:U)7 



Sinn of tliciii is not iiitcnili'd here. Such would cill Cm- ;i (IcMilcd t<ip(i- 

 Kni|»l''<' '"•■'I' ">" 'li«' i-nlirc ic;,'i(iii. Tiic l(p])(>iir;i|>iijc (•(uidilidii is very iii;idc- 

 (luatcly pi-csciiici! mi the ucncrnl in;iii. Tiic clrv .it inns ^ivcn iicrc iind 

 tluM-o. tile presence and iiosition nf riie KMoi)sl()Me esciii'pnient. tlie drainajje 

 lines, and tlie inserted j:t'<»l<>Ki<' and toiiofirapliii- cross-section slutw the main 

 elements. Wliere some considerable detail is Kiven, a topographic iiiap 

 has been prepared. 'I'liis small bit of the larger area is presented in detail 

 In re\('al a particnlai- condition. The I'Xplanation of tlii' pre-eiit topo- 

 trraiihic condition of the area emphasizes lithnlo.siv. since the litlmlngic 

 units largely control the topography. 'I'lie time factors or elements will 

 be little more than mentioned, except where the explanation offered is 

 one which has never been brought to the attention of pliysiographers pre- 

 vious to this ]ii-esentatioii. 



hifli(( lice (if Lilholdfi!/. 



The .\(>w Albany black shale and the sandy shale and muddy sandstones 

 of the Knobstone group belong to the cla^s of non-n-sistant rocks. Tliey 

 weather very rapidly by altei'nate fi'ee/.ing and thawing. The fragments 

 given up by the freezing and thawing method of weathering are readily 

 carried away by the sti'eams of running water. These roclvs al.so are 

 easily corroded by running water. Streams even of small size in these 

 rocks have reached grade clo.-e up to their sources. As a result 

 of this, streams heading in a I'egion where these rooks are relatively 

 lii.gh above local base level havt' a veiy precipitous descent at their very 

 headwaters, i)ut soon take on a relatively flattened gradient within a 

 short distance from their over-steepened heads. The upper part of the 

 knobstone. however, consists of a relatively large anu)unt of massive im- 

 pure sandstone. It is much nuu'e resistant than the lower Knobstone 

 rocks. Only very locally, however, does this upper portion resist weather- 

 ing sufficiently to stand as vertical cliffs. It may be said that the great 

 thickness of Knobstone rocks with the correspon<ling rather wide areal 

 outcrop does not result in the formation of cliffs. But the outcrop con- 

 sists of (juite steep slopes, often attaining 80 degrees or more from the 

 horizontal.- 



The Ilarrodsburg limestone immediately over-lying the Knol>stone is 

 much more resistant to mechanical denudation, and the interstream spaces 

 are often gently rolling tra<-ts. Whei-e the streams lia\-e cut through the 

 Ilarrodsburg caiiping of the Knob-tone, tougue-like upland ti-acts are 

 borilered by the steep slojies leading abrni>tly to the Knobstoni" valleys. 

 The limestone is soluble in meteni-ic watei-s and since it is bedded and 

 jointed, sink-holes are (|ui1c common. 'I'he Knobstone-IIari-odsburg contact 

 is conse(piently a spring horizi.n of some imiiortance. The Ilarrodsburg is 



-Vor wpathcrnig iiiid enisioii of Kiiolistniic nxUs. sec tlir rollowiiig rofcrciici's : 

 .r. F. Nowsoin. A ricologic .-uid To]n>>ifai)hic Section Across Soutlicrn Indiana. 2<itli 

 Annual Uoport. Iiul. Dopt. of GpoI anil Natural Res. liMil. |.p. 2i\r>'2~:i. G. II. Ash- 

 ley, Gcolofry of tli<' Lower Carboniferous Area of Sontlieni Imliana. Inil. Dept. of 

 Geol. anil Natural Kes. 1902. pp. 54-oS. E. R. Cummings. The Geological Conditions 

 of Municipal Wflt<»r Suppl.v in the Driftless Area of Southern Indiana, Proceedings 

 of the Ind. Acad, ot Science, 1911, p. 114-124. 



