Geobulletin alpha

Source info:

Author:	Hollis
Date:	2016-04-15 17:11:00
Blog:	In the Company of Plants and Rocks
URL:	http://plantsandrocks.blogspot.com/2016/04/on-road-in-nebraska-geo-challenge.html

Summary:

Where on Google Earth (click on image to view).Lynn David met all three of the recent geo-challenges:"Obviously Nebraska.... cannot mistake that bend in the Platte River. #1 Looks like you're on the bluffs above the Niobrara River (one of my favorite rivers) just northeast of the sand hills area, which might make that the Ogallala. Though I keep thinking it shoud be something older in the Arikaree, Laramie or Chadron? #2 Looks to be the Scotts Bluff area which would make it the Tertiary Arikaree and Gering formations sediments which are mostly fluvial or wind-blown in origin with quite a bit of volcano-clastic sediments, probably from Colorado. #3 Never been there. But going to guess it's the Niobrara."Other readers sent correct answers by email, with more praise for the Niobrara River. They're right—it's great for both plants and rocks!Locations are inserted in bold. Posts with more details will follow.• • •Ordered by increasing age of strata:#1 Darker brown is caused by seepage from the base of a super important aquifer. Niobrara National Wildlife Refuge; base of Ogallala Group, above Rosebud Formation (either Arikaree or White River group; geologists disagree).#2 Thousands of immigrants passed by—did any notice the white ash layers and curious wavy contact? Scotts Bluff on the Oregon Trail; Brule (White River) and Gering (Arikaree) formations below and above the mysterious wavy contact (Cindy—currently investigating, more to follow, hopefully).#3 This rock is gray when freshly exposed, weathering to pale yellow or almost white. This is its type area, and its geological period is eponymous as well. Cretaceous Niobrara Chalk at the confluence of the Missouri and Niobrara Rivers.Actually, this photo is in South Dakota (the state line is in the lake).Happy geo-travels!

Content analysis:

Stratigraphic context:

Recognized stratigraphic terms [n]:	Tertiary [1] Ogallala Group [1] Niobrara Chalk [1] Rosebud Formation [1]
Agenames chronostratigraphy [rating]:	Neogene [0.86] Paleogene [0.1] Cretaceous [0.8] Cenozoic [0.88] Mesozoic [0.8] Phanerozoic [0.92] [0.1] Lower Pliocene [0.1] Upper Miocene [0.1] Middle Miocene [0.1] Pliocene [0.1] Miocene [0.67] Upper Cretaceous [0.8] Campanian [0.1] Santonian [0.1] Coniacian [0.1] Turonian [0.1]

Geographic context:

Location	Country	Latitude	Longitude
Chadron	US	42.8269	-103.002
Colorado	US	38.9979	-105.551
Laramie	US	41.3104	-105.585
Missouri	US	38.2589	-92.4366
Nebraska	US	41.5008	-99.6809
Niobrara River	US	42.748	-98.0497
Ogallala	US	41.129	-101.721
Platte River	US	41.088	-100.636
Rosebud	US	38.387	-91.4026
South Dakota	US	44.2126	-100.247
White River	US	43.5673	-100.745

Keywords:

.Happy geo-travels, .Lynn David, base, bend, bluffs, bold, Chadron, click, Colorado., confluence, correct answers, Cretaceous Niobrara Chalk, curious wavy contact, Darker brown, email, favorite rivers, geo-challenge, geo-challenge answers, geological period, geologists, Gering formations sediments, Google Earth, image, immigrants, Laramie, mysterious wavy contact, Nebraska, Niobrara National Wildlife, Niobrara River, Niobrara Rivers.Actually, Niobrara., Ogallala Group, Oregon Trail, Platte River., readers, recent geo-challenges, Refuge, Road, Rosebud Formation, Scotts Bluff area, seepage, South Dakota, state line, strata, super important aquifer, Tertiary Arikaree, type area, volcano-clastic sediments, white ash layers, White River group