAGE

1 I L

MILES

FIG 2 Maps of the channel of the Mississippi River during each of the four stages of the Pleistocene For the Lower Mississippi the maps by 13 N Fisk (1) have been followed

section of the four successive channels and terraces i n this stitution on the cruise of the Atlant is in February and lower section of the river has been supplied by Fisk (1) March of 1947 Over large areas in the Gulf of Mexico

The alternation of great volumes of cold summer melt- off the mouth of the Mississippi were found sediments water with much reduced discharges of the Mississippi of varvelike alternations of sand silt and mud which during the winter seasons throughout the Pleistocene pe- were characterized by a subarctic fauna These the far-riod is confirmed by the bottom cores and oceanographic spread bottom-set beds of the delta were found within samples collected by the Woods Hole Oceanographic In- one or two feet of the surface of the sea floor (4)

References

1 FISK IIAROLD Geological investigatiow op t l ~ e 3 VEB STEEG KARL and LAMB QeolN alluvial SPOUT WILBUR G F valley of the Lower Mississippi Riaer U S Army Survey of OMo 1943 Bull 44 Chap 11 and map Corps of Engineers 1944 1 78 opposite page 78

2 HOBBS WIILIAN 11 Glacial studies of the pleistocenc o f 4 TRASIC PAnKER D STETSONIIENRYC and IHLEGER North An~crica An11 Arbor Edwards Bros 1947 FEEDB Ja Bull geol Soc Amer 1947 1233 Pp 66-102 Papers read a t Ottawa meeting

262 SCIENCE McH 10 1950 Vol 111

IO W A N I L L I N O I A N W I S C O N S I N STAGE STAGE STAGE

1 I L

MILES

FIG 2 Maps of the channel of the Mississippi River during each of the four stages of the Pleistocene For the Lower Mississippi the maps by 13 N Fisk (1) have been followed

section of the four successive channels and terraces i n this stitution on the cruise of the Atlant is in February and lower section of the river has been supplied by Fisk (1) March of 1947 Over large areas in the Gulf of Mexico

The alternation of great volumes of cold summer melt- off the mouth of the Mississippi were found sediments water with much reduced discharges of the Mississippi of varvelike alternations of sand silt and mud which during the winter seasons throughout the Pleistocene pe- were characterized by a subarctic fauna These the far-riod is confirmed by the bottom cores and oceanographic spread bottom-set beds of the delta were found within samples collected by the Woods Hole Oceanographic In- one or two feet of the surface of the sea floor (4)

References

1 FISK IIAROLD Geological investigatiow op t l ~ e 3 VEB STEEG KARL and LAMB QeolN alluvial SPOUT WILBUR G F valley of the Lower Mississippi Riaer U S Army Survey of OMo 1943 Bull 44 Chap 11 and map Corps of Engineers 1944 1 78 opposite page 78

2 HOBBS WIILIAN 11 Glacial studies of the pleistocenc o f 4 TRASIC PAnKER D STETSONIIENRYC and IHLEGER North An~crica An11 Arbor Edwards Bros 1947 FEEDB Ja Bull geol Soc Amer 1947 1233 Pp 66-102 Papers read a t Ottawa meeting